JP2007013640A - Image processor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To perform quick calculation of average errors in image processing by error diffusion method. <P>SOLUTION: The average error calculating section 22 of an image processor comprises multiplication sections 26a-26g and summing memories 32a-32g, arranged in correspondence with the array of neighborhood pixels. These multiplication sections multiply the error values ΔY<SB>0</SB>and ΔY<SB>1</SB>of foremost pixels in the array of neighborhood pixels and weighting factors Ka-Kg set for respective neighborhood pixels. These summing memories perform processing for storing the sum of a stored value, arranged on its rear side and a multiplication value at a corresponding multiplication section. Processing of these summing memories are performed sequentially from ones 32e and 32g located in front toward ones 32a and 32f located in the rear, and stored values located in the forefront are summed by a final adder 36 as an average error. With such an arrangement, the number of processing clocks can be decreased, as much as possible, in the calculation processings of the average error of neighborhood pixels. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image processing apparatus for converting image data by image processing according to an error diffusion method.

The error diffusion method is a technique used when converting image data of an image read by a scanner or the like into image data for reproducing the image by a printer or the like. Pixels expressed as gradations As a technique that can be applied to the conversion from original image data consisting of values to converted image data consisting of pixel values that have been multi-valued (a concept that includes binarization), and that can reproduce a good halftone image Has already been widely used. Image processing according to this error diffusion method is described, for example, in the following patent document.
JP-A-6-284291

  As the operation of image reading devices, image forming devices, etc. increases in speed and accuracy, image data conversion processing is always required to be executed at a higher speed and less burdensome. Along with the cost reduction of equipment, it is desired that the apparatus that performs the conversion process is also lower in cost. This also applies to an apparatus that executes image processing in accordance with the error diffusion method, and various improvements to the image processing apparatus lead to an improvement in the practicality of the apparatus. In view of such a situation, an object of the present invention is to provide an image processing apparatus with high practicality.

  In order to solve the above-described problems, an image processing apparatus according to the present invention is an apparatus that performs image processing by an error diffusion method, more specifically, image data conversion processing, and is used for converting a pixel value of a target pixel. The average error value calculation unit of a plurality of neighboring pixels set in the vicinity of the pixel is virtual corresponding to the arrangement of the plurality of neighboring pixels in the previous line of the pixel line where the target pixel exists. The plurality of multiplication units and the plurality of addition storage units that are arranged in the same manner, and each of these multiplication units is an error of the foremost pixel in the direction in which the conversion process proceeds among the pixels near the previous line The value is multiplied by the weighting coefficient set for each of the pixels in the vicinity of the previous line, and the addition storage unit is based on the storage value of the one arranged behind itself and the multiplication unit corresponding to itself. It is assumed that the process of adding and storing the arithmetic value is performed, and the plurality of addition storage units are executed in order from the one located at the front, whereby the forefront of the addition storage units The average error value of the plurality of neighboring pixels is calculated on the basis of the stored value located in the area.

  In the conventional image processing apparatus, the average error value is calculated by multiplying the error value of each pixel in the vicinity of the previous line by the weighting coefficient and summing the multiplication values for each process for the target pixel. On the other hand, the image processing apparatus according to the present invention is configured to cumulatively add multiplication values due to the above-described configuration. Therefore, it is possible to reduce the number of clocks required for the calculation process of the average error value, and the circuit configuration can be simplified. As a result, the present image processing apparatus becomes a highly practical image processing apparatus. The specific configuration and operational effects of the image processing apparatus of the present invention will be described in detail in the following [Aspect of the Invention] section.

Aspects of the Invention

  In the following, some aspects of the invention that can be claimed in the present application (hereinafter sometimes referred to as “claimable invention”) will be exemplified and described. As with the claims, each aspect is divided into sections, each section is numbered, and is described in a form that cites the numbers of other sections as necessary. This is merely for the purpose of facilitating the understanding of the claimable inventions, and is not intended to limit the combinations of the constituent elements constituting those inventions to those described in the following sections. In other words, the claimable invention should be construed in consideration of the description accompanying each section, the description of the embodiments, etc., and as long as the interpretation is followed, another aspect is added to the form of each section. In addition, an aspect in which some constituent elements are deleted from the aspect of each item can be an aspect of the claimable invention.

  The following items (1) and (2) are not aspects of the claimable invention, but are aspects in which the constituent elements that are the premise of the claimable invention are listed, and any of these terms is cited (11) The aspects of the items (16) to (16), the aspects (21) to (40), and the aspect (51) are various aspects of the claimable invention. By the way, in each of the following terms, the term (11) that cites the term (2) corresponds to claim 1, and the combination of the terms (12) and (13) corresponds to claim 2 and (14) The term corresponds to claim 3, the (15) term corresponds to claim 4, and the (16) term corresponds to claim 5.

(1) An image processing apparatus used for converting image data of a source image composed of a plurality of pixels defined as a certain matrix into image data of a converted image by processing according to an error diffusion method,
The pixel value of each of the plurality of pixels of the image constituting the image data of the original image, the pixel value of each of the plurality of pixels of the image constituting the image data of the original image and the converted image When the value is defined as a converted pixel value and a process for one pixel according to the error diffusion method as a unit process,
Unit processing is performed on a target pixel that is one pixel existing on a target line that is one of the pixel lines in the matrix, and the converted pixel value of the target pixel is based on the source pixel value of the target pixel. And a unit processing execution unit for obtaining a conversion error value,
While the target pixel is sequentially shifted toward the front in the line direction, one-line processing in which unit processing by the unit processing execution unit is repeated for the target line is executed, and the target line is sequentially shifted. An image processing apparatus that converts the image data of the original image into the image data of the converted image by repeating the one-line process while being performed.

  The aspect described in this section is a precondition of the claimable invention as described above. Although the specific method of “processing according to the error diffusion method” in this section is not particularly limited, it is called “target pixel” (referred to as “target pixel”) which is one image constituting the original image. It is only necessary that the above “unit processing”, which is a series of processes, is executed every time, and as the unit processing, for example, a pixel that has already been subjected to unit processing existing in the vicinity (periphery) of the target pixel. The pixel value of the target pixel is corrected based on the average error obtained by averaging the errors caused by the multi-value conversion, and the corrected pixel value is compared with a threshold value set for multi-value conversion. A process of determining the “converted pixel value” converted into a multi-value and calculating the “converted error value” of the target pixel from the converted pixel value and the corrected pixel value Can do. Then, the unit processing is repeated as described above, and the above-mentioned “original image image data” (hereinafter, also referred to as “original image data”), which is the original image data, is converted into an image after conversion processing. The process may be such that the data is converted to the above-described “converted image image data” (hereinafter also referred to as “converted image data”).

  In the aspect of this section, the “primary pixel value” is a value determined on the basis of an optical characteristic value for each pixel read by a scanner, a digital camera, or the like. Any value can be used as long as it is expressed as a gradation, for example, a discrete value such as 0 to 255 or a continuous value. Moreover, the pixel value after performing filter processing, such as smoothing and edge emphasis, on those pixel values may be used. On the other hand, the “converted pixel value” is a value obtained by converting the original pixel value by the unit processing, and may be, for example, a value that is multi-valued into two values or multi-valued into three or more values. It may be a value. The “line direction” refers to one of the two directions when the pixels are arranged in a matrix in two directions in which the original image and the converted image intersect each other, that is, a matrix, When defined by columns, this is the direction in which the pixels constituting one of the rows and columns are arranged. In the aspect of this section, in a word, scanning is performed in the line direction, and scanning of the line of one pixel in the direction of the line is completed, and scanning is performed in a direction crossing the line direction, and image processing is performed. Therefore, the line direction can also be referred to as a main scanning direction, and a direction intersecting the line direction (hereinafter also referred to as “column direction”) can also be referred to as a sub-scanning direction. Incidentally, “front” in the line direction and the column direction means the direction in which the unit processing and the one-line processing proceed, respectively, and “backward” means the direction opposite to the direction in which those processing proceeds. Shall.

  The image processing according to the aspect of this section may be executed when the original image data after creation is converted into converted image data. That is, for example, it may be executed to convert the original image data filed into converted image data in a batch process. Further, it may be executed when the original image data being created is sequentially converted into converted image data. That is, for example, in the process in which the original image data is created while being read by a scanner or the like, the image data is sequentially converted each time image data for some pixel lines of the original image data is created. It may be executed in parallel with processing (hereinafter also referred to as “sequential processing”), that is, reading with a line scanner or the like. In the case of the sequential processing, for example, the direction corresponding to the direction in which the light receiving elements of the scanner are arranged can be set as the main scanning direction, and the direction corresponding to the moving direction of the scanner head can be set as the sub scanning direction. .

  In terms of hardware, the image processing apparatus according to the aspect of this section may be configured as a dedicated electronic circuit or electric circuit, or may be configured mainly by a computer. When the computer is the main component, the image processing can be realized by executing a dedicated image processing program by the computer.

(2) A plurality of pixels, each of which is set in the vicinity of the target pixel in the matrix and whose conversion error value is used to obtain the conversion pixel value of the target pixel, is defined as a plurality of error use pixels. If
The unit processing execution unit
Conversion of each of a plurality of pixels on the previous line that are a plurality of pixels set to be continuous with each other on the target line in the previous one-line process and are at least part of the plurality of pixels using the error An average error calculation unit that calculates an average error value of the plurality of error use pixels based on an error value;
The original pixel value of the target pixel is corrected based on the average error value calculated by the average error calculation unit, and the converted pixel value of the target pixel is acquired based on the pixel value obtained by the correction. The image processing apparatus according to item (1), which is configured in (1).

  In the image processing according to the error diffusion method, when determining the conversion pixel value of the target pixel, the conversion error value of a pixel in the vicinity of the target pixel, that is, a peripheral pixel that has already been subjected to unit processing is calculated. An averaged average error value is used. The image processing apparatus according to the aspect of this section is an aspect including a functional unit that calculates the average error value. The above-mentioned “error use pixel” is the above “previous line error use pixel”, that is, only a plurality of pixels on a line of pixels on which the previous one-line processing has been executed (hereinafter, also referred to as “previous line”). It is not limited to what is comprised by. For example, as will be described later, it may be configured to include one or more pixels on a line of pixels currently being subjected to one-line processing (hereinafter also referred to as “the line”). Good. Further, it may be configured to include one or more pixels on a line of one or more pixels that have been subjected to one line processing before the previous line. The “average error value” in the aspect of this section means an average value obtained by weighting each pixel value of the error utilization pixels. An appropriate weight can be adopted according to the configuration of the error utilization pixel. Incidentally, it is also possible to obtain a simple averaged average error value by making the weighting for each pixel value uniform.

(11) In the case where the foremost error use pixel on the previous line is defined as the foremost error use pixel on the previous line among the plurality of previous line error use pixels,
The average error calculator is
Virtually arranged in the line direction, and executes a multiplication process of each of the weighting coefficients set corresponding to each of the plurality of previous line error use pixels and the conversion error value of the foremost error use pixel on the previous line. A plurality of front line multipliers corresponding to the number of pixels on the previous line error-use,
When there are those arranged on the rear side nearest to each of the plurality of front line multipliers, the stored value of each and the plurality of front line multipliers are provided. And adding and storing the result value of the multiplication process by the one corresponding to itself, and when there is no one arranged on the rear side of itself, it is stored in the plurality of front line multiplication units. A plurality of previous-line addition storage units corresponding to the number of the previous-line error-use pixels in which the result values of multiplication processing by corresponding ones are stored;
The processing by each of the plurality of previous line addition storage units is configured to be executed sequentially from the processing by the one arranged in front, and the storage of the foremost one of the plurality of previous line addition storage units is stored. The image processing device according to item (2), configured to calculate the average error value based on a value.

  The mode described in this section is a mode aimed at improving the calculation process of the average error value. In the conventional image processing apparatus, for each unit process for the target pixel, the conversion error value of each of the pixels on the previous line error is multiplied by the weighting coefficient set for each of the pixels, and the multiplication is performed. At least a part of the average error value is calculated by adding the respective values. Therefore, in the case where the image processing apparatus is composed mainly of an electronic circuit and an electric circuit, the unit obtained by multiplying the conversion error value and the weighting coefficient for each unit process is temporarily stored and stored. In addition to a plurality of registers for storing the results of the multiplication, a register for addition is also required, which complicates the circuit configuration and average error. Since the number of clocks for the value calculation process needs to be at least the number of clocks corresponding to the number of pixels on the previous line error, the processing time is long. On the other hand, in the aspect described in this section, a unit obtained by multiplying the conversion error value of one of the previous line error using pixels by each of the weighting coefficients set for the number of the previous line error using pixels is a unit. Since it is possible to configure a register that cumulatively adds as the processing proceeds, it is possible to simplify the circuit configuration by reducing the number of registers, and the clock required for calculating the average pixel value In extreme terms, the number can be one clock.

  Note that “virtually arranged in the line direction” in this section does not mean that the preceding line multiplying units are actually arranged in that direction, but the preceding line multiplying units are not arranged. Means that the pixels on the previous line error use correspond to each other, the correspondence between the multiplication unit and the weighting coefficient set for each of the previous line error use pixels, and the result of the multiplication process by which multiplication unit This is a concept introduced in terms of convenience in order to define a correspondence relationship in which the value is added to the stored value of the previous line addition storage unit and stored in which previous line addition storage unit. By the way, in the correspondence of this section, the result value of the multiplication processing by each of the front line multiplication units is forwarded from the rear side in the virtually arranged direction by the front line addition storage unit as the unit processing proceeds. In other words, it is added in the same direction as the direction of transition of the target pixel.

(12) The average error calculation unit
Further, the one or more pixels set to be continuous with the target pixel on the rear side in the line direction on the target line, and one or more on-line error use that is a part of the plurality of error use pixels The image processing apparatus according to item (11), wherein the average error value is calculated based on the conversion error value of each pixel.

(13) The average error calculation unit
Each of the weighting coefficients that are virtually arranged in the line direction and are set corresponding to each of the one or more on-line error use pixels, and the conversion error value of the pixel located immediately behind the target pixel, A number of one or more corresponding line multiplying units corresponding to the number of the one or more on-line error utilizing pixels for executing the multiplication processing of
If there is one that is arranged corresponding to each of the one or more multiplication units for the line, and each of them is arranged in the immediate rear side, the stored value and the one or more for the line The result value of the multiplication process by the one corresponding to itself among the multiplication units is added and stored, and when there is no one arranged behind the multiplication unit, one of the one or more corresponding line multiplication units A number of one or more addition storage units for the line corresponding to the number of the on-line error utilization pixels of one or more of which stores the result value of the multiplication process by the one corresponding to itself,
The processing by each of the one or more line addition storage units is configured to be executed sequentially from the processing by the one arranged in front, and the forefront of the one or more line addition storage units. The image processing device according to item (12), which is configured to calculate the average error value based on a stored value.

  The modes described in the above two sections are modes in which error-utilizing pixels are set on the line that is the pixel line for which one-line processing is currently being performed. The latter in these two terms is a mode in which the same processing as the above-described calculation processing for the on-line error use pixel is performed on the on-line error use pixel, and the above calculation processing is performed. The same merit as in the case of being executed is obtained for the processing for the on-line error utilization pixel.

  (14) The average error calculation unit sums the stored value of the foremost one of the plurality of previous line addition storage units and the stored value of the foremost one of the one or more line addition storage units. The image processing apparatus according to item (13), wherein the image processing apparatus is configured to calculate the average error value as the average error value.

  The mode described in this section is an effective mode in the case where the error use pixel is composed of only the previous line error use pixel and the on-line error use pixel.

  (15) Each time the unit processing is executed by the unit processing execution unit, the image processing apparatus receives a conversion error value of one pixel that becomes the foremost error use pixel on the previous line (11) Item 14. The image processing device according to any one of Items 14 to 14.

  In the conventional image processing apparatus described above, the conversion error value of each of the previous on-line error utilization pixels is multiplied by the weighting coefficient for each unit process for the target pixel. Therefore, for example, when the conversion error value of the pixel in the previous line where the unit processing has already been completed is input from the outside of the image processing apparatus, it is necessary to input the conversion error value for a plurality of pixels. Therefore, the input processing is complicated, and this is a factor that hinders improvement in the speed of image processing. On the other hand, in the above-described mode in which only the converted pixel value of the foremost pixel on the previous line is multiplied by the weighting coefficient, only the converted pixel value of the foremost pixel needs to be input for each unit process. It will be. The aspect described in this section is an aspect in view of that, and according to the aspect of this section, it is possible to simplify the input process of the conversion error value, thereby speeding up the image processing. Is possible.

  (16) The image processing device according to (15), wherein the conversion error value of the target pixel is output each time the unit processing is executed by the unit processing execution unit.

  The conversion error value of the pixel for which the unit processing has been completed becomes the error utilization pixel on the previous line in the next one-line processing. In view of this, the aspect described in this section is an aspect in which the conversion error value of the target image is output for each unit process. When the converted pixel value is stored in a storage unit provided outside the image processing apparatus, in the aspect of this section, a conversion error value of one pixel is input for each unit process, and one The conversion error value of the pixel is output, and the input / output processing of the conversion error value is simplified.

(21) The image processing apparatus is
The image data of the original image is composed of a plurality of pixels defined as another matrix interpolated by pixel lines while supplementing pixels between the matrix lines of the original image, which is the matrix. It is used to convert to converted image data,
Each line of pixels in the matrix of pixels of the source image that is also present in the matrix of pixels of the converted image is represented by a source line and a pixel of the source image corresponding to the source line. In the case where the pixel line for interpolating the matrix is defined as the interpolation line,
One source line is set as the target line, a first target pixel that is one pixel existing on the target line is set as the target pixel, and unit processing is performed on the first target pixel, and the first target pixel is executed. A first unit processing execution unit as the unit processing execution unit for obtaining a converted pixel value and a conversion error value of the first target pixel based on a primitive pixel value of the pixel;
The original pixel value of the first target pixel before this time, which is set as the first target pixel in one unit processing executed before this time by the first unit processing execution unit, on the interpolation line corresponding to the target line, While using the conversion error value of the first target pixel acquired by the first unit processing execution unit based on the pixel value as the pixel value of the second target pixel associated with the first target pixel, A second unit processing execution unit that executes unit processing for the second target pixel and acquires a converted pixel value of the second target pixel;
The unit processing by the first unit processing execution unit and the unit processing by the second unit processing execution unit are respectively performed while the first target pixel and the second target pixel are sequentially shifted toward the front in the line direction. The image processing apparatus according to (1), wherein the one-line process is repeated for the target line and the interpolation line.

  Conventionally, when creating a converted image in which pixel lines are interpolated in the sub-scanning direction described above, first, another original image obtained by interpolating pixel lines between the lines of the original image (hereinafter referred to as “interpolated source image”) Is created, and the converted image is created by executing image processing according to the error diffusion method for the interpolated original image. In such conventional processing, for example, when batch processing is performed, a large-capacity memory is required to store the interpolation original image. Further, even when the above-described sequential processing such as reading in parallel with reading of image data by a line scanner or the like is performed, for example, when the above-described filter processing such as smoothing is performed on the original image. Due to the fact that the pixel values for a plurality of pixel lines must be accessed every time one pixel is filtered, the burden of performing the process of creating the interpolation source image while performing the filtering process is large. Therefore, it is difficult to perform the image processing at a high speed. In view of such a situation, the aspect described in this section has an object to make it possible to easily create a converted image that is line-interpolated in the sub-scanning direction.

  In short, the image processing apparatus according to the aspect of this section includes two unit processing execution units that execute the unit processing described above, and the first unit processing execution unit that is one of the two unit processing execution units includes: A unit process for one pixel on the target line in the source image is executed, and the second unit process execution unit, which is the other of the two unit process execution units, interpolates the source pixel value in the process by the first unit process execution unit A unit process is executed for one pixel, assuming that it is the original pixel value of one pixel on the line. Therefore, a converted image value for one pixel on the target line and one pixel on the interpolation line is obtained by a series of unit processes of the two unit processing execution units. Accordingly, it is possible to easily perform image processing according to the error diffusion method while performing line interpolation.

  The “first target pixel before this time” in the aspect of this section may be the target of the current unit processing in the first unit processing execution unit, and is the target of the unit processing before the previous time. It may be a thing. In the former case, by a series of processes of the first unit process execution unit and the second unit process execution unit, two pixels in the same column, that is, two pixels in the same order in the line of pixels in the line direction are primitive. The pixel value is converted into a converted pixel value. On the other hand, in the latter case, the target pixel on the interpolation line is a pixel located on the rear side in the line direction with respect to the target pixel on the target line. That is, the primitive pixel value of the pixel on the interpolation line is converted with a delay from the pixel value of the pixel on the target line.

  In addition, although this term is an expression for performing interpolation of pixel lines by one interpolation line, it does not exclude an aspect of performing interpolation by two or more interpolation lines. That is, for example, the number of pixels in the line direction (corresponding to the number of columns) in the main scanning direction is 600 pixels, and the number of pixels in the column direction (corresponding to the number of lines) in the sub-scanning direction is 300 pixels. The original image data (hereinafter sometimes referred to as “600 × 300”) is converted not only to 600 × 600 converted image data but also to converted image data such as 600 × 600, 600 × 900. It is also possible to apply to this. Specifically, for example, on the target line, a primitive pixel that was set as the first target pixel before this time, that is, a pixel that was set as the second target pixel before this time on the interpolation line is set as the third target. As a pixel, it is possible to adopt a mode in which a third unit processing execution unit that acquires the converted pixel value of the pixel based on the pixel value is further provided. According to this aspect, it is possible to perform image processing according to the error diffusion method while supplementing a further interpolation line different from the interpolation line.

  (22) Each time the unit processing is executed by the first unit processing execution unit, the image processing apparatus receives a source pixel value of one pixel serving as the first target pixel, and executes the unit processing and the first The image processing device according to item (21), wherein each time the unit processing is performed by the two unit processing execution unit, the converted pixel value of each of the first target pixel and the second target pixel is output.

  According to the aspect described in this section, pixel value input / output processing for the image processing apparatus is simplified. In other words, as described above, even when sequential processing is executed, it is only necessary to input a primitive pixel value for each pixel into the image processing apparatus without supplementing pixels in advance, and pixel value input processing Is particularly convenient. Further, for example, even when the above filter processing is executed, it is not necessary to supplement the pixel at the stage of the filter processing, so that the burden of the filter processing can be reduced and the speed of the entire image processing can be reduced. It is possible to improve.

(23) The first target pixel before the current time is the first target pixel in one unit process executed before the previous time by the first unit processing execution unit;
Until the unit processing is executed by the second unit processing execution unit using the original pixel value of the first target pixel before this time as the pixel value of the second target pixel. The image processing device according to (21) or (22), further comprising a primitive pixel value temporary storage unit for storing.

  The mode described in this section is an effective mode in the case where the pixel that is the target of unit processing on the interpolation line is located behind the pixel that is the target of unit processing on the target line in the line direction. Become. Even in such a case, according to the image processing device of the aspect of this section, the primitive pixel temporary storage unit may be a considerably small memory or a small register, and the configuration of the image processing device can be simplified. It will be planned. Note that the aspect of this section is particularly effective in an aspect in which only one primitive pixel value is input for each unit process.

(24) A plurality of pixels, each of which is set in the vicinity of the second target pixel in the pixel matrix of the converted image and uses its own conversion error value to obtain the converted pixel value of the second target pixel Is defined as a plurality of second error utilization pixels,
The second unit processing execution unit is
The plurality of pixels set on the target line and the plurality of pixels based on the conversion error values of each of the plurality of second previous line error using pixels that are at least part of the plurality of second error using pixels. A second average error calculation unit that calculates a second average error value that is an average error value of the second error-utilizing pixels.
The pixel value of the second target pixel is corrected based on the second average error value calculated by the second average error calculation unit, and the pixel value of the second target pixel is corrected based on the pixel value obtained by the correction. Configured to obtain a transformed pixel value;
The second average error calculation unit uses the conversion error value of the first target pixel as the conversion error value of one of the plurality of second previous-line on-line error use pixels, and performs the second average error calculation. The image processing device according to any one of items (21) to (23), configured to calculate an error value.

  The mode described in this section is a mode in which the unit processing for the second target pixel is limited with respect to the average error value calculation processing. Specifically, the error use pixel on the previous line among the error use pixels for the target pixel is the pixel on the target line, and the conversion error value obtained by the unit processing for the first target pixel this time is More specifically, in more detail, the conversion error value is used without being input from the outside of the image processing apparatus. According to the aspect of this section, for example, the conversion error value of the first target pixel can be used in the unit process for the second target pixel that is continuously performed. It is possible to simplify the process flow of the apparatus, specifically, the transfer of pixel values from the first unit processing execution unit to the second unit processing execution unit.

(25) The second unit processing execution unit further acquires a conversion error value of the second target pixel by the unit processing for the second target pixel.
The second average error calculation unit further includes one or more pixels set to be continuous with the second target pixel on the back side in the line direction on the interpolation line, and the plurality of second error use pixels. The image processing device according to item (24), wherein the second average error value is calculated based on the conversion error value of each of the one or more second on-line error utilization pixels that are a part of the image error.

  The mode described in this section is a mode in which the error utilization pixel for the second target pixel also includes a pixel on the interpolation line as the line.

(26) The plurality of second previous-line error use pixels are set as a plurality of pixels that are continuous with each other,
A second unit processing execution unit configured to convert a conversion error value of the first target pixel to a foremost error use pixel on the second previous line that is positioned in the forefront in a line direction among the plurality of second use errors on the previous line; The image processing apparatus according to (24) or (25), wherein a unit process is performed on a pixel that can be used as a conversion error value as the second target pixel.

  The mode described in this section is a mode in which the positional relationship between the first target pixel and the second target pixel in the line direction is limited. More specifically, for example, the conversion error of the first target pixel in the current unit processing In a mode in which the positional relationship between the two target pixels is limited so that the value is used as the conversion error value of the forefront error pixel for the second target pixel in the unit processing after this time. is there. As will be described later, this is particularly effective when the above average error value calculation processing is applied to the unit processing for the second target pixel.

(27) The second average error calculation unit includes:
Each of the weighting coefficients that are virtually arranged in the line direction and are set corresponding to each of the plurality of second previous line error using pixels and the conversion error value of the second previous line first error using pixel A plurality of second front line multiplying units corresponding to the number of the plurality of second front line error-utilizing pixels for performing the multiplication process;
When there is a plurality of second front line multiplying units provided corresponding to each of the plurality of second front line multiplying units, each of which is arranged on the rear side closest to the second front line multiplying unit, the stored value and the plurality of second front lines are stored. The result value of the multiplication process by the one corresponding to itself among the line multipliers is added and stored, and when there is no line arranged behind the line multiplication unit, the plurality of second front line multiplications A plurality of second front-line addition storage units corresponding to the number of the second previous-line on-line error use pixels that store the result value of the multiplication process by the one corresponding to itself. Have
The processing by each of the plurality of second previous line addition storage units is configured to be executed sequentially from the processing by the one arranged in front, and among the plurality of second previous line addition storage units, The image processing device according to item (26), which is configured to calculate the second average error value based on a stored value of the previous one.

(28) The second unit processing execution unit further obtains a conversion error value of the second target pixel by the unit processing for the second target pixel,
The second average error calculation unit is
Further, the one or more first pixels that are set to be continuous with the second target pixel on the rear side in the line direction on the interpolation line and are a part of the plurality of second error utilization pixels. 2 The second average error value is calculated based on each conversion error value of the on-line error utilization pixel,
Each of the weighting coefficients that are virtually arranged in the line direction and are set corresponding to each of the one or more second on-line error use pixels and pixels that are positioned immediately behind the second target pixel A number of one or more second line multiplication units corresponding to the number of the one or more second line error utilization pixels that perform the multiplication process with the conversion error value;
If there is one that is arranged corresponding to each of the one or more second line multiplying units, and each of them is arranged in the immediate rear side of itself, the stored value of itself and the one or more first 2 The result value of the multiplication processing by the one corresponding to itself among the multiplication units for the line is added and stored, and when there is no one arranged on the rear side of the line, the one or more second relevant values The number of one or more second corresponding lines corresponding to the number of the one or more second on-line error utilization pixels that store the result value of the multiplication processing by the line multiplier corresponding to itself. An addition storage unit;
The processing by each of the one or more second relevant line addition storage units is configured to be executed sequentially from the processing by the one arranged in front, and further, the one or more second relevant line addition storage units. The image processing device according to item (27), configured to calculate the second average error value based on a stored value of the previous one of the two.

  (29) The second average error calculation unit may store a storage value of the foremost one of the plurality of second previous line addition storage units and a forefront of the one or more second line addition storage units. The image processing apparatus according to item (28), configured to calculate a sum of stored values as a second average error value.

  The modes described in the above three terms are various modes in which the characteristic average error value calculation process described above is applied to the unit process for the second target pixel. The configuration related to the average error value calculation processing described in the above three terms is the same as the configuration related to the processing described above, and thus the description thereof is omitted here. In addition, the merit by the said process demonstrated previously will be enjoyed also in the aspect of said three term.

(30) A plurality of pixels, each of which is set in the vicinity of the first target pixel in the matrix of pixels of the converted image and whose conversion error value is used to obtain the converted pixel value of the first target pixel Is defined as a plurality of first error use pixels,
The first unit processing execution unit
A plurality of pixels set on the interpolation line in the previous one-line process, and each of conversion errors of a plurality of first previous-line error using pixels that are at least part of the plurality of first error-using pixels. A first average error calculation unit that calculates a first average error value that is an average error value of the plurality of first error use pixels based on the values;
The original pixel value of the first target pixel is corrected based on the first average error value calculated by the first average error calculation unit, and the first target pixel is calculated based on the pixel value obtained by the correction. The image processing device according to any one of (21) to (29), which is configured to acquire the converted pixel value.

(31) The first average error calculation unit,
Furthermore, the one or more first pixels which are set to be continuous with the first target pixel on the rear side in the line direction on the target line and are a part of the plurality of first error utilization pixels. (1) The image processing apparatus according to (30), wherein the first average error value is calculated based on each conversion error value of the on-line error utilization pixel.

(32) The first average error calculation unit,
The conversion error value of the corresponding previous line processing pixel that is one pixel that is the second target pixel and that is associated with the first target pixel in one unit process in the previous one line process, The image processing according to (30) or (31), wherein the first average error value is calculated using the conversion error value of one of the pixels on the first front-line error utilization pixel. apparatus.

  The mode described in the above three items is a mode in which the same process as the average error calculation process for the second target pixel described above is applied to the unit process for the first target pixel. is there. Since the explanation of the average error calculation processing described in these three sections has many parts overlapping with the previous explanation, explanation here is omitted.

(33) The second unit processing execution unit further acquires a conversion error value of the second target pixel by the unit processing for the second target pixel.
The image processing apparatus outputs a conversion error value of the second target pixel every time the unit process is executed by the second unit process execution unit, and every time the unit process is executed by the first unit process execution unit, The image processing apparatus according to item (32), wherein a conversion error value of one pixel which is a corresponding previous line processing pixel is input.

  The mode described in this section is a mode in which a limitation on input / output of the conversion error value with respect to the image processing apparatus is added. In the aspect of this section, since the conversion error value from the first unit processing execution unit to the second unit processing execution unit can be transferred inside the apparatus, in that case, the two units In a series of unit processing by the processing execution unit, only one conversion error value is input / output to / from the image processing apparatus, and the input / output processing is simplified and simplified.

(34) The plurality of pixels on the first previous line error use are set as a plurality of pixels that are continuous with each other,
The first unit processing execution unit uses the first previous line foremost error use pixel located in the forefront in the line direction among the plurality of first previous line error use pixels for the conversion error value of the corresponding previous line processing pixel. The image processing apparatus according to (32) or (33), wherein unit processing for the first target pixel is executed using the conversion error value of the first target pixel.

  The mode described in this section is a mode in which a limitation on the positional relationship in the line direction between the first target pixel and the error-use pixel used in the unit processing is added.

(35) The first average error calculation unit
Each of the weighting coefficients that are virtually arranged in the line direction and are set corresponding to each of the plurality of pixels on the first previous line error use and the conversion error value of the pixel on the first previous error use on the first line A plurality of first front-line multiplication units corresponding to the number of the plurality of first front-line error-use pixels on which the multiplication process is performed;
When there is a plurality of first front line multiplication units arranged on the rear side closest to the first front line multiplication unit, the stored value and the plurality of first front lines are provided. The result value of the multiplication process by the one corresponding to itself among the line multipliers is added and stored, and when there is no one arranged on the rear side thereof, the plurality of first front line multiplications A plurality of first front-line addition storage units corresponding to the number of pixels on the first front-line error-use pixel that store the result values of the multiplication processing by the one corresponding to itself. Have
The processing by each of the plurality of first front line addition storage units is configured to be sequentially executed from the processing by the one arranged in front, and among the plurality of first front line addition storage units, The image processing device according to item (34), configured to calculate the first average error value based on a stored value of the previous one.

(36) The first average error calculation unit
Furthermore, the one or more first pixels which are set to be continuous with the first target pixel on the rear side in the line direction on the target line and are a part of the plurality of first error utilization pixels. 1 The first average error value is calculated based on the conversion error value of each of the on-line error utilization pixels.
Each of the weighting coefficients that are virtually arranged in the line direction and are set corresponding to each of the one or more first on-line error use pixels and pixels positioned on the rear side closest to the first target pixel. A number of one or more first line multiplication units corresponding to the number of the one or more first line error utilization pixels that perform the multiplication process with the conversion error value;
When one or more first corresponding line multiplying units are provided corresponding to each of the first and second line multiplying units, and each of them is arranged on the rear side closest to itself, the stored value and the first or more first line multipliers are provided. 1 adds the result value of the multiplication process by the one corresponding to itself among the multiplication units for the line and stores it, and if there is no one arranged behind the line, the one or more first corresponding line The number of one or more first corresponding lines corresponding to the number of the one or more first on-line error utilization pixels that store the result value of the multiplication process by the one corresponding to itself among the line multiplying units. An addition storage unit;
The processing by each of the one or more first addition storage units for the line is configured to be sequentially executed from the processing by the one arranged in front, and further, the one or more first addition storage units for the line The image processing device according to item (35), which is configured to calculate the first average error value based on a stored value of the previous one.

  (37) The first average error calculation unit may store the storage value of the foremost one of the plurality of first previous line addition storage units and the foremost of the one or more first line addition storage units. The image processing apparatus according to item (36), configured to calculate a sum of stored values as a first average error value.

  The modes described in the above three items are various modes in which the characteristic average error value calculation process described above is applied to the unit process for the first target pixel as well as the unit process for the second target pixel. is there. The configuration related to the average error value calculation processing described in the above three terms is the same as the configuration related to the processing described above, and thus the description thereof is omitted here. In addition, the merit by the said process demonstrated previously will be enjoyed by superposition in the aspect of said three term in addition to the merit when it applies to the unit process about a 1st object pixel.

(38) A plurality of pixels, each of which is set in the vicinity of the first target pixel in the matrix of pixels of the converted image and whose conversion error value is used to obtain the converted pixel value of the first target pixel Is defined as a plurality of first error-utilizing pixels, each of which is set in the vicinity of the second target pixel in the matrix of pixels of the converted image and acquires its converted pixel value of the second target pixel. In the case where a plurality of pixels for which conversion error values are used are defined as a plurality of second error use pixels,
The first unit processing execution unit includes a first average error calculation unit that calculates a first average error value that is an average error value of the plurality of first error use pixels,
Any of the items (21) to (37), wherein the second unit processing execution unit includes a second average error calculation unit that calculates a second average error value that is an average error value of the plurality of second error use pixels. An image processing apparatus according to claim 1.

  The mode described in this section is a mode in which the first average error calculation unit and the second average error calculation unit listed above are provided in the first unit process execution unit and the second unit process execution unit, respectively.

(39) The image processing apparatus
The original pixel value of the first target pixel is corrected based on the first average error value calculated by the first average error calculation unit, and the first target pixel is determined based on the pixel value obtained by the correction. And the pixel value of the second target pixel is corrected based on the second average error value calculated by the second average error calculation unit, and the pixel value obtained by the correction is determined. The image processing apparatus according to (38), further comprising a single converted pixel value determining unit that determines a converted pixel value of the second target pixel based on the first converted pixel value.

(40) The image processing apparatus is
The pixel value obtained by correcting the original pixel value of the first target pixel based on the first average error value calculated by the first average error calculation unit, and the first obtained based on the pixel value Based on the converted pixel value of the target pixel, a conversion error value of the first target pixel is calculated, and the second target pixel based on the second average error value calculated by the second average error calculation unit Single conversion error value of the second target pixel is calculated based on the pixel value obtained by correcting the pixel value and the converted pixel value of the second target pixel acquired based on the pixel value. The image processing apparatus according to (37) or (38), comprising the conversion error value calculation unit.

  In the aspect described in the above two items, when the first average error calculation unit and the second average error calculation unit are provided in the first unit process execution unit and the second unit process execution unit, respectively, This is a mode in which the conversion pixel value determination unit and the conversion pixel value calculation unit that the unit processing execution unit should have are shared. The modes of the above two terms are particularly effective when the image processing apparatus is mainly composed of an electronic circuit and an electric circuit. That is, even in an image processing apparatus including two unit processing units, the circuit portion corresponding to the conversion pixel value determination unit and the conversion pixel value calculation unit can be made one, thereby simplifying the circuit configuration. It can be done. In addition, about the process of a conversion pixel value determination part and a conversion pixel value calculation part, the various process employ | adopted conventionally can be employ | adopted, Since the process is already well-known, about those processes Description is omitted.

(51) Image data of a source image composed of a plurality of pixels defined as a certain matrix is interpolated by pixel lines by processing according to the error diffusion method while supplementing pixels between the matrix lines. An image processing method for converting into image data of a converted image composed of a plurality of pixels defined as another matrix,
The pixel value of each of the plurality of pixels of the image constituting the image data of the original image, the pixel value of each of the plurality of pixels of the image constituting the image data of the original image and the converted image A value corresponding to a converted pixel value and a line of pixels in a matrix of pixels of the source image, which is also located in the matrix of pixels of the converted image, corresponding to the source line and the source line Then, when defining a line of pixels for interpolating a matrix of pixels of the original image, an interpolation line, and a process for one pixel according to the error diffusion method, a unit process, respectively,
By executing unit processing on the first target pixel that is one pixel existing on the target line that is one of the source lines, the first target pixel is based on the source pixel value of the first target pixel. Get the conversion pixel value and conversion error value of
The original pixel value of the first target pixel before this time, which is set as the first target pixel in one unit processing executed before this time by the first unit processing execution unit, on the interpolation line corresponding to the target line, While using the conversion error value of the first target pixel acquired by the first unit processing execution unit based on the pixel value as the pixel value of the second target pixel associated with the first target pixel, By executing the unit process for the second target pixel, the conversion pixel value of the second target pixel is acquired,
The unit processing for the first target pixel and the unit processing for the second target pixel are respectively performed as the target line while sequentially transitioning the first target pixel and the second target pixel forward in the line direction. An image processing method for converting image data of the original image into image data of the converted image by repeating the interpolation line and repeating the repetition while sequentially changing the target line.

  The aspect described in this section is an aspect of the claimable invention when the category is an image processing method. Since the description of the aspect of this section overlaps with the above aspect belonging to the category of the image processing apparatus, description thereof is omitted here. In addition, although illustration of a specific configuration is omitted in consideration of the redundant specification, the image processing method of the claimable invention has the technical features of the above aspects relating to the image processing apparatus as the aspect of this section. It can be set as the aspect of the various structures applied.

  Hereinafter, an embodiment of the claimable invention and a modification thereof will be described in detail with reference to the drawings, taking an image processing apparatus constituted by an electronic circuit as an example. In addition to the following examples, the claimable invention is implemented in various modes including various modifications and improvements based on the knowledge of those skilled in the art, including the mode described in the above [Mode of Invention]. can do.

≪Overview of image processing≫
As shown in FIG. 1A, the original image to be converted by the image processing apparatus according to the present embodiment has the number of pixels in the column direction (number of lines) as M and the number of pixels in the line direction (number of columns) as N. Is defined as a matrix. Lines, columns, and pixels are generally referred to as m lines and n columns, and pixels are represented as [m, n] corresponding to m lines and n columns, and pixel values, that is, primitive pixel values are , X, or X [m, n] in association with the pixel position. The original pixel value X is a discrete gradation value in increments of 0 to 255. The image data of the source image is configured as a set of source pixel values X [m, n].

  On the other hand, as shown in FIG. 1C, the converted image after conversion is defined as a matrix having 2M pixels in the column direction and N pixels in the line direction. That is, the converted image matrix has twice the number of lines as the original image, and the converted image is obtained by interpolating between the original lines, which are lines existing in the original pixels, by one interpolation line. If the lines of the converted image are generalized to be called 2m-1 line and 2m line, 2m-1 line is the original line, and 2m line is supplemented corresponding to 2m-1. Interpolation line. In the figure, the mark ■ is attached to the original line, and the mark □ is attached to the interpolation line. The column is referred to as n columns as in the original image, and the pixel is expressed as [2m-1, n] on the original line and [2m, n] on the interpolation line, and the pixel value, The converted pixel value is referred to as Z or a pixel on the primitive line in association with the pixel, Z [2m-1, n], and a pixel on the interpolation line as Z [2m, n]. To do. The converted pixel value Z is a binarized value of 0 and 1. The image data of the converted image is configured as a set of converted pixel values Z [2m-1, n], Z [2m, n].

  The conversion from the original image data to the converted image data by a process according to an error diffusion method (hereinafter sometimes referred to as “error diffusion process”) has conventionally been performed by temporarily converting the original image data as shown in FIG. The image data of the original interpolation original image is created, and error diffusion processing is executed on the image data. The interpolation original image data is simply image data of an image in which interpolation lines are supplemented between the original lines. More specifically, each of the primitive pixel values X on the 2m line is created so as to be the pixel value of the same column on the 2m-1 line. Therefore, [2m−1, n] and [2m, n] are configured as a set of primitive pixel values having the same value.

  In the image processing by the image processing apparatus according to the present embodiment (hereinafter sometimes referred to as “image processing according to the present embodiment”), the converted original image data is not generated, and the converted image is directly generated from the original image data. Converted to data. That is, the interpolation of the image by the line of pixels and the conversion process of the original pixel value to the converted image value according to the error diffusion method are executed as a unit. Hereinafter, the image processing of this embodiment will be described with reference to the table shown in FIG.

  The arrangement of pixels in FIG. 2 shows a matrix of converted images. The 2m-1 line shown in the middle row is a primitive line corresponding to the m line of the original image, and the 2m line shown in the lower row corresponds to the 2m-1 line and the m line of the original image. It is a line supplemented between the m + 1 line. The upper line is a line that has been interpolated corresponding to the m−1 line of the original image and has already obtained the converted pixel value Z. In addition, (circle) in a figure has shown that the conversion pixel value Z is already acquired in the pixel.

  In the image processing of the present embodiment, a unit line (first unit processing) is performed on one pixel on the target line with one line of the source line as a target line, more specifically, the source pixel value of the pixel is converted. One set of processing that mainly includes conversion into pixel values and unit processing (second unit processing) for one pixel on the interpolation line corresponding to the target line are executed. That is, a first unit process for a first target pixel that is a pixel that is a pixel value conversion target on the target line, and a second unit process for a second target pixel that is a pixel value conversion target on the interpolation line; Is executed, the converted pixel value Z of the two pixels of the converted image is acquired for the original pixel value X of one pixel of the original image, and these are output. Note that the first target pixel and the second target pixel are indicated by asterisks in the figure. The first target pixel and the second target pixel are sequentially shifted in the line direction (the direction along the pixel line, the horizontal direction in the figure) (the white arrow in the figure), while the target line and the interpolation are performed. One line process, which is all unit processes for the line, is executed, and the one line process is sequentially executed for all the original lines while the target line is changed (shaded arrow shown in the figure). Thus, the original image data is converted into converted image data.

  In the following, the 2m-1 line in the figure is the target line, the 2m line is the interpolation line, the pixel [2m-1, n] is the first target pixel, and the pixel [2m, n-2] is the second target pixel. The first unit process and the second unit process in this case will be described.

In the first unit processing in which the pixel [2m−1, n] is the first target pixel, the pixel value X [m, n] (actually, the original pixel value after the filtering process) in the original pixel input to the image processing apparatus. X ′ [m, n], which is a gradation value of 0 to 255 as in the case of the original pixel value X) is the pixel value (first target pixel value) Y _{1 of} the first target pixel. It is, converted image value for the first pixel value Y ₁ Part (first conversion pixel value) Z ₁ is obtained. At the time of acquisition, an average error that is an average value of conversion error values ΔY of pixels that have already been converted to the converted pixel value Z in the vicinity of the first target pixel, that is, error-use pixels corresponding to the first target pixel. value (first average error value) [Delta] Y _{AVE · 1} is used. Specifically, by adding the first target pixel value Y ₁ and the first average error value ΔY _{AVE · 1} , the corrected target pixel value (the first corrected target value) in which the first target pixel value Y ₁ is corrected. Pixel value) Y ₁ ′ is obtained, the first corrected target pixel value Y ₁ ′ is compared with the binarization threshold S, and the corrected target pixel value Y ₁ ′ is greater than the binarization threshold S The first conversion pixel value Z ₁ is determined to be 1, and when the corrected target pixel value Y ₁ ′ is equal to or less than the binarization threshold S, the first conversion pixel value Z ₁ is determined to be 0. The first converted pixel value Z ₁ determined in this way is output as the converted pixel value Z [2m−1, n] in the converted image.

In order to calculate the first average error value ΔY _{AVE · 1} , an error use pixel (first error use pixel) is set for the first target pixel in a range surrounded by a solid line in the drawing. More specifically, the 2m-1 line that is the target line is the relevant line (first relevant line), and the 2 (m-1) line that is the interpolation line in the previous one-line process is the previous line (first previous line). In this case, five pixels [2 (m−1), n−2] to [2 (m−) that are continuously located on the first previous line around the same n columns as the column of the first target pixel. 1), n + 2] are located on the rear side in the line direction of the first target pixel on the first relevant line as the previous line error utilization pixel (the first previous line error utilization pixel) and are continuous therewith. The two pixels [2m−1, n−2] and [2m−1, n−1] to be set are respectively set as the on-line error use pixel (first on-line error use pixel). . Incidentally, as shown in FIG. 3, a weighting coefficient K corresponding to the relative position with respect to the target pixel is set for each error utilization pixel. Specifically, for example, for the previous line error utilization pixels, Ka = 1/16, Kb = 1/16, Kc = 4/16, Kd = from the rear to the front in the line direction, respectively. A coefficient having a value of 1/16, Ke = 1/16 is Kf = 4/16, Kg = 4/16 for the line error utilization pixels from the rear to the front in the line direction. Coefficients are set (Ka = 1/16, Kb = 2/16, Kc = 4/16, Kd = 2/16, Ke = 1/16, Kf = 2/16, Kg = 4/16 It is also possible to adopt a value or the like), and the weighted coefficient K and the conversion error value ΔY of each of the first error-utilizing pixels are multiplied to obtain a sum of the multiplied values. 1 average error value [Delta] Y _{AVE · 1} is calculated The first average error value ΔY _{AVE · 1} calculated in this way is used in the determination of the first conversion pixel value Z ₁ described above. In the image processing of the present embodiment, as will be described in detail later, in calculating the first average error value ΔY _{AVE · 1} , the front line that is the foremost pixel in the line direction among the first previous line error use pixels. The uppermost error use pixel (the first error use pixel on the first front line: expressed as “first foremost pixel” in the drawing) is set as the second target pixel in one unit process in the previous one line process. The pixel is a pixel associated with the first target pixel (corresponding previous line processing pixel), and the pixel conversion error value ΔY, that is, the pixel [2 (m -1), n + 2], only the conversion error value ΔY [2 (m−1), n + 2] is externally input to the image processing apparatus (hereinafter, this conversion error value is referred to as “input conversion error value ΔY ₀ ”). Conversion error of other error utilizing pixels The difference value ΔY is not input from the outside in the current unit processing.

Further, in the first unit process, the first post-correction pixel value Y ₁ 'and on the basis of the first conversion pixel value Z _1, the conversion error value for the first pixel (first conversion error value) [Delta] Y ₁ Also get. Specifically, when the converted pixel value Z ₁ is 1, a value obtained by subtracting an upper limit pixel value Y _MAX (for example, some value of 255 or less) from the first corrected target pixel value Y ₁ ′. When the converted pixel value Z ₁ is 0, the value obtained by subtracting the lower limit pixel value Y _MIN (for example, 0) from the first corrected target pixel value Y ₁ ′ is the first conversion error value ΔY ₁ , respectively. It is said.

In the second unit processing in which the pixel [2m, n−2] on the interpolation line is the second target pixel, for the reason described later, the source pixel value X ′ [m, n] input in the previous unit processing is That is, the original pixel value of the first target pixel in the first unit processing of the last time is set as the pixel value (second target pixel value) Y _{2 of} the second target pixel, and the converted image for the second target pixel value Y ₂ A value (second converted pixel value) Z ₂ is acquired. In the acquisition, as in the case of the first target pixel, the average error value (second average error value) ΔY _{AVE · 2 of} the error use pixel corresponding to the second target pixel is used to obtain the second target pixel value Y _2. And the second average error value ΔY _{AVE · 2} are added to obtain a corrected target pixel value (second corrected target pixel value) Y ₂ ′ in which the second target pixel value Y ₂ is corrected. The second corrected target pixel value Y ₂ ′ and the binarization threshold value S are compared to determine the second converted pixel value Z ₁ . The second converted pixel value Z ₂ determined in this way is output as the converted pixel value Z [2m, n−2] in the converted image.

An error use pixel (second error use pixel) for calculating the second average error value ΔY _{AVE · 1} is the first error use pixel of the second target pixel in a range surrounded by a broken line in the figure. The positional relationship is set to be equal to the positional relationship with respect to one target pixel. Specifically, when the 2m line that is an interpolation line is the relevant line (second relevant line) and the 2m-1 line that is the target line is the previous line (second previous line), , Pixels [2m−1, n−4] to [2m−1, n] are second pixels on the previous line as error utilization pixels (second previous line error utilization pixels) and on the second line. Two pixels [2m, n-4] and [2m, n-3] that are located on the rear side in the line direction of the target pixel and are continuous therewith are the on-line error use pixel (second on-line error use pixel). ) Will be set respectively. Further, the weighting coefficient K for each of the error utilization pixels is set as shown in FIG. 3 as in the first unit process, and the second average is obtained by the same process as in the first unit process. An error value ΔY _{AVE · 2} is calculated.

In the second unit processing, among the second previous line error use pixels, the foremost error use pixel on the previous line which is the foremost pixel in the line direction (the second error use pixel on the second previous line: The pixel [2m−1, n] is the first target pixel in the current first unit process. Therefore, the first conversion error value ΔY ₁ obtained by the first unit processing is output from the image processing apparatus as it is, in detail, as the conversion error value ΔY of the foremost error utilization pixel on the second previous line. It is used without being. In the image processing of the present embodiment, the relative positional relationship in the line direction between the first target pixel and the second target pixel is set so that such use is possible, and the second unit processing is changed to the first unit processing. On the other hand, unit processing of pixels delayed by two in the number of columns is performed. Therefore, the primitive pixel value X ′ [m, n] set as the first target pixel value is temporarily not changed until the pixel value is set as the second target pixel value in the image processing apparatus. There is memorized. Also in the second unit process, the conversion error value (second conversion error value) ΔY ₂ for the second target pixel is acquired by the same process as in the first unit process. The acquired second conversion error value ΔY ₂ is output from the image processing apparatus, stored in a memory provided outside the apparatus, and in the one-line process next to the one-line process, the corresponding previous time described above. Used as the pixel value of the line processing pixel.

  Although the outline of the image processing has been described above, the various values used in the above description are distinguished from each other as “first” and “second” corresponding to the first unit processing and the second unit processing. In addition, subscripts 1 and 2 are added to the reference numerals. In the following description, a generic name that does not represent “first” and “second” may be used, and in that case, a subscript may not be added.

<< Configuration of image processing apparatus >>
The image processing apparatus 10 according to the present embodiment is incorporated in a complex machine in which a line scanner and an inkjet printer are combined, and has a configuration as shown in a block diagram in FIG. The primitive image data is obtained by applying a primitive pixel value (specifically, a filter pixel, which is smoothed) to the primitive image data being read by the line scanner by a filter 12 provided outside the image processing apparatus. For each post-processing primitive pixel value) X ′ [m, n], the pixel values are sequentially input to the image processing apparatus 10. This primitive pixel value X ′ [m, n] is treated as the target pixel value Y.

The image processing apparatus 10 includes a correction pixel value determination unit 18 that includes a correction unit 14 and a comparison unit 16 and determines a conversion pixel value Z for the target pixel value Y. The correction unit 14 is configured mainly by an adder. The correction unit 14 adds the target pixel value Y and the average error value ΔY _AVE target pixel value, so that the target pixel value Y becomes the average error value. A corrected target pixel position Y ′ corrected by ΔY _AVE is obtained. The comparison unit 16 is mainly composed of a comparator, and obtains a binarized converted pixel value Z for the target pixel by comparing the corrected target pixel position Y ′ with the binarization threshold S. Has been. Further, the image processing apparatus 10 includes a conversion error value calculation unit 20 that calculates the conversion error value ΔY of the target pixel based on the corrected target pixel value Y ′ and the conversion pixel value Z. Further, in each of the two unit processes described above, there are two average error calculation units for calculating the average error value ΔY _AVE of the error use pixel. More specifically, one of them is a first average error calculation unit 22 that calculates a first average error value ΔY _{AVE · 1} based on an input conversion error value ΔY ₀ from the outside in the first unit processing. The other is a second average error calculation unit 24 that calculates the second average error value ΔY _{AVE · 2} in the second unit process.

  The two average error calculation units will be described in more detail. The first average error calculation unit 22 includes seven multiplication units 26a to 26g each including a multiplier, as shown in a block diagram in FIG. Seven adder storage units 32a to 32g each consisting mainly of registers 28a to 28g and adders 30b to 30e and 30g (addition storage units 32a and 32f are not provided with a register), a final adder 36, It is comprised including.

The multiplication units 26a to 26e and the addition storage units 32a to 32e have a one-to-one correspondence, and they are the five first front lines in the calculation process of the first average error value ΔY _{AVE · 1.} More specifically, each of the error utilization pixels corresponds to each of the first previous line error utilization pixels in the order of their subscripts a to e toward the front in the line direction. Thus, the multiplication units 26a to 26e and the addition storage units 32a to 32e are virtually arranged in the line direction. That is, the upper side in the figure corresponds to the rear in the line direction, and the lower side corresponds to the front in the line direction.

From the above configuration, the multipliers 26a to 26e and the addition storage units 32a to 32e are respectively a previous line multiplication unit (first front line multiplication unit) and a previous line addition storage unit (first front line use). Functions as an addition storage unit). Specifically, the multiplying units 26a to 26e respectively input the conversion error value ΔY ₀ that is the conversion error value of the foremost error use pixel on the first previous line and is input to the image processing apparatus 10 and the weighting coefficients Ka to Ke. Multiplication processing with each of the above is performed. In addition, the addition storage units 32b to 32e and the result values of the multiplication processes of the multiplication units 26b to 26e corresponding to the addition storage units 32b to 32e and the registers 28a to 32d of the addition storage units 32a to 32d on the latest rear side (upper side in the figure) of itself. The stored value stored in 28d is added by its own adders 30b to 30e, and the added value is stored in its own register 28b to 28e. The addition storage unit 32a corresponds to itself. The result value of the multiplication process of the multiplying unit 26a is stored in its own registers 28b to 28e.

Similarly, the multiplication units 26f and 26g and the addition storage units 32f and 32e correspond to each other on a one-to-one basis, and they correspond to the two _first processes in the calculation process of the first average error value ΔY _{AVE · 1} . More specifically, each of the one line error using pixels corresponds to each of the first line error using pixels in the order of the subscripts f and g in the forward direction in the line direction. As a result, the multiplication units 26f and 26g and the addition storage units 32f and 32g are virtually arranged in the line direction, like the multiplication units 26a to 26e and the addition storage units 32a to 32e. That is, the upper side in the figure corresponds to the rear in the line direction, and the lower side corresponds to the front in the line direction.

With the above-described configuration, the multiplication units 26f and 26g and the addition storage units 32f and 32g respectively include the line multiplication unit (first corresponding line multiplication unit) and the line addition storage unit (first corresponding line use). Functions as an addition storage unit). In detail, the multiplication unit 26f, 26 g, respectively, the first conversion error value [Delta] Y ₁ is a conversion error value of the first target pixel of the current calculated by the conversion error value computing section 20, the first the line of The conversion error value ΔY of the pixel immediately behind the first target pixel in the next first unit process is multiplied by each of the weighting coefficients Kf and Kg. Further, the addition storage unit 32g has a result value of the multiplication process of the multiplication unit 26g corresponding to itself, and a storage value stored in the register 28f of the addition storage unit 32g on the latest rear side (upper side in the figure) of itself. Is added by its own adder 30g, and the addition value is stored in its own register 28g, and the addition storage unit 32f obtains the result value of the multiplication process of the multiplication unit 26f corresponding to itself. It is stored in its own register 28f.

The first average error calculation unit 22 is configured such that the value of the register 28e of the addition storage unit 32e and the value of the register 28g of the addition storage unit 32g are added by the final adder 36. The addition storage units 32a to 32e and the addition storage units 32f and 32g are sequentially executed from the processing by the one arranged forward. In other words, the processing is sequentially performed from the lower position to the upper position in the figure. More specifically, the processing of the first average error calculation unit 22 is performed by first executing processing by the multiplication unit 26e and the addition storage unit 32e, and subsequent addition processing by the final adder 36. A first average error value ΔY _{AVE · 1} of the first error utilization pixel with respect to the target pixel is calculated, and then processing by the multiplication units 26a to 26d and the addition storage units 32a to 32d and multiplication units 26f and 26g, and an addition storage unit 32f , 32g are performed in order from the one located on the front side. Therefore, processing after the first average error value [Delta] Y _{AVE · 1} is calculated, it is executed as a preparation process for the first average error value [Delta] Y _{AVE · 1} calculated in the first unit processing the next round become.

  As shown in the block diagram of FIG. 6, the second average error calculation unit 24 includes seven multiplication units 38a to 38g each of which mainly includes a multiplier, and registers 40a to 40g and adders 42b to 42e and 42g, respectively. And 7 addition storage units 44a to 44g (addition storage units 44a and 44f are not provided with a register) and a final adder 48.

Since the above configuration is the same as that of the first average error calculation unit 22, simply explaining, the multiplication units 38 a to 38 e and the addition storage units 44 a to 44 e each have a second average error value ΔY _{AVE · 2} . Corresponding to each of the five second previous line error utilization pixels in the calculation process, as a previous line multiplication unit (second previous line multiplication unit) and a previous line addition storage unit (second previous line addition storage unit) Function. Further, the multiplication units 38f and 38g and the addition storage units 44f and 44g correspond to each of the two second line error utilization pixels, respectively, the line multiplication unit (second line multiplication unit), and the line It functions as an addition storage unit (second addition storage unit for the line). Note that, in the second average error value calculation unit 24, the multiplication units 38a to 38e are first conversion error values of the first target pixel calculated in the current first unit process calculated by the conversion error value calculation unit 20, respectively. The conversion error value ΔY ₁ is used as the conversion error value of the foremost error utilization pixel on the second previous line, and multiplication processing is performed on each of the weighting coefficients Ka to Ke. Further, multiplying unit 38f, 38 g, respectively, the second conversion error value [Delta] Y ₂ is a conversion error value of the second target pixel of the current calculated by the conversion error value computing section 20, the second the lines of the next As the conversion error value ΔY of the pixel immediately behind the second target pixel in the second unit process, a multiplication process is performed on the conversion error value ΔY and each of the weighting coefficients Kf and Kg. Then, processing is performed in the same order as the first conversion error calculation unit 24, and the second average error value ΔY _{AVE · 2} of the second error utilization pixel for the current second target pixel is calculated, and the second time of the next round. Preparation processing for calculating the second average error value ΔY _{AVE · 2} in the unit processing is performed.

Here, the conversion error value storage memory 50 provided outside the image processing apparatus 10 is a line memory having a storage area substantially corresponding to the number of pixels on one line, as shown in FIG. (Actually, depending on the positional relationship between the first target pixel and the second target pixel in the line direction, two extra pixels are provided in the front and rear in the line direction), .., ΔY (n−1), ΔY (n), ΔY (n + 1),... Corresponding to the columns are stored in the respective areas. Each time the second unit process is executed, the second conversion error value ΔY ₂ is stored in the storage area corresponding to the column of the second target pixel, and is associated with the first target pixel for each first unit process. The corresponding previous line process pixel, that is, the storage area corresponding to the column of the foremost error utilization pixel on the first previous line is read out. This conversion error value storage memory 50 may be provided in the image processing apparatus 10, and if configured in this manner, the pixel value input / output processing between the image processing apparatus 10 and the outside is further simplified. Is possible.

In addition, the image processing apparatus 10 includes a primitive pixel value temporary storage unit 52. As shown in FIG. 2, the temporary storage unit 52 is mainly configured by a first-in first-out register having three storage areas FIFO (0) to FIFO (-2). The storage value of the storage area is stored in the storage area. FIFO (0) to FIFO (-2) can be moved sequentially. With such a configuration, the primitive pixel value X ′ [m, n] input to the primitive pixel value temporary storage unit 52 in the current unit process is used as the second target pixel value Y ₂ in the subsequent unit process. The

  With the configuration as described above, the image processing apparatus 10 includes the first unit processing execution unit 54 that includes the conversion pixel value determination unit 18, the conversion error value determination unit 20, and the first average error calculation unit 22. A second unit processing execution unit 56 including a conversion pixel value determination unit 18, a conversion error value determination unit 20, and a second average error calculation unit 24 is provided. That is, the conversion pixel value determination unit 18 and the conversion error value determination unit 20 are function units shared by the first unit processing execution unit 54 and the second unit processing execution unit 56, and a part of the processing in the first unit processing. And some processes in the second unit process are alternately performed.

≪Image processing flow≫
FIG. 7 shows a flowchart of the above-described image processing by the image processing apparatus 10. Below, based on the flowchart, the flow of this image processing is demonstrated along with progress of time. Since the image processing apparatus 10 is configured mainly with an electronic circuit, two or more processes are executed in parallel. Actually, the image processing process of the image processing apparatus 10 has a strict meaning. However, it does not follow this flowchart. The processing flow described here is merely a guideline for facilitating understanding of the image processing.

In this image processing, first, in step 1 (hereinafter abbreviated as “S1”, the same applies to other steps), the value of m that functions as a line counter is reset to 1. Subsequently, in S2, the value of n functioning as a column counter is reset to 1, and each value of the storage areas FIFO (0) to FIFO (−2) of the original pixel value temporary storage unit 52, the first average error calculator 22 register values R _A1 to R _G1 registers 28a~28g having register value R _A2 to R _G2 registers 40a~40g the second average error calculation unit 24 has is reset to 0, respectively. In the conversion error value storage memory 50, all storage areas are reset to 0 when the main image processing is started.

Next, in S <b> 3, the original pixel value X ′ [m, n] after the filtering process of the original image is input to the image processing apparatus 10. Subsequently, the source pixel value X ′ [m, n] is recognized as the first target pixel value Y ₁ in S4, and is stored in the storage area FIFO (0) of the source pixel value temporary storage unit 52 in S5. The Next, in S6, the storage value [Delta] Y of the storage area corresponding to the n + 2 columns of the conversion error value storage memory 50 (n + 2) is, as the input conversion error value [Delta] Y _0, is input.

Next, in S7, the first unit process shown in the flowchart of FIG. 8 is executed. In the first unit processing, first, in S31, the multiplication unit 26e, multiplied by the input conversion error value [Delta] Y ₀ and the weighting coefficient Ke is, the stored value of the multiplied what was the register 28d is, in addition storage unit 32e The value is added by the adder 30e, and the added value becomes the register value R _E1 of the register 28e. In subsequent S32, the register value R _E1 of the register 28e and the register value R _G1 of the register 28g are added by the final adder 36 to calculate the first average error value ΔY _{AVE · 1} . Next, in S33 to S35, the input conversion error value ΔY ₀ and each of the weighting coefficients Kd to Kb are multiplied by the multiplication units 26d to 26b in order from the front side (from the lower side in the figure), The multiplied value and each of the stored values of the registers 28c to 28a are added by the adders 30d to 30b of the adding storage units 32d to 32b, and each of the added values is the register value R _{D1 of the} registers 28d to 28b. ˜R _B1 . Then, in S36, the multiplication unit 26a, multiplied by the input conversion error value [Delta] Y ₀ and the weighting coefficient Ka is, those that multiplied is the register value R _A1 of the register 28a. The processes of S31 to S36 are performed by the first conversion error calculation unit 22 (in the flowchart, steps surrounded by a broken line are steps performed by the first conversion error calculation unit 22).

Next, in S37, the first corrected target pixel value Y _{1 obtained} by correcting the first target pixel value Y ₁ by adding the first target pixel value Y ₁ and the first average error value ΔY _{AVE · 1.} 'Is acquired. This process is performed by the correction unit 14. Then, in S38, after the first correction target pixel value Y ₁ 'is or not larger than the binarization threshold value S or not. If it is larger than the binarization threshold S, the first conversion pixel value Z ₁ is determined to be 1 in S39, and if it is less than or equal to the binarization threshold S, the first conversion pixel value Z ₁ is 0 in S40. To be determined. The processing of S38 to S40 is performed by the comparison unit 16, and the processing of S37 to S40 is performed by the conversion pixel value determination unit 18. If the first conversion pixel value Z ₁ is determined to be 1, the above-described upper limit pixel value Y _MAX is subtracted from the first corrected target pixel value Y ₁ ′ in S41, and the first conversion pixel value Z _{1 is determined.} Is determined to be 0, in S42, the first lower limit pixel value Y _MIN is subtracted from the first corrected target pixel value Y ₁ ′ to calculate the first conversion error value ΔY ₁ . The processes of S41 and S42 are executed by the conversion error value calculation unit 20.

Next, in S43, the multiplying unit 26 g, is first converted error value [Delta] Y ₁ calculated weighting coefficient Kg is multiplied, and the stored value of the multiplied what was the register 28f is, addition of adding storage unit 44g The value is added by the device 42g, and the added value is used as the register value R _G1 of the register 28g. Then, in S44, the multiplication unit 26f, are first converted error value [Delta] Y ₁ and the weighting coefficient Kf is multiplied, those that multiplied is the register value R _F1 register 28f. The processes of S43 and S44 are performed by the first conversion error calculation unit 22, the processes are completed, and the first unit process is completed.

After the first unit process S7, in S8, the first converted pixel value Z ₁ is determined, pixels on source lines in the converted image [2m-1, n] of the converted pixel value Z [2m-1, n ] Is output. Next, in S9, the original pixel value temporary storage unit 52 is updated. Specifically, the value of the storage area FIFO (−2) is set to the value of FIFO (−1), and then the value of FIFO (−1) is set to the value of FIFO (0). Then, in S10, the value of the storage area FIFO (-2) is the second target pixel value Y _2. After the process of S10, in S11, the second unit process shown in the flowchart of FIG. 9 is executed.

Since each of S51 to S64 in the second unit process is substantially the same as each of S31 to S44 in the first unit process, only a simple description thereof will be given. The difference is that the process performed in the first average error calculation unit 22 in the first unit process (the process surrounded by a broken line) is performed by the second average error calculation unit 24, and the input conversion is performed in the process. Instead of the error value ΔY ₀ , the first conversion error value ΔY ₁ calculated in the first unit process is multiplied by the weighting coefficients Ka to Kg by the multipliers 38 a to 38 g, respectively. The second average error value ΔY _{AVE · 2} is calculated by the process of the second average error calculation unit 24 in the second unit process, and in the second unit process, based on the second average error value ΔY _{AVE · 2} , The second conversion pixel value Z ₂ is determined, and the second conversion error value ΔY ₂ is calculated.

After the second unit processing, in S12, the second converted pixel value Z ₂ is determined, the pixel [2m, n-2] on the interpolation line in the converted image converted pixel value Z [2m, n-2] as In S13, the calculated second conversion error value ΔY ₂ is stored in the storage area corresponding to the column of the second target pixel in the conversion error value storage memory 50 in the storage area Y ( n-2).

  Next, in S14, the value of n is counted up, and in subsequent S15, it is determined whether or not the value of n is larger than the value obtained by adding 2 to the total number N of columns of the original image. If the value is equal to or less than the value, the processes after S3 are repeated. If it is greater than that value, it is assumed that the one-line process has been completed, and the value of m is counted up in S16, and the process proceeds to the one-line process for the next target line. Then, in S17, it is determined whether or not the value of m is larger than the total column number N of the original image. If it is less than or equal to N, the process from S2 is repeated. As a result of completion of the line processing, the image processing ends.

  In the above processing, there is a second unit processing when n is 0 or less, and a first unit processing when n is larger than N. Since these processes are processes for the second target pixel and the first target pixel that protrude from the matrix of the original image, they are performed in a dummy manner.

  In addition, the image processing described above is image processing configured by an electronic circuit. However, when the image processing is performed by an image processing apparatus mainly including a computer, a program according to the flowchart is created, and the program is It can be executed by a computer. In this case, each functional unit that has an entity in the image processing apparatus 10 becomes a virtual or conceptual functional unit that executes the processing performed by the functional unit.

≪Modification≫
Hereinafter, a modified example in which the processing order in the first average error calculation unit 22 and the second average error calculation unit 24 is changed will be described. Note that the image processing apparatus according to the modified example is also referred to as the image processing apparatus 10, and the same reference numerals are used for the functional units included in the image processing apparatus.

In the first average error calculation unit 22 and the second average error calculation unit 24 in the image processing apparatus 10 according to the modification, the average error value calculation processing is performed in the order shown in the flowcharts of FIGS. Specifically, only S31 and S32 in FIG. 8 are replaced with S51 and S52 in FIG. 5 and 6, first, after the addition processing by the final adders 36 and 48 is executed, the processing by the multiplication units 38 and 40 and the addition storage units 32 and 44 is performed forward in the line direction. It is performed sequentially from the one on the side (the one located below in the figure). When the processes are executed in this order, the calculated first average error value ΔY _{AVE · 1} and second average error value ΔY _{AVE · 2} are the first target pixel and the second target pixel in the current unit processing. Of the first error utilization pixel and the second error utilization pixel with respect to the input conversion error value ΔY ₀ input to the first average error calculation unit 22 and the first conversion input to the second average error calculation unit 24. The error value ΔY ₁ becomes the conversion error value ΔY of the foremost error using pixel on the first previous line and the foremost error using pixel on the second previous line corresponding to the first target pixel and the second target pixel in the next unit processing. That is, the processing by each of the multiplication units 38 and 40 and the addition storage units 32 and 44 calculates the first average error value ΔY _{AVE · 1} and the second average error value ΔY _{AVE · 2} in the next unit processing. Preparation process.

From the above, in this image processing, when the first target pixel is [2m−1, n], as shown in FIG. 10, the input conversion error value ΔY ₀ input from the conversion error value storage memory 50 is shown. Are stored in a storage area corresponding to the foremost error use pixel on the first previous line (represented as “next first foremost pixel” in the drawing) for the first target pixel in the next first unit process. Stored value ΔY (n + 3). In addition, the conversion error value ΔY ₁ calculated in the first unit process of this time is the first error use pixel on the second previous line for the second target pixel in the next second unit process (in the figure, “next second forefront next time”). The second target image pixel is three pixels behind in the line direction with respect to the first target pixel.

Due to the positional relationship between the first target pixel and the second target pixel, the second conversion error value ΔY ₂ calculated by the second unit process corresponds to a column of the second target pixel in the conversion error value storage memory 50. The storage value ΔY (n−3) to be stored in the storage area of the original image value, and the storage area of the original image value temporary storage unit 52 is expanded by one from FIFO (0) to FIFO (3). . In the image processing of this modification, two converted pixel values Z [2m−1, n] and Z [2m, n−3] are obtained by unit processing for one primitive pixel value X ′ [m, n]. Will be obtained. The main flow of this image processing is as shown in FIG. 11 due to the difference from the image processing described above. Since this flow is substantially the same as the previous flow, description thereof is omitted here. The overall configuration of the image processing apparatus 10 is the same as that shown in FIG.

3 is a conceptual table showing image data of a source image that is a target of an image processing apparatus according to an embodiment and image data of a converted image obtained by executing image processing by the image processing apparatus. 3 is a conceptual table used for explaining image processing executed by the image processing apparatus according to the embodiment. It is a conceptual table which shows the weighting coefficient set in the image processing by the image processing apparatus of an Example. It is a block diagram which shows the structure of the image processing apparatus of an Example. It is a block diagram which shows the 1st average error value calculation part which the image processing apparatus of an Example has. It is a block diagram which shows the 2nd average error value calculation part which the image processing apparatus of an Example has. 6 is a flowchart illustrating a flow of image processing executed by the image processing apparatus according to the embodiment. It is a flowchart which shows the flow of the 1st unit process performed by the image processing apparatus of an Example. It is a flowchart which shows the flow of the 2nd unit process performed by the image processing apparatus of an Example. It is a conceptual table used in order to explain the image processing performed by the phase processing apparatus of the modification. It is a flowchart which shows the flow of the image processing performed by the image processing apparatus of a modification. It is a flowchart which shows the flow of the 1st unit process performed by the image processing apparatus of a modification. It is a flowchart which shows the flow of the 2nd unit process performed by the image processing apparatus of a modification.

Explanation of symbols

10: Image processing device 12: Filter 14: Correction unit 16: Comparison unit 18: Conversion pixel value determination unit 20: Conversion error value calculation unit 22: First average error calculation unit 24: Second average error calculation units 26a to 26g: Multipliers 28a to 28g: Registers 30b to 30e, 30g: Adders 32a to 32g: Addition storage units 36: Final adders 38a to 38g: Multipliers 40a to 40g: Registers 42b to 42e, 42g: Adders 44a to 44g: Addition storage unit 48: final adder 50: conversion error value storage memory 52: primitive pixel value temporary storage unit 54: first unit processing execution unit 56: second unit processing execution unit

Claims (5)

An image processing apparatus used for converting image data of a source image composed of a plurality of pixels defined as a certain matrix into image data of a converted image by processing according to an error diffusion method,
The image processing apparatus is
The pixel value of each of the plurality of pixels of the image constituting the image data of the original image, the pixel value of each of the plurality of pixels of the image constituting the image data of the original image and the converted image When the value is defined as a converted pixel value and a process for one pixel according to the error diffusion method as a unit process,
Unit processing is performed on a target pixel that is one pixel existing on a target line that is one of the pixel lines in the matrix, and the converted pixel value of the target pixel is based on the source pixel value of the target pixel. And a unit processing execution unit for obtaining a conversion error value,
While the target pixel is sequentially shifted toward the front in the line direction, one-line processing in which unit processing by the unit processing execution unit is repeated for the target line is executed, and the target line is sequentially shifted. The image data of the original image is converted into the image data of the converted image by repeating the one-line process while being
The unit processing execution unit
In the case where a plurality of pixels, each of which is set in the vicinity of the target pixel in the matrix and whose conversion error value is used to obtain a conversion pixel value of the target pixel, are defined as a plurality of error use pixels. ,
Conversion of each of a plurality of pixels on the previous line that are a plurality of pixels set to be continuous with each other on the target line in the previous one-line process and are at least part of the plurality of pixels using the error An average error calculation unit that calculates an average error value of the plurality of error use pixels based on an error value;
The original pixel value of the target pixel is corrected based on the average error value calculated by the average error calculation unit, and the converted pixel value of the target pixel is acquired based on the pixel value obtained by the correction. Composed of
The average error calculator is
In the case where the foremost error use pixel on the previous line is defined as the foremost error use pixel on the previous line among the plurality of previous line error use pixels,
Virtually arranged in the line direction, and executes a multiplication process of each of the weighting coefficients set corresponding to each of the plurality of previous line error use pixels and the conversion error value of the foremost error use pixel on the previous line. A plurality of front line multipliers corresponding to the number of pixels on the previous line error-use,
When there are those arranged on the rear side nearest to each of the plurality of front line multipliers, the stored value of each and the plurality of front line multipliers are provided. And adding and storing the result value of the multiplication process by the one corresponding to itself, and when there is no one arranged on the rear side of itself, it is stored in the plurality of front line multiplication units. A plurality of previous-line addition storage units corresponding to the number of the previous-line error-use pixels in which the result values of multiplication processing by corresponding ones are stored;
The processing by each of the plurality of previous line addition storage units is configured to be executed sequentially from the processing by the one arranged in front, and the storage of the foremost one of the plurality of previous line addition storage units is stored. An image processing apparatus configured to calculate the average error value based on a value. The average error calculator is
Further, the one or more pixels set to be continuous with the target pixel on the rear side in the line direction on the target line, and one or more on-line error use that is a part of the plurality of error use pixels Based on the conversion error value of each pixel, the average error value is calculated,
Each of the weighting coefficients that are virtually arranged in the line direction and are set corresponding to each of the one or more on-line error use pixels, and the conversion error value of the pixel located immediately behind the target pixel, A number of one or more corresponding line multiplying units corresponding to the number of the one or more on-line error utilizing pixels for executing the multiplication processing of
If there is one that is arranged corresponding to each of the one or more multiplication units for the line, and each of them is arranged in the immediate rear side, the stored value and the one or more for the line The result value of the multiplication process by the one corresponding to itself among the multiplication units is added and stored, and when there is no one arranged behind the multiplication unit, one of the one or more corresponding line multiplication units A number of one or more addition storage units for the line corresponding to the number of the on-line error utilization pixels of one or more of which stores the result value of the multiplication process by the one corresponding to itself,
The processing by each of the one or more line addition storage units is configured to be executed sequentially from the processing by the one arranged in front, and the forefront of the one or more line addition storage units. The image processing apparatus according to claim 1, wherein the average error value is calculated on the basis of a stored value.   The average error calculation unit calculates the sum of the stored value of the foremost one of the plurality of previous line addition storage units and the stored value of the foremost one of the one or more line addition storage units, The image processing apparatus according to claim 2, wherein the image processing apparatus is configured to calculate an average error value.   The conversion error value of one pixel that becomes the foremost error use pixel on the previous line is input to the image processing apparatus every time the unit processing is executed by the unit processing execution unit. 4. The image processing device according to any one of 3. The image processing apparatus according to claim 4, wherein the conversion error value of the target pixel is output each time the unit processing execution unit executes the unit processing.

Images