JP3500639B2 - Image forming device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine or a printer which converts read data into reproduced color data to form a multicolor image.

[0002]

2. Description of the Related Art In a printer or the like which reproduces an image in full color, red, green and blue (primary color system) read from an original
Digital image data R, G, B of three colors of cyan for color reproduction,
An image is reproduced by converting it to magenta and yellow C, M, Y (complementary color system) data. Therefore, data processing for converting digital data of three colors of red, green, and blue obtained by scanning the document into data of three reproduced colors for image reproduction is performed.

[0003]

By the way, regarding data processing of full-color images, (a) compatibility of black vividness and color saturation, (b) improvement of color reproducibility, (c) compatibility of resolution and smoothness Must be considered. That is,
(a) In reproducing black in a full-color image, even if cyan C, magenta M, and yellow Y are superimposed to reproduce black, it is difficult to reproduce clear black due to the influence of the spectral characteristics of each toner. Therefore, the reproducibility of black is improved by the subtractive color mixture method using the reproduction color data Y, M, and C and the black printing using the black data K. However, with this method, the sharpness of black improves as the degree of black printing increases, but the saturation of chromatic colors decreases. Therefore, in a full-color image, it is necessary to achieve both improvement in achromatic color sharpness and improvement in chromatic color saturation. (b) Further, masking correction is performed in order to compensate the deviation of the filter characteristics and toner characteristics from the ideal characteristics in color reading, but this masking correction affects the color reproducibility. (c) In addition, the image processing method is changed between an image in which it is better to emphasize edges such as characters and thin lines and a halftone image in which it is better to create smoothness like a photograph, and the edge (brightness is sharp It is better to perform detection and smoothing processing. However, even if edge enhancement is simply performed on a color image, the image density also changes with changes in hue and saturation, and thus such discrimination does not always work well.
For example, when the color changes from white to red, edge enhancement may be used, but when the color changes from red to cyan, the hue changes strangely due to the edge such as the color ghost phenomenon. It is better not to The skin color etc. has a great influence.

Therefore, it is considered that the image reproducibility is improved by changing the data processing method according to the characteristics of the full-color image. Conventionally, data processing has been changed according to the characteristics of the image area. For example, it has been performed to specify an area for processing a character image and an area for processing a halftone image to perform optimal processing for each area. In this case, the user has to specify the area,
Moreover, it is troublesome to specify the image features in detail. Further, there is a color change function for identifying and changing a specific color by a table index using the read data of R, G, B as input parameters. However, although mask processing using a majority decision with respect to the determination result has been performed to prevent erroneous determination of a specific color, the improvement of the effect was actually small.

An object of the present invention is to provide an image forming apparatus having improved reproducibility of full color image.

[0006]

A first image forming apparatus according to the present invention comprises an input means for inputting image data, and a filtering means for performing a two-dimensional spatial digital filtering process on the input image data. , The above filtering
Chromatic area and achromatic area for image data
And a setting unit that sets color correction parameters for performing color correction processing on the input image data based on the image data that has been subjected to the filtering processing , and the setting unit set by the setting unit . It is characterized by further comprising: a correction unit that performs a color correction process on the input image data of the area determined as the chromatic color by the determination unit based on the color correction parameter. A second image forming apparatus according to the present invention includes input means for inputting image data, smoothing means for performing smoothing processing on the input image data,
A chromatic color for the image data that has been smoothed
Discriminating means for discriminating the region and the achromatic region, a setting unit on the basis of the smoothing processing is image data subjected to set the color correction parameters for performing color correction processing on input image data, wherein Based on the color correction parameter set by the setting unit , the determining unit determines that the color is chromatic.
And a correction unit that performs a color correction process on the input image data in the different area . In the first or second image forming apparatus, for example, the color correction process is a masking process and the color correction parameter is a masking coefficient.

[0007]

After the two-dimensional spatial digital filtering process or the smoothing process is performed on the input image data, the image data is processed.
With respect to the chromatic color area and the achromatic color area, the color correction parameter is set and the color correction processing is performed based on the set color correction parameter. Since noise is removed by smoothing processing, the accuracy of image feature determination is improved, and the reproducibility such as color reproducibility is improved.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A digital color copying machine as an embodiment of the present invention will be described below in the following order with reference to the accompanying drawings. (a) Configuration of digital color copying machine (b) Image signal processing (b-1) Configuration of image signal processing unit (b-2) Area determination result and outline of image signal processing (c) Density conversion unit (d) Black generation part (e) Undercolor removal / black addition automatic control in area discrimination part (achromatic color chromatic color determination) (e-1) Purpose of undercolor removal / black addition automatic control (e-2) Smoothing process ( e-3) Achromatic color chromatic color determination (f) Automatic masking control (hue determination) in the area determination unit (f-1) Purpose of automatic masking control (f-2) Hue determination (g) Color correction processing unit (h) Edge enhancement / smoothing automatic control (edge determination) in area discrimination unit (h-1) Purpose of edge enhancement / smoothing automatic control (n-2) Edge detection (i) MTF correction unit

(A) Configuration of Digital Color Copying Machine FIG. 1 is a vertical sectional view showing the overall configuration of a digital color copying machine according to an embodiment of the present invention. The digital color copying machine includes an image reader unit 100 that reads an original image and a main body unit 20 that reproduces the image read by the image reader unit.
It is roughly divided into 0.

In FIG. 1, a scanner 10 comprises an exposure lamp 12 for irradiating a document, a rod lens array 13 for condensing the reflected light from the document, and a contact type CCD for converting the condensed light into an electric signal. A color image sensor 14 is provided. The scanner 10 uses the motor 1 when reading a document.
It is driven by 1 to move in the direction of the arrow (sub-scanning direction) to scan the document placed on the platen 15. The image on the document surface illuminated by the exposure lamp 12 is photoelectrically converted by the image sensor 14. The R, G, B multi-valued electrical signals obtained by the image sensor 14 are processed by the read signal processing unit 20 to be yellow (Y), magenta (M), and cyan.
(C) or black (K) grayscale data. Next, the print head unit 31 corrects the input gradation data according to the gradation characteristic of the photoconductor (γ
(Correction) and, if necessary, dither processing, and then D / A-converts the corrected image data to generate a laser diode drive signal, and the laser diode 221 (see FIG. Drive (not shown).

Laser diode 2 corresponding to gradation data
The laser beam emitted from the laser beam 21 exposes the photosensitive drum 41, which is rotationally driven, via the reflecting mirror 37, as shown by the alternate long and short dash line in FIG. As a result, an image of the original is formed on the photoconductor of the photoconductor drum 41. Photoconductor drum 41
The eraser lamp 42 before receiving the exposure for each copy.
And is charged by the charging charger 43. When exposed in this uniformly charged state, an electrostatic latent image is formed on the photosensitive drum 41. Only one of the yellow, magenta, cyan, and black toner developing devices 45a to 45d is selected to develop the electrostatic latent image on the photosensitive drum 41. The developed image is transferred by the transfer charger 46 onto the copy paper wound around the transfer drum 51.

The above printing process is repeated for yellow, magenta, cyan and black. At this time, the scanner 10 repeats the scanning operation in synchronization with the operations of the photosensitive drum 41 and the transfer drum 51. After that, the copy paper is separated from the transfer drum 51 by operating the separation claw 47, is fixed through the fixing device 48, and is discharged to the discharge tray 49. The copy paper is fed from the paper cassette 50, and its tip is chucked by the chucking mechanism 52 on the transfer drum 51 so that the positional deviation does not occur during transfer.

2 and 3 are block diagrams of the entire control system of the digital color copying machine. Image reader unit 100
Is controlled by the image reader control unit 101. The image reader control unit 101 controls the exposure lamp 12 via the drive I / O 103 according to a position signal from the position detection switch 102 indicating the position of the document on the platen 15, and also controls the drum I / O 103 and the parallel I / O 103. O
The scan motor driver 105 is controlled via 104. The scan motor 11 is a scan motor driver 10
Driven by 5.

On the other hand, the image reader control unit 101 is connected to the image control unit 106 by a bus. Image control unit 1
Reference numeral 06 is connected to each of the CCD color image sensor 14 and the image signal processing unit 20 by a bus. The image signal from the CCD color image sensor 14 is input to the image signal processing unit 20 described later and processed.

The main body section 200 is provided with a printer control section 201 for generally controlling the copying operation and a print head control section 202 for controlling the print head section 31.
Analog signals from various sensors 44, 60, 203 to 205 for automatic density control are input to the printer control unit 201. In addition, a key input to the operation panel 206 causes the printer control unit 2 to operate via the parallel I / O 207.
Various data is input to 01. Printer control unit 201
Is a control ROM 208 in which a control program is stored.
And a data ROM 209 in which various data are stored are connected. The printer control unit 201 includes various sensors 44, 6
0, 203-205, operation panel 206 and data R
The data from the OM 209 controls the copy control unit 210 and the display panel 211 in accordance with the contents of the control ROM 208, and further, in order to perform automatic density compensation control, the grid of the charging charger via the parallel I / O 212 and the drive I / O 213. High voltage unit for voltage generation 214
And controlling the developing device bias voltage generating high voltage unit 215.

The print head controller 202 controls the control RO.
It operates according to the control program stored in the M216, and is connected to the image signal processing unit 20 of the image reader unit 100 by the image data bus, and based on the image signal input via the image data bus. Then, the γ correction is performed by referring to the contents of the data ROM 217 in which the γ correction conversion table is stored. Further, when the multi-valued dither method is used as the gradation expression method, the dither processing is performed, and The laser diode driver 220 is controlled via O218 and parallel I / O219. The laser diode 221 is the laser diode driver 22.
The light emission is controlled by 0. The print head control unit 202 is connected to the printer control unit 201, the image signal processing unit 20, and the image reader control unit 101 by a bus and is synchronized with each other.

(B) Image Signal Processing (b-1) Configuration of Image Signal Processing Section FIG. 4 is a perspective view of the reading section. 3 wavelengths in the reading section
Light source (halogen lamp) with spectral distribution of (R, G, B) 1
The surface of the original 91 is illuminated by 2 and the reflected light is linearly imaged by the rod lens array 13 on the light receiving surface of the contact type CCD color image sensor 14. The optical system including the rod lens array 13, the light source 12, and the CCD color image sensor 14 is line-scanned in the direction of the arrow in FIG. 1, and the CCD color image sensor 14 converts the optical information of the document 91 into an electric signal.

FIG. 5 is a block diagram of the image signal processing section 20, and referring to this figure, processing of the image signal from the CCD color image sensor 14 to the print head control section 202 via the image signal processing section 20. The flow of is explained.
In the image signal processing unit 20, the image signal photoelectrically converted by the CCD color image sensor 14 is converted into an A / D signal.
The converter 61 converts the multivalued digital image data of R, G and B. The clock generator 70 generates a clock and transmits the clock to the CCD sensor 14 and the A / D converter 61. The converted image data is the reflection data of the original 91 after being subjected to a predetermined shading correction in the shading correction section 62, and therefore, in the density conversion section 63.
Log conversion is performed to convert the density data of the actual image. Further, the black generation unit 64 generates true black data K ′ from the R, G, B data.

On the other hand, for the shading-corrected image data, the area discriminating unit 65 extracts image features of each pixel for a local area to which the pixel belongs, and a density flat portion, an edge portion, and an intermediate portion of the image are extracted. Is divided. FIG. 6 shows a circuit configuration of the area discriminating unit 65. In the image data R, G, B output from the shading correction unit 62, after the edge detection unit 84 detects an edge, the MTF correction control unit 85 outputs 2-bit filter selection signals FS ₁ and FS ₀ to the MTF correction unit. Send to 67. on the other hand,
The image data R, G, and B are filtered by the smoothing processing unit 81, and then undercolor removed / blackened (UCR).
/ BP) control section 82 and color correction masking control section 83, and 2 bits (4
Step) achromatic color chromatic determination signal US ₁ , US ₀ and 2 bits
(4 types) of masking coefficient selection signals MS ₁ and MS ₀ are output.

Then, in the color correction processing unit 66, black data generation processing and masking processing are performed corresponding to the achromatic color chromatic color determination signals US ₁ and US ₀ and the masking coefficient selection signals MS ₁ and MS ₀ from the area determination unit 65. At the same time. That is, black data is generated and subtracted from the read data, and the read data is converted into data of three reproduction colors of C, M and Y. Further, in the MTF correction section 67, a digital filter is selected corresponding to the filter selection signals FS ₁ and FS ₀ from the area discrimination section 65, and smoothing (smoothing) processing or edge enhancement processing is performed. Next, the magnification / movement unit 6
At 8, the magnification is changed. Further, the color balance unit 69 adjusts the color balance and outputs the data to the print head control unit 202. It should be noted that the print head control unit 202 sends a signal M / NC indicating the monochrome mode or the full color mode to the image signal processing unit 20.

In FIG. 7, a register 87 includes a data bus (D _{7 to} D ₀ ) from the print head controller 202, an address bus (MA _{2 to} MA ₀ ), and a chip selection signal NCS.
_1. Various control parameters are set by the write signal NWR. Then, the control parameters REF0, REF
1 and REF2 are sent to the undercolor removal / blackening control unit 82, and the control parameters REF3 and REF4 are set to the MTF correction control unit 8
5, and sends the control parameter EDG to the MTF correction unit 67.

(B-2) Area determination result and outline of image signal processing Hereinafter, each processing of the image signal processing will be described in detail, but before that, the area determination and an outline of processing corresponding thereto will be described. In this embodiment, the area discriminating unit 65 extracts the following three features from the read data of R, G, and B for each pixel in a local area centered on the pixel. (a) Achromatic color or chromatic color (achromatic color chromatic color determination signal US)
(Refer to section (e-3)), (b) Edge detection (filter selection signal F
S) (see (h-2)), (c) Hue determination (masking coefficient selection signal MS) (see section (f-2)). And achromatic or chromatic,
Also, in accordance with the determination result of the edge detection, the black correction amount (UCR ratio / BP ratio) in the color correction processing unit 66 is as follows.
Is optimized, and in the MTF correction unit 67,
Smoothing or edge enhancement is performed by spatial digital filter processing. (1) Achromatic color and flat density: The black amount is increased corresponding to the result of the achromatic chromatic color determination, and the reproduced color M, C, Y data is smoothed. (2) When both achromatic color and chromatic color are at the edge part: The result of the achromatic color chromatic color determination is canceled, the black amount is reduced, and the edge enhancement is performed for C, M, and Y which are reproduced colors. (3) When the density is chromatic and flat: The black amount is reduced corresponding to the result of the achromatic chromatic color determination, and M, C,
Smooth the Y data. (4) In other cases, the black amount is intermediate and neither edge enhancement nor data smoothing is performed. In addition, a linear masking coefficient corresponding to each of a plurality of color groups is prepared in the color correction processing unit 66, and masking processing is performed using the linear masking coefficient of the color group to which the hue belongs, in accordance with the result of the hue determination. To do. In the monochrome mode, the black amount is set to 0 and the linear masking coefficient for the monochrome mode is used.

(C) Density Converting Section In the density converting section 63, the output density of the CCD color image sensor 14 is the original density (OD) as seen by the human eye.
To have a linear characteristic. CCD
The output of the color image sensor 14 has a photoelectric conversion characteristic that is linear with respect to the incident intensity (= original reflectance OR). On the other hand, the original reflectance (OR) and the original density (OD) are −
There is a relation of logOR = OD. Therefore, using the reflectance / density conversion table, the CCD color image sensor 1
The non-linear reading characteristic of 4 is converted into a linear characteristic. Specifically, using the reflectance / density conversion table 347 of FIG. 10, the R, G, B read data of the pixel of interest is converted to the density data D.
Convert to R, DG, DB.

(D) Black generation part Cyan, magenta, yellow necessary for full color reproduction,
The black color data C ′, M ′, Y ′, and K ′ are created for each scan by a frame sequential method, and a full color is reproduced by a total of four scans. Here, the reason why black is also printed is that even if cyan, magenta, and yellow are superimposed to reproduce black, it is difficult to reproduce clear black due to the influence of the spectral characteristics of each toner. So, in this full color copier,
The reproducibility of black is improved and full color is realized by the subtractive color mixture method using the data Y ′, M ′, C ′ and the black printing using the black data K ′.

The black generator 64 obtains the black amount K from the red, green, and blue components R, G, B representing the brightness on the original as follows. DR, DG, and DB obtained from the density conversion unit 63 are
Since these are density data of R, G, B components, they coincide with C ', M', Y'components of cyan, magenta, and yellow which are complementary colors of R, G, B in the CCD reading unit. Therefore, as shown in FIG. 8, the minimum values of DR, DG, and DB may be black data K'because C ', M', and Y'on the document are color-superposed components. Therefore, the black generation unit 64 detects black data K ′ = MIN (DR, DG, DB).

Then, as described later, when the reproduction color data C, M, Y is created in the color correction processing unit 66, the data K'from the black generation unit 64 is used and C ', M', Y is used. '
When the black data K is created by subtracting α · K ′ from the data of β, β · K ′ is output as the K amount. Where α
Is a UCR (undercolor removal) ratio described later, and β is B
P ratio. Note that in order to improve the black reproducibility, the parameters α and β are changed in four steps according to the characteristics of the local area including the target pixel after the smoothing process.

Next, the circuit of the black generator 64 shown in FIG. 9 will be described. The comparator 301 compares the red data DR and the green data DG, and the 2-input multiplexer 302 outputs the smaller value of DR and DG to the comparator 303 based on the comparison result. This comparator 303
This output value is compared with the blue data DB, and the 2-input multiplexer 304 determines DR, DG and DB based on the comparison result.
The minimum value of is output to the 2-input multiplexer 305. Two
The input multiplexer 305 is based on the signal M / NC,
This minimum value (full color mode) or 0 (single color mode) is output. That is, the signal M / NC determines the image output mode. At the "L" level, the full-color mode is output, and the above minimum value is output, but at the "H" level, the single-color mode is output, and K'is actually It may be set to an appropriate value that optimizes the output result of. In this embodiment, K '= 0 is fixed and the black printing data K'is cleared. The delay circuits 306, 307, 308 are used to match the timing. The output data is read data R, G,
I changed the display to C ', M', Y'in the meaning that B is the data of cyan, magenta, and yellow, which are complementary colors.
Substantially the same data is shown.

(E) Undercolor removal / black addition automatic control in area discrimination unit (achromatic color chromatic color determination) The area discrimination unit 65 is undercolor removal / black addition automatic control, automatic masking control, edge enhancement / smoothing. Region discrimination processing is performed for automatic control, and correction parameters are output. Here, the undercolor removal / black printing automatic control will be described.

(E-1) Purpose of Undercolor Removal / Black Printing Automatic Control (Achromatic Color Chromatic Color Judgment) As described above, in the black generation unit 64, the black data K '
As K '= MIN (DR, DG, DB) is detected. Then, in the color correction processing unit 66, from C ′, M ′, Y ′, α ·
When subtracting K'to create data K, β · K '
Output as a quantity. Here, α is the UCR ratio and determines the black amount. β is the BP ratio and lowers the color data. The UCR ratio / BP ratio has an influence on the saturation of color reproduction and the definition of achromatic color.

The reproducibility of achromatic color is determined by the UCR ratio / BP ratio (-
When α / β) is increased respectively, the reproduction is made in pure black K ′, which is improved, but the saturation of the chromatic color is decreased because the output ratio of K ′ is increased. Therefore, by controlling the UCR ratio / BP ratio by determining whether or not there is an achromatic color, it is considered that both the improvement in the achromatic color definition and the improvement in the chromatic color saturation can be achieved.

However, if the read data R, G, B (primary color system) is simply judged as to whether it is an achromatic color or not, then an erroneous judgment is likely to occur, which in turn leads to deterioration of the image. Causes of this erroneous determination include erroneous determination due to moiré of a halftone dot original in the reading system, and erroneous determination due to an error and noise in the reading system in an original having uniform density, hue, and a portion where the brightness changes gently.

Therefore, first, the read data R,
For G and B, smoothing processing (weighted moving average processing in the embodiment) is performed on the local area including the pixel. Next, it was decided to compare the R, G, and B levels to judge the achromatic color. Further, in order to improve the black reproducibility, the parameters α and β are changed in four steps (see FIG. 11) according to the characteristics of the area including the target pixel after the smoothing process, and the UCR ratio becomes closer to the achromatic color. The / BP ratio was increased.

(E-2) Smoothing processing For automatic undercolor removal / black addition automatic control, smoothing processing is first performed on a region of 5 × 5 = 25 pixels centering on the pixel of interest. In the smoothing processing unit 81 shown in FIG. 10, 8 bits (level 0 to 25) standardized by the shading correction by the shading correction unit 62 are used.
A moving average of weighted addition is performed on the target pixel for each color using the 5 × 5 filter 344 from the R, G, B data of 5). That is, first, the four line memories 340, 3
Data of 4 lines are sequentially stored in 41, 342, and 343. Then, the data R2 (G2, B2) of these four lines,
From R3 (G3, B3), R4 (G4, B4), R5 (G5, B5) and the data R1 (G1, B1) of the line currently being output,
After smoothing the center pixel of the center line by the filter 344 for smoothing processing, the smoothed data RS (GS, BS) is supplied to the undercolor removal / blackening control unit 82 and the color correction masking control unit 83. send. In the filter 344, weighting is performed gently centering on the pixel of interest.

By the smoothing process using the filter 344, it becomes possible to prevent the pseudo resolution with respect to the high frequency of the pixel and to extract the low frequency component. This allows
With respect to the object of area discrimination, (a) noise removal of an image with uniform density, (b) removal of moire caused by a dot image reading system, (c) gently changing hue, lightness, and saturation There is an effect of smoothing the image, and the discrimination accuracy is improved. The smoothed data RS (GS, BS) is used for hue determination (automatic masking control) in the undercolor removal / blackening control unit 82, and achromatic color chromatic color determination (UCR) in the color correction masking control unit 83. / BP automatic control).

(E-3) Achromatic color chromatic color determination The undercolor removal / blackening control unit 82 utilizes the fact that the read data of three colors is R≈G≈B for the determination of achromatic color (black). I am doing it. FIG. 11 shows a distribution area diagram for this determination. This determination is made for each pixel. In FIG. 11, the smoothed data RS, GS, BS of each pixel is 2
Range KLVL0 (GS-RE delimited by the solid line in the book
F0 <RS, BS <GS-REF0), a range KLVL1 (GS-REF1 <RS, BS separated by two one-dot chain lines
<GS-REF1) Range KL separated by two broken lines
VL2 (GS-REF2 <RS, BS <GS-REF2)
Corresponding to the above, as shown in the selection table of Table 1, the achromatic color to the chromatic color are classified into four distribution areas, and correspondingly, the achromatic color chromatic color determination signals US ₁ and US ₀ are generated. Here, if it is within the area indicated by KLVL0, it is determined to be achromatic, and if it is outside the area indicated by KLVL2, it is determined to be chromatic, but two areas are provided in the middle. . Then, the 2-bit achromatic chromatic color determination signal US ₁ ,
The value of the UCR ratio / BP ratio (-α / β) is changed stepwise in correspondence with the values 0, 1, 2, 3 represented by US ₀ . This ratio has a higher value as it is achromatic.

[0036]

[Table 1]

Undercolor removal / blackening control unit 82 shown in FIG.
In the circuit of Fig. 1, the data RS, GS, BS of each pixel are
It is determined which distribution region 1 belongs to and achromatic color is determined. In this determination, a constant value is added to or subtracted from the reference color data (GS) to determine the level difference from the other two colors. That is, the subtractor 361 and the adder 362 perform subtraction and addition with REF0 on the GS data,
GS-REF0 and GS + REF0 are obtained. And 12
These four are compared with RS, GS and BS in four comparators in the comparator 367 consisting of one.
Then, the result is passed through the NAND gate 369 to G
N when S-REF0 <RS, BS <GS + REF0
KLVL0 = “L” is output to the table (ROM) 372. Similarly, the subtractor 363 and the adder 364 perform subtraction and addition with REF1 on the GS data,
-REF1 and GS + REF1 are obtained. Then, the four comparators in the comparator 367 compare these RS and BS. And the result is NA
Through the ND gate 370, GS-REF1 <RS, B
When S <GS + REF1, NKLVL1 = “L” is output to the table 372. Further, the GS data is subjected to subtraction and addition with REF2 in a subtractor 365 and an adder 366 to obtain GS-REF2 and GS + REF2. Then, the four comparators in the comparator 367 compare these with RS and BS.
Then, the result is passed through the NAND gate 371 to G
N when S-REF2 <RS, BS <GS + REF2
KLVL2 = “L” is output to the table 372. In the table 372, according to the selection table of Table 1,
2-bit achromatic chromatic determination signals US ₁ and NS ₀ are output.

Here, in the table 372, MT
The filter selection signal FS input from the F correction control unit 85
_{When 0} is “L” (edge portion), the above determination is canceled. That is, the achromatic color chromatic color determination signals US ₁ , US ₀ = “3” for reducing the black amount are output. Filter selection signal FS
₀ is output when the edge detection amount of the R, G, B data in either the main scanning direction or the sub scanning direction is equal to or higher than a certain level (REF3). In this case, since it is the edge portion of the image, it is likely that the achromatic color chromatic color determination is erroneous. Therefore, for the pixels determined to be the edge portion of the image, the achromatic color chromatic color determination is performed in advance. The processing is set not to be performed to reduce the rate of erroneous determination. In other words, since the undercolor removal / blackening control is optimized only in the portion where the image density is relatively uniform, the image deterioration due to erroneous determination is eliminated.

As described above, the undercolor removal / blackening control unit 82 and the color correction masking control unit 83 shown in FIG.
Then, various selection signals (US ₁ ,
US ₀ , MS ₁ , MS ₀ , FS ₁ , FS ₀ ) are generated and output to the color correction processing unit 66 and the MTF correction unit 67.

(F) Automatic masking control (hue determination) in the area discriminating section (f-1) Purpose of automatic masking control In order to reproduce full-color input data in an image, a masking calculation is performed in the MTF correcting section 37. The linear masking coefficient is set so that the average color difference is minimized over almost the entire color gamut, but the color difference does not always become minimum in a part of the color gamut, and color reproduction errors and gradation errors do not occur. It gets bigger. Therefore, DR, DG, D
The B term and its squared term and DR, DG, DG, DB, DB
It is said that the secondary masking process with the addition of the DR term is good, but the circuit configuration becomes complicated and large-scale.
Therefore, in this embodiment, although the linear masking process is used, four groups to which each hue belongs (primary color group,
A plurality of linear masking coefficients corresponding to complementary color groups and two intermediate groups) are prepared in the color correction processing unit 66, the hue of the image data is determined in the color correction masking control unit 83, and the hue is determined according to the hue. A masking coefficient that minimizes the color difference within the hue is selected to obtain color reproducibility similar to that of the secondary masking process. In the masking process as well, in the case of the achromatic color / chromatic color determination, similarly, the erroneous determination is less likely to occur by using the data RS, GS, BS subjected to the smoothing process in the smoothing processing unit 81 of FIG.

(F-2) Hue Judgment The hue judgment in the color correction masking controller 83 is as shown in FIG.
2, the color correction table (ROM) 368 is used. Here, the address A of the color correction table 368
_{3 to 8} bits of RS, GS, and BS data are input to _{8 to} A ₀ , and correspondingly, 2-bit masking coefficient selection signals MS ₁ and MS ₀ are output.

The hues are R, G, B and W systems (primary color systems) and C,
It is classified into two groups of M, Y and BK (complementary color) and an intermediate group. Here, each R as shown in FIG.
Consider a cube with S, GS and BS data as coordinate axes.
Each vertex of the cube is cyan (C), green (G), blue (B), white (W)
Represents the pure component of. Therefore, the R, G, B, W group is located in four small cubes including the vertices of (R), (G), (B), and (W). The same applies to the C, M, Y and BK group. One of the intermediate groups is located on the outline of a large cube that surrounds the regular cube of the R, G, B, W group, and the other intermediate group surrounds the regular cube of the C, M, Y, BK group. Located on the outline of a large cube. As shown in the figure, if the (R), (M), (BK), and (B) planes are taken as an example, the area
(I) is a C, M, Y, BK group, and is a region (II)
Is an intermediate group close to C, M, Y, BK,
(III) is an intermediate group close to the R, G, B, W group, and region (IV) is an R, G, B, W group. As described above, R, G, B-based masking and C, M, Y-based masking are roughly divided into two groups (R, G, B) and (C, M, Y) having proper hues. This is because they are sparsely distributed.
In other words, if color samples that are appropriately sparsely distributed are used, masking coefficients to be described later do not take significantly different values. Therefore, when the (R, G, B) system and the (C, M, Y) system are discriminated, there is no great trouble even if an erroneous determination is made. Furthermore, the reason for dividing the middle part into two is to make it difficult to cause an obstacle even if an erroneous determination is made.

In the color correction table 368, the input R
According to the S, GS, and BS data, it is determined which group of the regular cube it belongs to, and when the determination result is (I), MS ₁ , ₀
= Output "3", when the (II), and outputs the MS _{1, 0} = "2", and outputs the, MS _{1, 0} = "1" when (III),
In the case of (IV), MS ₁ , ₀ = “0” is output.

(G) Color Correction Processing Section The color correction processing section 66 is provided in the CCD color image sensor 14
The transmission characteristics of the respective filters R, G, B inside and the reflection characteristics of the toners C, M, Y of the printer section are corrected to match the color reproducibility to a characteristic close to ideal. The G filter and the M toner will be described as an example. As shown in the transmission characteristics of FIG. 14 and the reflection characteristics of FIG. 15, the characteristics of the G filter and the M toner are indicated by the shaded areas as compared with the ideal characteristics. There is a non-ideal wavelength range. In order to perform this correction, the color correction processing unit 66 performs the linear correction by the following masking equation together with the black printing process described above. (Since the printing is performed in the frame sequential manner, this masking equation is executed line by line.

[0045]

[Equation 1]

K '= MIN (DR, DG, DB)

In the circuit of the color correction processing unit 66 shown in FIG. 16, a parameter U set by the color correction register 826 corresponding to the correction parameter determined by the area discrimination unit 65.
Black printing control and color correction masking processing are performed according to the CR ratio / BP ratio (-α / β). These various coefficients are set in the color correction register 826 shown in detail in FIG. 17 according to the nature of the area.

As shown in the circuit diagram of FIG. 17, the color correction register 826 has a masking coefficient (A _ci ,
B _ci , C _ci , A _mi , B _mi , C _mi , A _yi , B _yi , C _yi ) (This is 3
× 3 matrix M _k elements _{(M) ji (j = c} , m, y; i = 1,2,
3)), the UCR ratio / BP ratio (-α / β), and d are output. _{Here, MS 1, 0 = "0} " first masking coefficient M ₀ is selected when (k = 0) is a coefficient small R, G, the color difference with respect to B is primary-, MS _{1, 0} = "3" fourth masking coefficient M ₃ that is selected when (k = 3) is reduced C, M, the color difference with respect to Y and the complementary color system. further,
Second masking coefficient selected when MS ₁ , ₀ = “1”
(k = 1) is weighted to the masking coefficient for the primary color system.
_{(2/3) M 0 + (1/3} ) to select a masking coefficient is M _3, also a third masking coefficients that are selected when the _{MS 1, 0 = "2"} (k = 2) is , A masking coefficient which is (1/3) M ₀ + (2/3) M ₃ weighted to the masking coefficient of the complementary color system is selected. The reason why the masking coefficient of the intermediate group is set by mixing the masking coefficient for the primary color system and the masking coefficient for the complementary color system is to make the hue change due to an erroneous determination inconspicuous during color reproduction.

The following matrix shows the R, G, B masking coefficients M ₀ .

[Equation 2] Further, the following matrix is a masking coefficient M for C, M, Y.
₃ is shown.

[Equation 3] For comparison, a conventional normal masking coefficient is shown below.

[Equation 4]

That is, the color correction register 826 of FIG.
In the circuit diagram of FIG. 6, a level 861 indicates a data bus (MD _{7 to} MD ₀ ), an address bus (MA _{4 to} MA ₀ ), and a chip selection signal NCS ₀ from the print head controller 202.
Data is set by the NWR signal. That is,
The above-mentioned four types of matrix coefficient data of each color are output to the multiplexers 862, 863, and 864, respectively. The multiplexers 862, 863, 864 select one type of matrix coefficient corresponding to the selection signal MS ₁ , ₀ from the color correction masking control unit 83, and the two-input multiplexer 86
5, 866, 867. On the other hand, the two-input multiplexers 865, 866, 867 are also supplied with the coefficients Dc, Dm, Dy for the single color mode. Multiplexer 865,
One of 866 and 867 selects and outputs one by the mode selection signal M / NC. On the other hand, four UCR ratio / BP ratio is selected by the signal US _{1, 0} by multiplexer 868. The constant d is used to increase the saturation at low density, but the description is omitted here. In the above processing, d = 0 is set for simplification of description.

The circuit of the color correction processing unit 66 of FIG. 16 will be described. First, in the black-printing unit, in the undercolor removal control for printing C, M, Y, the multiplier 824 causes the black generation unit 64 to output the black color. Of the black data K ′ is multiplied by the UCR ratio (−α) from the color correction register 826. Then, this multiplication value (−α · K ′) is added to the complementary color data C ′, M ′, Y ′ by the adders 821, 822, 823 to obtain the undercolor removal values C ₁ , M.
Output as ₁ and Y ₁ . On the other hand, in the black printing control for printing K, the multiplier 824 multiplies the BP ratio β from the color correction register 926, and the multiplied value (β · K ′) is added via the limiter circuit 834. Send to 835.

Further, in the color correction masking section, a linear masking process having a simple circuit structure is used, and in the undercolor removal control, the multipliers 831, 832 and 833 apply the data C ₁ , M ₁ and Y ₁ to the data C ₁ , M ₁ and Y ₁ , respectively. The masking coefficients (A _{c to} C _c , A _{m to} C _m , A _{y to} C _y ) from the color correction register 826 are multiplied. Then, the multiplication values C ₂ , M ₂ and Y ₂ are added to the adder 83.
Added in 5, and output as VIDEO1 data. At this time, the output from the limiter circuit 834 is cleared to “00”, and the adder 835 outputs the addition result of C ₂ , M ₂ and Y ₂ .

On the other hand, during the black printing control, the color correction register 826 sets "00" in the multipliers 831, 832 and 833, so that C ₂ , M ₂ and Y ₂ are cleared and K ₁ (= K ₂ )
Only the data is output as VIDEO1 data through the limiter 834.

To show the masking correction effect, first, FIG.
The CIE 19 shows the original color (represented by white circles) and the reproduced color (represented by black circles) when the above-mentioned normal masking coefficient is used.
This is represented by the L * a * b * color system of the 76 uniform color space. (The a * -b * plane shown in the figure represents hue and saturation, and the L * direction perpendicular to the paper surface represents lightness.) The deviation between the original color and the reproduced color corresponds to the color difference. Here, the average dye of only R, G, B is 10.5335, and the average color difference of only C, M, Y is 4.029. FIG. 19 is a diagram showing the original color (white circle) and the reproduced color (black circle) on the a * -b * plane when the above-described masking coefficient M ₀ for R, G, B is used. here,
The average color difference of only R, G, and B is 3.8576, and the hue shift is smaller than that in the case of a normal masking coefficient. The average color difference of only C, M, and Y is 12.1797. Further, FIG. 20 shows the original color (white circle) and the reproduced color (black circle) when the masking coefficient M ₃ for C, M, Y is used.
It is the figure represented by the * -b * plane. Here, the average color difference of only C, M, and Y is 2.43782, and the hue shift is smaller than that in the case of a normal masking coefficient. In addition,
The average color difference of only C, M, and Y is 12.7757. As clearly shown above, the selected masking factor reduces the color difference of the corresponding hues.

When the monochrome mode is set by the M / NC signal, color reproduction is performed in monochrome. Reproduction with a single color means the light and shade information based on the sensitivity (relative visual sensitivity) of perceiving brightness as a human sense C, M, Y, K, R (M + Y), G (B +
Y) or B (C + M) toner. Therefore, similar to the masking process, the relative visibility information
(MC) may be created by linear processing of masking coefficients DR, DG, and DB. MC = D _c · C '+ D _m · M' + D _y
Y'that is, the color correction register 826 sets Dc, Dm, and Dy as masking coefficients, and thereby VID
MC data is output as EO1 data. The masking coefficients Dc, Dm, Dy are determined in accordance with the relative luminosity depending on the type of toner. At this time, as described above, the black printing process is not performed. That is, in the black generation unit 64 shown in FIG. 9, in the monochrome mode, K ′ =
"00" is output.

(H) Edge Enhancement / Smoothing Automatic Control in Area Discrimination Unit (h-1) Purpose of Edge Enhancement / Smoothing Automatic Control Generally, for a single color image, characters / photographs are printed according to the density change or density distribution of the image. The automatic identification is performed, the edge enhancement is performed on the character image, and the smoothing process is performed on the photographic image, so that both sharpening and smoothing of the image are compatible with each other to optimize the MTF correction.

However, in the case of a color image, such an identification does not always work well because the image density changes with a change in hue and saturation by merely edge enhancement. For example, when changing from white to red, the edge may be emphasized, but when changing from red to cyan, the hue changes strangely at the edge, so it is better not to emphasize the edge. The skin color etc. has a great influence. Therefore, only the change in image brightness must be extracted and controlled.

(H-2) Edge detection In the edge detection unit 84 shown in FIG. 10, the pixel of interest is selected from the 8-bit R, G, B data (level 0 to 255) standardized by the shading correction in the shading correction unit 62. Edge detection is performed in the main scanning direction and the sub-scanning direction for each color in the area around. That is, first, four lines of data are sequentially stored in the four line memories 340, 341, 342, 343. And, the data R2 (G2, B2), R3 (G3, B3), R4 (G4, B) of these four lines
4), R5 (G5, B5) and the data R of the line currently being output
1 (G1, B1), the data of the central pixel of the central line is detected by the filter 345 for edge detection in the main scanning direction and the filter 346 for edge detection in the sub-scanning direction, and then the MTF correction control is performed. Output data RE1 (GE1, BE1), RE2 (GE2, BE2) in both directions are provided in the section 85.
Send each.

In the edge detection using the filters 345 and 346 described here, the inclination amount and the inclination direction of the pixel of interest with respect to the two directions of the main scanning direction and the sub scanning direction are extracted. Here, the inclination amount is the output data RE1 (GE1,
BE1) and RE2 (GE2, BE2) are absolute values, and the inclination direction is its sign (positive or negative). A hue change represented by a color ghost phenomenon occurs at an edge portion (a portion where the brightness changes abruptly) of the image. Therefore, this output data is extracted by the MTF correction control unit 85 from a portion in which an erroneous determination of the achromatic color / chromatic color determination is likely to occur and selectively MTF.
It is used to divide the area to be corrected.

The data of the pixel of interest in the center line is sent to the density conversion section 63, as described above.
Using the reflectance / density conversion table 347, the density data D
Converted to R (DG, DB).

FIG. 21 shows a circuit of the MTF correction controller 85 for performing the MTF automatic control. In this circuit,
Based on the signal from the edge detection unit 84, the density flat portion, the edge portion, and the intermediate portion of the image are separated. The density flat portion means R, G, and R in both main scanning and sub scanning directions.
The threshold value (RE
F3) and below. That is, the density flat portion is an area in which the change in brightness is small for any color data. At this time, the filter selection signal FS ₀ = “L” is output. On the other hand, the edge portion is either the main scanning direction or the sub-scanning direction, and the edge detection amount of R, G, B data is equal to or more than a certain threshold value (REF4), and R, G, B This is an area where the tilt directions of the B data are the same. At this time, the filter selection signal FS ₁ = “L” is output. Here, in order to prevent erroneous judgments due to hue changes, changes in brightness between achromatic colors (white ← → background level such as black ← → black characters / thin lines) or changes between achromatic and chromatic colors (white ← → Base level such as color patch ← → Extract red / blue characters, thin lines) as edges. If both filter selection signals are not "L", it is an intermediate part.

In the MTF correction control circuit in FIG. 21, the edge detection amounts RE1 and GE detected in the main scanning direction are detected.
1 and BE1 are absolute value detection circuits 381 and 38, respectively.
2, 383, it is converted into absolute values RE1 ', GE1', BE1 '. The absolute values RE1 ′, GE1 ′, BE1 ′ are compared with the threshold value REF3 in the comparator 390, and when the total absolute value is smaller than the threshold value REF3, the negative logic AND gate 391 is passed to the negative logic AND gate 395.
Is sent to. Absolute value RE1 ', GE1', BE1 '
Similarly, in the comparator 390, the threshold value RE
F4, and if the total absolute value is larger than the threshold value REF4, the negative logic AND gate 392 is operated to perform the negative logic AND.
A signal is sent to gate 396. On the other hand, the edge detection amount RE
1, GE1 and BE1 detect a slope (sign) at an edge in the slope determination circuit 384, and the sign is a negative logical AND.
It is output to the gate 396. Therefore, in the negative logic AND gate 396, when the edge detection amount is larger than the threshold value REF4 in the main scanning direction and the inclination directions of the R, G, B data match (when it is determined to be an edge portion). To the filter selection signal FS ₁ (=
"L") is output.

Similarly, the edge detection amounts RE2, GE2, and BE2 detected in the sub-main scanning direction are absolute values RE2 ', GE2', and GE2 ', by absolute value detection circuits 385, 386, and 387, respectively.
Converted to BE2 '. This absolute value RE2 ', GE2', B
E2 ′ is the threshold value REF in the comparator 390.
3 and the total absolute value is smaller than the threshold value REF3, the signal is sent to the negative logic AND gate 395 through the negative logic AND gate 393. Therefore, the negative logic AND gate 395 outputs the filter selection signal FS ₀ when the edge detection amount is smaller than the threshold value REF3 in both the main scanning direction and the sub scanning direction (density flat portion). Similarly,
The absolute values RE2 ′, GE2 ′, BE2 ′ are calculated by the comparator 39
At 0, it is compared to the threshold value REF4, and if the total absolute value is greater than the threshold value REF4, a signal is sent to the negative logic AND gate 397 through the negative logic AND gate 394. On the other hand, with respect to the edge detection amounts RE2, GE2, and BE2, the inclination (sign) at the edge is detected by the inclination determination circuit 388, and the sign is output to the negative logic AND gate 396. Therefore, the negative logic AND gate 396 has an edge detection amount larger than the threshold value REF4 in the sub-scanning direction,
And when the inclination directions of R, G, B data are the same
The filter selection signal FS ₁ (= “L”) is output to the (edge portion) through the negative logic OR gate 397. FIG. 22 schematically shows the edge detection amount (GE1) using the filter 345 when the G image data changes in the main scanning direction as shown in the lower side. This edge detection amount (GE1) is compared with threshold values REF3 and REF4 as shown on the upper side, and filter selection signals FS ₀ and FS ₁ are output corresponding to the results.
FS ₁ is output when either of the tilt signals NSINA and NSINB is “L”.

Threshold value R in MTF correction controller 85
EF3 and REF4 can be adjusted externally by sharpness setting (see FIG. 7). For example, to increase sharpness, REF3 and REF4 may be set low.

In this embodiment, REF3 <REF4
Is set, but REF3> RE depending on the purpose of processing
You may set it as F4.

(I) MTF correction section Filter selection signal F set by MTF correction control section 85
S ₁ and FS ₀ are spatial filter selection signals of the MTF correction unit 66. For the read data R, G, B, there is no edge in both main scanning and sub scanning for any color FS ₀ =
In the case of "L" (density flat portion), smoothing processing is performed on the data converted into C, M, Y, K data, and achromatic color chromatic color determination is permitted. Even if the achromatic color chromatic color determination is permitted, an image with low saturation looks like random image noise when the K amount changes significantly. Therefore, the MTF correction unit 67 performs a smoothing process to make the change inconspicuous. (This is also why the achromatic color judgment is classified into four stages. However, since this is not enough, we took measures to further reduce the noise even for the pixels judged as achromatic color. Also, image noise and moire caused by the reading system are reduced.
It is possible to smooth the part where the lightness, saturation, and hue change gently like a photograph.

When FS ₁ = “L” (edge portion), the output of the Laplacian filter 324 is permitted, addition with the target pixel is performed, and the edge enhancement processing of the image is performed. Therefore, in the achromatic edge portion, the sharpness of the image is performed without increasing the UCR ratio / BP ratio, so that the sharpness is improved.

The MTF correction unit 66 shown in FIG.
Edge enhancement and smoothing processing are performed by using a two-dimensional R digital filter. First, four lines of data are sequentially stored in the four line memories 320, 321, 322, 323. Then, the data of each line and the data of the line currently being output are processed by the 5 × 5 digital filter 324 for secondary differentiation (for edge enhancement) and the 5 × 5 digital filter 325 for smoothing. Output to the multiplier 326 and the 2-input multiplexer 328, respectively. The multiplier 326 outputs the product of the output value of the digital filter 324 and the value EDG to the 2-input multiplexer 327, and the 2-input multiplexer 32.
7 is a filter selection signal FS ₁ = “L” (edge portion),
The output value or "00" corresponding to "H" is added to the adder 3
To 29. On the other hand, the multiplexer 328 outputs the smoothed output value of the digital filter 325 and the output value of the target pixel that is not smoothed from the line memory 321 to the filter selection signal FS ₀ = “L” (density flattening portion), “H”. Corresponding to, and output to the adder 329. The adder 329 adds the two input values and outputs it as a signal VIDEO2.

The secondary differential filter 324 used for edge enhancement detects the edge enhancement amount of the image. The edge enhancement is the result of linear conversion of the edge enhancement amount obtained by this filter and the central pixel. And (addition of original image + second derivative). That is, when FS ₁ = “L” (edge portion), the edge-enhanced data is added to the data of the target pixel in the adder 329.

On the other hand, the filter 325 used for the smoothing process reduces the image noise by using the moving average by weighted addition of the peripheral pixels and creates smooth image data. (The weighted addition prevents false resolution such as moire due to the filter processing.) That is, FS ₀ = “L”
In the case of (density flat portion), only the smoothed data is output from the adder 239.

The EDG value that affects the edge enhancement in the MTF correction unit 66 can be adjusted from the outside by the sharpness setting (see FIG. 7). For example, to increase sharpness, the EDG value may be increased.

In the MTF process described above, the read data R, G, B are sharpened and smoothed in the image data. This is because if the same processing is performed on the reproduced color data C, M, and Y, the edge emphasis is applied even to the hue change portion, and conversely the color reproducibility deteriorates. Therefore, the MTF correction is selectively performed by extracting the brightness change of the read data.

[0073]

As described in detail above, according to the present invention, image features are extracted in a local region centered on a pixel of interest, so that image feature extraction can be performed with less erroneous determination, and image reproducibility is improved. improves.

Furthermore, by filtering the input data according to the purpose of area determination, especially for color images,
The accuracy of each area judgment has been improved, and the reproducibility such as color reproducibility, sharpness of black, vividness of characters / thin lines, and reduction of image noise has become more accurate.

[Brief description of drawings]

FIG. 1 is a sectional view of a full-color copying machine.

FIG. 2 is a block diagram of a part of a control system.

FIG. 3 is a block diagram of another portion of the control system.

FIG. 4 is a perspective view of a reading unit.

FIG. 5 is a block diagram of an image signal processing unit.

FIG. 6 is a circuit diagram of an area discrimination unit.

FIG. 7 is a circuit diagram of a register for setting various parameters.

FIG. 8 is a graph showing the relationship between density data and black amount K ′.

FIG. 9 is a circuit diagram of a black generation unit.

FIG. 10 is a circuit diagram of a smoothing processing unit and an edge detection unit.

FIG. 11 is a graph showing four regions from achromatic colors to chromatic colors.

FIG. 12 is a circuit diagram of an undercolor removal / blackening control unit and a color correction control unit.

FIG. 13 is a diagram of a cube with a hue distribution.

FIG. 14 is a graph of characteristics of a G filter.

FIG. 15 is a graph of characteristics of M toner.

FIG. 16 is a circuit diagram of a color correction processing unit.

FIG. 17 is a circuit diagram of a color correction register.

FIG. 18 is a diagram showing a color difference when a normal masking coefficient is used.

FIG. 19 is a diagram showing a color difference when R, G, and B masking coefficients (M ₀ ) are used.

FIG. 20 is a diagram showing a color difference when a masking coefficient for C, M, Y (M ₃ ) is used.

FIG. 21 is a circuit diagram of an MTF correction controller.

FIG. 22 is a diagram of an example of edge detection.

FIG. 23 is a circuit diagram of an MTF correction unit.

[Explanation of symbols]

65 ... Area discrimination unit, 66 ... Color correction processing unit, 67 ... M
TF correction unit, 81 ... Smoothing processing unit, 82 ... Undercolor removal / blackening control unit, 83 ... Color correction masking control unit, 84 ... Edge detection unit, 85 ... MTF correction control unit,
US ₁ , US ₀ ... Achromatic chromatic color determination signal, MS ₁ , MS ₀ ...
Masking coefficient selection signal, FS ₁ , FS ₀ ... Filter selection signal.

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP 63-125055 (JP, A) JP 63-177683 (JP, A) JP 3-57375 (JP, A) JP 4- 165873 (JP, A) JP-A-2-162967 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H04N 1/40 H04N 1/46

Claims (4)

(57) [Claims] 1. Input means for inputting image data, filtering means for performing two-dimensional spatial digital filter processing on the input image data, and chromatic for the image data subjected to the filter processing.
On the basis of the image data that has been subjected to the filter processing , a determination unit that determines a color area and an achromatic area ,
Setting means for setting color correction parameters for performing color correction processing on input image data, on the basis of the set color correction parameters by the setting unit, the chromatic determination and region by said discrimination means an image forming apparatus characterized by comprising the in <br/> input image data and a correction means for performing color correction processing. 2. Input means for inputting image data, smoothing means for performing smoothing processing on the input image data, and chromatic color for the image data subjected to the smoothing processing.
Discriminating means for discriminating the region and the achromatic region, a setting unit on the basis of the smoothing processing is image data subjected to set the color correction parameters for performing color correction processing on input image data, wherein And a correction unit that performs a color correction process on the input image data of the area determined to be chromatic by the determination unit based on the color correction parameter set by the setting unit. A characteristic image forming apparatus. 3. The image processing apparatus according to claim 1 or 2, wherein the color correction process is a masking process,
An image forming apparatus, wherein the color correction parameter is a masking coefficient. 4. The image processing device according to claim 3.
And the discrimination means discriminates the hue,
The color coefficient is a masking factor according to the determined hue of the image.
An image forming apparatus characterized by being a number.