JP2000201276A - Color correction device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a color correction device which can satisfactorily color- match the originals of various glossiness. SOLUTION: In the color correction device, a means 5 inputting picture signals RGB using a picture input device such as a scanner, a means 9 correcting the input picture signals RGB, a means 10 converting the corrected RGB signals into the values of lightness L, saturation C, and a hue H, a means 14 inputting the glossiness of an original, a means 11 correcting lightness by the gloss degree of the original, a means 12 correcting saturation by the glossiness of the original and a means 13 converting obtained lightness L, saturation C and the hue H into RGB values are installed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color correction device for a color image input device for correcting the influence of glossiness of a document.

[0002]

2. Description of the Related Art FIG. 1 shows an overall configuration diagram of a color image input / output device. Reference numeral 1 denotes a color scanner, which is a color image reading device, which generates RGB signals from a color image via a CCD. Reference numeral 2 denotes a computer which performs arithmetic processing on RGB input signals from the color scanner 1 and displays the processed signals on a display 3. Reference numeral 4 denotes a color printer, which converts the RGB input signals from the color scanner via the computer 2 into RGB signals having undergone arithmetic processing into CMYK signals, which are the four primary colors of printing, and prints a color image.

There are various types of color images read by a color scanner, such as glossy or matte. Light is scattered by the gloss of the document, which affects the reading of the filter of the color scanner, and the color of the document differs from that of the document.

Therefore, conventionally, glossy originals have been corrected in a color correcting section of a color scanner by the following method.

FIG. 9 shows the configuration of a conventional scanner color correction unit. Reference numeral 39 denotes a color correction unit that corrects color deterioration due to the spectral characteristics of the CCD of the color scanner. Reference numerals 40 to 42 denote one-dimensional corrections, which convert each level of the input RGB one-dimensionally. With the corrections of 40 to 42, the color matching is performed between the glossy original and the glossy original by changing the coefficient.

This method can correct the lightness among the three attributes of lightness, lightness, saturation, and hue. However, after reading a glossy color image original with a scanner and performing conventional scanner color correction, the color image output to the printer or display loses color compared to the original, and the saturation decreases considerably, There has been a problem that good color correction cannot be performed on glossy color documents.

[0007]

As described above, when an original having various glosses is read by a scanner and an image is reproduced by a display or a printer, the reading of the scanner is affected by the gloss. Correspondingly, there is a problem that good color matching cannot be obtained.

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above problems, and has as its object to provide a color correction apparatus which can remove the influence of the glossiness of a document and obtain good color matching.

[0009]

In order to solve the above-mentioned problems, a color correction apparatus according to the present invention comprises: an image reading means for reading a document; a means for inputting an image signal read by the image reading means; Means for converting the image signal into lightness, saturation, and hue of three attributes of color, means for inputting the glossiness of the document, and gloss correction for correcting the brightness and the saturation by the input glossiness Means, and means for converting the corrected brightness, saturation, and hue into an image signal for output of an image output device.

With the above arrangement, good color matching can be achieved by performing correction based on gloss of a document for brightness and saturation.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION
Image reading means for reading a document, means for inputting an image signal read by the image reading means, means for converting the image signal into brightness, saturation, and hue of three attributes of color; Means for inputting, glossiness correction means for correcting the brightness and the saturation based on the input glossiness,
A color correction device comprising means for converting the corrected brightness, saturation, and hue into an image signal for output of an image output device, wherein correction of brightness, saturation from the glossiness of a color image document is performed. , The effect of gloss on the reproduced color can be removed, and good color matching can be achieved.

According to a second aspect of the present invention, there is provided image reading means for reading a document, means for inputting an image signal read by the image reading means, means for detecting glossiness of the document, Means for converting the signal into lightness, saturation, and hue of three attributes of color, glossiness correction means for correcting the brightness and the saturation by the detected glossiness, and the corrected brightness, saturation, and This is a color correction device having means for converting a hue into an output image signal of an image output device, and the glossiness of a color image document is automatically detected, and the glossiness need not be set.

According to a third aspect of the present invention, there is provided image reading means for reading a document, means for inputting an image signal read by the image reading means, means for designating a glossy area of the document, The signal is divided into three attributes of color: brightness, saturation,
Means for converting to hue, gloss correction means for correcting the brightness and the chroma by the designated gloss area, and the corrected brightness, chroma and hue to an output image signal of an image output device. This is a color correction apparatus characterized by having a conversion means, and the setting of the glossiness can be simplified by determining the glossiness area according to the type of the document.

According to a fourth aspect of the present invention, there is provided an image reading means for reading a document, a means for inputting an image signal read by the image reading means, a means for externally inputting the glossiness of the document, The image signal is represented by three attribute values of color,
Saturation, means for converting to hue, glossiness correction means for correcting the brightness and the saturation by the input glossiness,
A color correction device comprising means for converting the corrected brightness, saturation, and hue into an image signal for output of an image output device, wherein the glossiness is externally set and the glossiness is corrected. be able to.

According to a fifth aspect of the present invention, there is provided an image reading means for reading a document, a means for inputting an image signal read by the image reading means, a means for inputting glossiness of the document, Means for converting the signal into lightness, saturation, and hue of the three attributes of color, and using the input glossiness,
Brightness, calculating the correction amount of the saturation, means for creating a reference table, storage means for storing the reference table, glossiness correction means for correcting the brightness and the saturation by the stored reference table, A color correction device comprising means for converting the corrected lightness, saturation, and hue into an image signal for output of an image output device. Calculation can be performed in a short time.

According to a sixth aspect of the present invention, there is provided a dividing means for dividing an input color space of an arbitrary color image input device into three-dimensional figures, and corresponding to each vertex of the solid divided by the dividing means. Setting means for setting a vertex output value for each color separation component of the color image output device; and performing interpolation using the vertex output values set by the setting means to correspond to the input signal in the input color space. A color correction device comprising: an interpolation unit that obtains an output value to the output device, wherein the setting unit corrects three attributes of lightness, saturation, and hue by using the glossiness of the document. 5. The color correction device according to claim 1, wherein a vertex output value in said input color space is set after applying to each vertex of the space. Lookup table interpolation By performing high-speed processing of color correction processing can be realized.

According to a seventh aspect of the present invention, there is provided a color image input device for reading a plurality of color patches having a plurality of gloss levels, a means for storing colorimetric values of the color patches, 4. A device according to claim 1, further comprising means for obtaining a correction coefficient of a glossiness correction means from a readout value of said glossiness and said color chart corresponding to each glossiness value read by said color image input device and said colorimetric value. 5. The color correction device according to item 5, wherein a color patch having no gloss and a gloss is prepared as one color patch for calibration.
The color correction coefficient and gloss correction coefficient can be calibrated at once.

The invention according to claim 8 of the present invention is a program product for performing a color correction based on the glossiness of a color image input device which is affected by a color image input signal by the glossiness of a document. The inputted procedure is a step of inputting an image signal of a document, a step of inputting a gloss level of the document, a step of converting the image signal into brightness, saturation, and hue of three attributes of color, and a step of converting the brightness and the saturation. A step of correcting the glossiness to be corrected by the glossiness, and a step of converting the corrected lightness, chroma, and hue into an image signal for output of an image output device, as a software application by a storage medium storing the program. , Easy to provide.

According to a ninth aspect of the present invention, in the color correction apparatus according to any one of the first to eighth aspects, the original is a monochrome original or a color original.
For both color originals, it is possible to perform correction with the effect of glossiness removed.

According to a tenth aspect of the present invention, in the glossiness correcting means, three values of lightness, saturation, and hue of the image signal are provided.
The color correction apparatus according to claim 1, wherein glossiness correction is performed on at least two or more of the components, and a shift in brightness, saturation, and hue due to glossiness can be corrected.

(Embodiment 1) Hereinafter, Embodiment 1 of the present invention will be described with reference to FIGS.

FIG. 1 shows a configuration diagram of a color image input / output device according to the first embodiment of the present invention. 1 is a color scanner, and 2 is a computer which takes in RGB input signals of a color image.
The color correction is performed so that the B input signal matches the color image original, and the color image read from the color scanner is displayed on the color display 3. Reference numeral 4 denotes a color printer, which converts an input signal from a color scanner into CMYK, which is four primary colors for printing, and prints a color image.

In the color scanner 2, color correction is performed on the input RGB signals from the CCD according to the characteristics of the device, and the signals are output to the color display 3 and the color printer 4.

FIG. 2 shows a configuration diagram of the color correction processing of the color scanner according to the first embodiment of the present invention.

5 is a reading process of the color scanner.
Obtain the read value R0G0B0 from the color scanner.
Reference numerals 6 to 8 denote level conversion processes for independently converting each level of R0G0B0. Each level linearly compresses or expands the range of valid levels. By this level conversion processing, an R1G1B1 value is obtained.

Reference numeral 9 denotes a color correction process for performing a color correction process for correcting color deterioration due to the spectral characteristics of the CCD of the color scanner. The correction coefficient in this case is obtained using a color chart of a known glossiness. However, the correction coefficient is determined so that the output R2G2B2 value becomes the NTSC-RGB value of the light source D65.

[0027]

(Equation 1)

[0028]

(Equation 2)

Reference numeral 10 denotes a color space conversion process, which is performed by NT.
After converting from SC-RGB space to CIEL * a * b * perceived color space, L * ab (brightness), C * ab (saturation), H
Convert to ab ° (hue). NTSC-RG in (Equation 1)
After converting the equation for converting the B space into the CIEL * a * b * perceived color space into (Equation 2) the CIEL * a * b * perceived color space, L * ab (brightness) and C * ab (saturation) ), Hab °
Here is an expression to convert to (hue). A color space conversion process is performed on the R2G2B2 signal to obtain an L1C1H1 value.

Reference numeral 11 denotes a brightness glossiness correction process for correcting brightness based on the glossiness of the color image document. The input values are L1 and the glossiness K of the color image document. The brightness L2 corrected for glossiness is obtained.

[0031]

(Equation 3)

[0032]

(Equation 4)

In the first embodiment, the lightness L before glossiness correction is
The relationship between 1 and the lightness L2 after correction is expressed by (Equation 3), and the coefficient AL in (Equation 3) is obtained by (Equation 4) from the glossiness.
Regarding (Equation 4), it is concluded that the relationship between the glossiness and the slope AL is linear because the slope AL when comparing the brightness measured with a document with a different glossiness and the brightness of the value read from the scanner is different. I was asked. The values of a and b were obtained by actually measuring documents having different gloss.

Reference numeral 12 denotes a chroma gloss correction process for correcting the chroma based on the gloss of the color image document. The input values are the chroma C1, the hue H1, and the gloss K of the color image document. The chroma C2 corrected for glossiness is obtained.

[0035]

(Equation 5)

[0036]

(Equation 6)

In the first embodiment, the saturation C before the gloss correction is set.
The relationship between 1 and the corrected saturation C2 is represented by (Equation 5), and the coefficient AC in (Equation 5) is obtained from (Equation 6) from the glossiness and the hue value H. In the case of saturation, the influence of the gloss differs depending on the hue, that is, depending on the color. Therefore, the values of the coefficients A (H) and B (H) in (Equation 6) are determined by the hue H.

Reference numeral 13 denotes a value obtained from the L2C2H1 value which is L * ab (brightness), C * ab (saturation), and Hab ° (hue), and is represented by NT.
This is a process of converting to the SC-RGB space, and performs an inverse conversion process of the color space conversion process of 10. As a result, R3G3B3
Get the value. The R3G3B3 value is sent to the color display 3 and the color printer 4 and output.

Reference numeral 14 denotes the input of the glossiness of the document. The glossiness of the document is obtained, and a value is input to the glossiness correction processes 11 and 12.

With the above processing, it is possible to perform color correction for correcting deterioration due to the influence of glossiness of a color image document.

(Embodiment 2) Embodiment 2 of the present invention
In the first embodiment of the present invention, the glossiness of a color document used in the glossiness correction of the color scanner is automatically detected.

FIG. 3 is a schematic view showing the principle of measuring glossiness. Reference numeral 15 denotes a light source, which emits light toward the measurement surface. A measurement surface 16 reflects light in this range.
Reference numeral 17 denotes a light receiver for detecting the intensity of reflected light.
The glossiness is determined by the ratio of the intensity of the reflected light measured at the measurement portion to the intensity of the reflected light from the gloss reference plate according to this measurement principle.

FIG. 4 shows a configuration diagram of the color scanner. 1
Reference numeral 8 denotes a color image original, which is set on the scanner with the reading side facing down on the surface of the scanner. A scanner reading unit 19 scans the original 18 while moving left and right. A document reading unit 20 irradiates the document 18 with light and reads reflected light from an image. A light source 21 irradiates the original with light. 22 is a light receiver,
Detect reflected light. Reference numeral 23 denotes a CCD for separating the reflected light into RGB signals.

To detect the glossiness, the glossiness reference plate is read in advance, the light intensity is detected by the light receiver 22, and stored.
When reading an original, the light intensity of light reflected from the original is detected by the light receiver 22 and compared with the stored intensity of the reflected light of the gloss reference plate to detect the gloss of the original.

The detected glossiness is applied to the glossiness correction processing 1 shown in FIG.
By inputting 1 and 12, glossiness correction can be performed.

(Embodiment 3) Embodiment 3 of the present invention
According to the first embodiment of the present invention, a gloss area of a color image document used for gloss correction of a color scanner is designated and set.

FIG. 5 shows an operation window of the scanner driver according to the third embodiment of the present invention.

Reference numeral 24 denotes a window in which the reading conditions of the scanner are set and a reading start button is provided. The window 24 can set the reading resolution of the scanner. Reference numeral 25 denotes a window for displaying the read image, in which a read range is designated by a dotted frame, and the read result is displayed in the frame. Reference numeral 26 denotes a pre-scan start button, which reads the set paper size, reads the image at a reduced resolution, and displays the image on the image display window 25. A scan start button 27 is a button for starting reading only the range selected in the window 25 under the conditions set by the scanner driver. Reference numeral 28 denotes a check box for setting the presence or absence of color adjustment. If the check box is checked, a color adjustment parameter is set, and color adjustment can be performed for scanner reading. Reference numeral 29 denotes a check box for setting whether or not to perform gloss correction processing according to the first embodiment of the present invention. If the check box is checked, gloss processing is performed. Reference numeral 30 denotes a button for calling a screen for setting the glossiness of the glossiness correction.

FIG. 6 shows a window for setting the glossiness. 31 is a setting window. There are three setting conditions. High (Glossy) is set for a document which is coated with vinyl or has high gloss such as a photograph. Medium is set for an original that is not as glossy as a High-setting original. Low is set for a document having no gloss.

By distinguishing the areas of the glossiness set in this way, the presence or absence of gloss is determined from the appearance of the document,
Glossiness can be easily set.

(Embodiment 4) Embodiment 4 of the present invention
Is a configuration in which the glossiness correction processing of the color scanner according to the first embodiment of the present invention, 10, 11, 12, and 13, is performed by a lookup table interpolation method.

FIG. 7 is a schematic diagram of a lookup table interpolation method. Reference numeral 32 denotes an RGB space, which is a cube indicating the range of the entire input color space. This input color space is divided into smaller cubes as shown. The vertex of each cube (Rii, G
ii, Bii), the values (Roi, Goi, Boi) resulting from applying the gloss correction processing 10, 11, 12, 13 in the state 1 of the embodiment of the present invention are stored as a reference table. The reference table is calculated immediately after the glossiness of the document is input.

Reference numeral 33 denotes the coordinate points (r, g, b) of the RGB values after the color correction 9 is performed on the input RGB signals of the color image in the first embodiment.

Numeral 34 denotes a divided cube in the RGB space 32, which is a cube including the input RGB coordinate points 33.

[0055]

(Equation 7)

Each of the input RGB coordinate points 33 and the cube 34
Weights for each vertex (w1, w2,
w3, w4, w5, w6, w7, w8), and values (Roi, Goi, Boi) obtained by performing gloss correction processing on each vertex.
(I = 1 to 8) to obtain an output value RGB (Equation 7).

As described above, the gloss correction processing 10, 1
By performing 1, 12, and 13 by the lookup table interpolation method, high-speed processing can be performed without complicated calculations. Also,
The configuration is such that color correction processing and glossiness correction processing can be easily separated.

(Embodiment 5) Embodiment 5 of the present invention
Is a configuration in which the color correction units of the color scanner unit according to the first embodiment of the present invention are collectively performed using a lookup table interpolation method.

As in the fourth embodiment of the present invention, the processing is performed using a lookup table interpolation method. In the fifth embodiment of the present invention, the color correction process 9 and the glossiness correction processes 10, 11, 12, and 13 of the first embodiment of the present invention are collectively performed by a reference table interpolation method.

A corrected value can be obtained only by performing the lookup table interpolation once, and high-speed processing can be performed as compared with the fourth embodiment.

(Embodiment 6) Embodiment 6 of the present invention
Is a configuration in which the color correction coefficients used in the color correction unit of the color scanner unit according to the first embodiment of the present invention can be easily calibrated by using a color chart having a different glossiness as a document for calibration. is there.

FIG. 8 shows a color chart for calibration used in the sixth embodiment of the present invention. A portion 35 is a gloss determined based on the gloss of the glass plate surface having a refractive index of 1.567 as a reference 100, a portion 35 is a document having a gloss, a portion 36 is a document having a gloss 50, and a portion 37 is provided. Is a document having a gloss level of 90.
The color chart at each gloss level is a color light 3 of red, green, blue, cyan, magenta, and yellow (hereinafter, R, G, B, C, M, and Y).
A gradation pattern from the primary colors and the three printing primary colors to white and black, and a gradation pattern from white to black, that is, a gray scale. The standard value of each color chart, that is, the value measured by the colorimeter, is stored in the storage device as the values of lightness L, chroma C, hue H, and NTSC-RGB.

Hereinafter, the procedure for calibrating the color correction coefficient will be described.
The color charts 35, 36, and 37 are read by a color scanner to obtain respective RGB input signals.

A reference glossiness original is determined. A color correction coefficient used in the color correction processing 9 is obtained from the RGB read value of the scanner of the reference document and the measured RGB value. A color correction process is performed using the scanner RGB read values of the respective color patches with the color correction coefficients previously obtained. Convert RGB values to LCH values. Using the grayscale scanner read value and the L value of the measured value, the change in brightness from higher to lower brightness is obtained by the least square method of the slope AL of (Equation 3) shown in the first embodiment of the present invention. . From the slopes of the gloss levels, the values of the coefficients a and b in (Equation 4) indicating the relationship between the gloss level and the slope AL are obtained by the least square method. By the steps up to here, the coefficient of the glossiness correction of the lightness is obtained.

Using the C value of the scanner read value and the measured value, the change from high to low chroma in each of the RGBCMY hues is represented by the slope AC of (Equation 5) shown in the first embodiment of the present invention. Is obtained by the least squares method. In each RGBCMY hue, the values of A (H) and B (H) in (Equation 6) are obtained from the gradient AC at each glossiness in each hue by the least square method. As described above, the correction coefficients necessary for the color correction processing and the gloss correction processing can be obtained, and the gloss correction coefficient can be calibrated by using an original having a different gloss as a reference color chart for calibration.

[0066]

As is clear from the above embodiment,
ADVANTAGE OF THE INVENTION According to this invention, the color image original with different glossiness can remove the influence of glossiness, and implement | achieve favorable color matching.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a color image input / output device according to a first embodiment of the present invention.

FIG. 2 is a schematic diagram of each process of a color correction process according to the first embodiment.

FIG. 3 is a diagram illustrating the principle of measuring glossiness in the second embodiment.

FIG. 4 is a configuration diagram of scanner reading according to the second embodiment;

FIG. 5 is a view showing a scanner driver parameter setting screen according to the third embodiment;

FIG. 6 is a view showing a setting screen of a glossiness area according to the third embodiment;

FIG. 7 is a conceptual diagram of a lookup table interpolation method according to the fourth embodiment.

FIG. 8 is a diagram showing a form of a color chart for color correction coefficient calibration according to the fourth embodiment.

FIG. 9 is a schematic diagram of each process of a color correction process according to the related art.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Color scanner 2 Computer main body 3 Color display 4 Color printer 11 Brightness gloss correction processing 12 Saturation gloss correction processing 14 Original gloss input section 22 Receiver 30 Gloss correction setting button 31 Gloss area setting screen 38 Color Correction coefficient calibration color chart

Continued on the front page F term (reference) 2C262 AC04 BA03 BA15 BA16 BA18 BA19 BC13 EA08 GA01 5B057 AA11 BA02 CA01 CA08 CA12 CA20 CB01 CB08 CB12 CC01 CE18 DB02 DB06 DB09 DC30 5C077 LL19 MP08 PP25 PP27 PP28 PP31 PP32 PP35 PP41 PP43 SS05 HB06 HB11 HB12 LA01 LA10 LA28 LB01 MA04 MA10 MA17 NA03

Claims (10)

[Claims] An image reading unit for reading an original; a unit for inputting an image signal read by the image reading unit; a unit for converting the image signal into brightness, saturation, and hue of three attributes of color; Means for inputting the glossiness of the document, glossiness correction means for correcting the brightness and the saturation based on the input glossiness, and output of the corrected brightness, saturation and hue to an image output device. A color correction device comprising means for converting an image signal. 2. An image reading means for reading a document, a means for inputting an image signal read by the image reading means, a means for detecting the glossiness of the document, Means for converting into saturation and hue; gloss correction means for correcting the brightness and the saturation based on the detected gloss; and an image for output of the corrected brightness, saturation and hue from an image output device. A color correction device, comprising: means for converting into a signal. 3. Image reading means for reading an original, means for inputting an image signal read by the image reading means, means for specifying a glossy area of the original, Means for converting into saturation and hue, gloss correction means for correcting the brightness and the saturation by the designated gloss area, and means for outputting the corrected brightness, saturation and hue to an image output device. A color correction device comprising means for converting an image signal. 4. An image reading means for reading a document, a means for inputting an image signal read by the image reading means, a means for externally inputting glossiness of the document, and a method for converting the image signal into three attributes of color. Means for converting brightness, saturation, and hue, gloss correction means for correcting the brightness and the saturation based on the input gloss, and an image output device for correcting the corrected brightness, saturation, and hue. A color correction device comprising means for converting an image signal into an output image signal. 5. An image reading means for reading a document, means for inputting an image signal read by the image reading means, means for inputting glossiness of the document, and brightness of three attributes of color, Means for converting into saturation and hue, means for calculating a correction amount of lightness and saturation using the input glossiness, means for creating a reference table, storage means for storing the reference table, Glossiness correction means for correcting the brightness and the saturation using the stored reference table, and means for converting the corrected brightness, the saturation, and the hue into an output image signal of an image output device. Color correction device. 6. A dividing means for dividing an input color space of an arbitrary color image input device into three-dimensional figures, and a color separation component of the color image output device corresponding to each vertex of the solid divided by said dividing means. Setting means for setting each vertex output value, and performing an interpolation process using the vertex output value set by the setting means to obtain an output value to an output device corresponding to the input signal in the input color space In a color correction apparatus including an interpolation unit, the setting unit performs correction of lightness, saturation, and hue, which are three attributes of color, on each vertex of the input color space using glossiness of the document. 5. The color correction apparatus according to claim 1, wherein a vertex output value in the input color space is set. 7. A means for reading a plurality of color patches having a plurality of gloss levels with a color image input device, a means for storing a colorimetric value of the color patch, and a means corresponding to each gloss level and each gloss level. 7. The color correction apparatus according to claim 1, further comprising: means for obtaining a correction coefficient of a glossiness correction means from a read value of the color chart to be read by the color image input device and the colorimetric value. 8. A program product for performing a color correction based on the glossiness of a color image input device which is affected by a color image input signal by the glossiness of a document, and the procedure described in the program includes the following. Inputting the image signal of the original, inputting the glossiness of the original,
Converting the image signal into lightness, saturation, and hue of three attributes of color; correcting the lightness and the saturation by the glossiness; and performing the glossiness correction; the corrected brightness, saturation, and the hue. Is converted into an image signal for output of the image output device. 9. The color correcting apparatus according to claim 1, wherein said original is a monochrome original or a color original. 10. A color correction apparatus according to claim 1, wherein said gloss correction means corrects at least two of brightness, chroma, and hue of said image signal by gloss. .