JP2003008913A - Image processor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image processor for reducing the color component of a background of an image that can reduce the color component of the background of an original and reproduce the light color of the original. SOLUTION: A color space conversion section 110 of a background processing section 100 converts image data in an RGB color space into image data L*(1), a*(1) and b*(1) expressed in an L*, a*, b* color space. A lightness conversion section 120 converts the image data in the RGB color space into the image data with greater lightness when the lightness L*(1) is a 1st threshold value L1 or more. A color compression section 130 with a saturation conversion section 132 and a color space conversion section 134 converts the image data in the RGB color space into the image data with smaller saturation of the color image when the lightness L*(2) is a 2nd threshold value L*max greater than the 1st threshold value L1 or more. That is, the saturation conversion section 132 converts the data into data with zero saturation when the lightness L*(2) is the L*max or more, and a color space conversion section 134 uses a*(3), b*(3), L*(3) to convert data in a color space data for pre-processing into data in an output color space.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image processing apparatus for handling an image, such as a display device, a copying machine, a FAX, or a scanner. In particular, it relates to the removal of the background color of the background portion of a color document.

[0002]

2. Description of the Related Art Image processing devices such as display devices, copying machines, fax machines, and scanners that handle images are known. Here, for example, if a document image is read by a scanner and the read multi-valued image is output by a display or a printer, the shade of the background of the document is also reproduced,
The background image is smeared in the output image. When the original is a color image, a so-called "fog" phenomenon occurs in which the background color is not white.

As a method for solving this problem, a background removal method has been proposed which removes stains on the background of an original before outputting an image. For example, the method described in Japanese Patent Laid-Open No. 6-197216 uses an input color image signal as a lightness, saturation,
After conversion into a signal on the color space representing the hue and the hue, the background color is removed by reducing the density of white or a color signal close to white according to the lightness and the saturation.

In the first embodiment of Japanese Patent Laid-Open No. 6-197216, the input color image signal in the RGB color space is converted into a signal in the L * u * v * color space (this conversion is preprocessed. After the color conversion), the lightness L * of the color component of the white background or the highlight having a high lightness L * is made higher, while the values of u * and v * are used as they are, in the output color space. A method has been proposed in which a color reproduction area in a high lightness area is extended by converting the signal into a signal (this conversion is called a color conversion for output), and thereby a background color is removed. Further, it has been proposed to round the signal value so that it will fit in the color space when overflow or underflow occurs during color conversion for output.

[0005]

However, the method described in Japanese Patent Laid-Open No. 6-197216 reduces the density of a white or near-white color signal according to the converted lightness and saturation. It is necessary to calculate the saturation and to reflect the calculated saturation in the density conversion, but no specific method is specified.

On the other hand, in the output color conversion, if the signal value is rounded so that overflow or underflow does not occur, the area of high lightness does not become white depending on the result of the output color conversion and the color component Will remain. In this way, if the tint remains without outputting the background color of the original as white, for example, in copying, when the output original is copied again, the influence of "fog" remains. Color components can be removed by increasing the degree of density conversion, but this causes a new problem that the light color (highlight color) of the original that is not erased is not faithfully reproduced.

Further, in the method described in Japanese Patent Laid-Open No. 6-197216, since the saturation is not changed according to the lightness conversion, the light color (highlight color) of the original is not faithfully reproduced.

The present invention has been made in view of the above circumstances, and provides an image processing apparatus capable of surely reducing the background color component of an original and reproducing the light color of the original. With the goal.

[0009]

That is, an image processing apparatus according to the present invention is an image processing apparatus for reducing a color component of a background portion of an image, in which an image signal carrying an image is converted into a lightness signal and a chromaticity signal. A color space conversion unit for pre-processing for converting to a signal,
When the lightness represented by the lightness signal converted by the preprocessing color space conversion unit is equal to or greater than a predetermined value (first threshold value),
A brightness conversion unit that converts the brightness signal so that the brightness becomes larger, and the brightness represented by the brightness signal has a predetermined value (first
A second threshold value larger than the threshold value of 1) or more, a color compression unit that converts the chromaticity signal so that the saturation represented by the chromaticity signal becomes smaller.

[0010]

In the image processing apparatus having the above structure, first, the lightness conversion unit converts the image converted by the preprocessing color space conversion unit so that the lightness becomes higher when the lightness is equal to or higher than the first threshold value. . As a result, the color gamut in the highlight part, where the brightness is equal to or higher than the first threshold value, is expanded, and the background color component is suppressed.

The color compressing unit converts the brightness of the image to be smaller when the brightness converted by the brightness converting unit is equal to or higher than the second threshold value. As a result, the highlight color whose brightness is between the first threshold value and the second threshold value is reproduced with high fidelity, and the color component in the highlight portion whose brightness is equal to or higher than the second threshold value is suppressed. It

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a mechanism diagram of an example of a color copying machine equipped with an embodiment of an image processing apparatus of the present invention. This color copying machine includes an image acquisition section (image reading section, image input section) 10, an image processing section 20 which is an example of an image processing apparatus of the present invention, an image output section (image recording section) 30, a user interface 50, and An edit pad 60 is provided.

The image acquisition unit 10 reads an input image obtained by reading a document placed on the platen glass 11 with red, green,
Convert to digital image data of each color component of blue. For example, light from a light source 12 having a halogen lamp irradiates a document placed on the platen glass 11, and counter light is split into red, green, and blue colors through an optical system (not shown).
Then, each color light is divided for each color light, for example, CC
It is incident on a line sensor (image sensor) 13 including a D (solid-state image sensor), and an input image is, for example, 400 dpi.
By reading at a resolution of (400 dots / 1 inch), analog image signals of red, green, and blue color components can be obtained. Further, in the signal processing unit 14, an amplification unit (not shown) amplifies each red, green, and blue image signal from the line sensor 13 to a predetermined level, and an A / D converter (not shown) converts the signal into digital data. , Red, green, blue digital image data R, G, B are A /
Obtained from the D converter. The red, green, and blue image data R, G, B are sent to the image processing unit 20 via the cable 15.
Sent to.

At the time of this reading, the light from the light source 12 irradiates the entire surface of the original document, and the line sensor 13 reads the input image over the entire surface. The optical system including the light source 12, the line sensor 13 and the signal processing. Part 14 is arrow 1
As shown by 6, it is moved from the left side to the right side in FIG.

The image processing unit 20 is based on the red, green, and blue image data R, G, and B from the signal processing unit 14 of the image acquisition unit 10, and is black (K), yellow (Y), magenta (M). ), A cyan (C) on / off binary toner signal is obtained, and each toner signal is output to the image output unit 30.

The image output section 30 of the present embodiment has image forming sections 31K, 31Y, 31M and 31C of K, Y, M and C, which are arranged in parallel in one direction at regular intervals. The leading edge detector 44 is provided in proximity to the conveyance path of the sheet conveyed from the sheet cassette 41 to each image forming unit. The leading edge detector 44 optically detects the leading edge of the sheet sent onto the transfer belt 43 from the sheet cassette 41 through the registration rollers 42 to obtain a leading edge detection signal, and the leading edge detection signal is sent to the image processing section 20. send.
The image processing unit 20 can sequentially obtain on / off binarized toner signals of K, Y, M, and C colors at regular intervals in synchronization with the input leading edge detection signal.

In the image output unit 30, first, the semiconductor laser 38K is driven by the black on / off binary toner signal from the image processing unit 20 to convert the black on / off binary toner signal into an optical signal. Then
The converted laser light is emitted toward the polygon mirror 39. This laser light is further reflected by the reflection mirror 47K,
An electrostatic latent image is formed on the photoconductor drum 32K by scanning the photoconductor drum 32K charged by the primary charger 33K via 48K and 49K. This electrostatic latent image is made into a toner image by the developing device 34K to which black toner is supplied, and this toner image is transferred to the transfer belt 43.
While the upper sheet passes through the photoconductor drum 32K, it is transferred onto the sheet by the transfer charger 35K. After the transfer, the cleaner 36K removes excess toner from the photosensitive drum 32K.

Similarly, the semiconductor lasers 38Y, 38M, 3
8C is driven by on / off binary toner signals of corresponding colors Y, M, and C, which are sequentially obtained from the image processing unit 20 at regular intervals with respect to the black on / off binary toner signal. The on / off binary toner signal of each color is converted into an optical signal, and the converted laser light is directed toward the polygon mirror 39. This laser light
Furthermore, the reflection mirrors 47Y to 49Y, 47M to 49M, 4
Primary charger 33Y, 33M, 33 via 7C-49C
By scanning the photosensitive drum 32K charged by C, electrostatic latent images are sequentially formed on the photosensitive drums 32Y, 32M, and 32C. The electrostatic latent images are sequentially made into toner images by the developing devices 34Y, 34M, and 34C to which the toners of the respective colors are supplied. Transfer chargers 35Y, 35M, 35 corresponding to the passing through
It is sequentially transferred onto the paper by C.

The sheet on which the toner images of K, Y, M, and C are sequentially transferred in this manner is separated from the transfer belt 43, the toner is fixed by the fixing roller 45, and the toner is fixed to the outside of the copying machine. Is discharged.

The user interface 50 is used by the user to select a desired function and instruct execution thereof. In this example, the user interface 50 includes a color CRT display 51 and a hard control panel 52, and an infrared touch board 53 is further combined. Then, the soft buttons on the screen can be used to directly specify the conditions. The edit pad 60 can thereby set the area to be edited.

FIG. 2 is an image processing section 2 which is an example of the image processing apparatus of the present invention, which is provided in the color copying machine having the above construction.
3 is a block diagram of the first embodiment of No. 0. FIG. In the image processing unit 20, the red, green, and blue image data R, G, and B from the image acquisition unit 10 are temporarily stored in the page memory 62, and color correction is performed by the pre-stage color correction processing unit 62. After that, it is input to the background processing unit 100. Base processing unit 100
Is the lightness signal L * of the uniform color space for the image data R, G, B.
In addition, the lightness signal L * and the chromaticity signals a * and b *, which are divided into the chromaticity signals a * and b * representing the saturation and the hue, are converted into, and the converted lightness signal L * and chromaticity signals a * and b * are yellow (Y) and magenta (M). , Cyan (C), and black (K) image data. At this time, the background processing unit 100 sets K,
The image data of each color of Y, M and C is subjected to background removal processing according to the background density of the input image.

The background processing unit 100, which is a main part of the image processing unit 20 of the first embodiment, is an RGB unit that carries a color image.
Image data on the color space is converted into data L * (1), a * on the color space for preprocessing, which represents lightness, saturation, and hue.
(1), b * (1) pre-processing color space conversion unit 110, and when the lightness L * (1) of the converted color image is equal to or greater than the first threshold value L1, the lightness becomes larger. And a lightness conversion unit 120 for performing the above conversion. Further, the background processing unit 100 uses the second threshold value L in which the lightness L * (2) converted by the lightness conversion unit 120 is larger than the first threshold value L1.
When it is equal to or more than * max, the color compression unit 130 is provided to convert the color image so that the color image becomes less saturated.

When the lightness L * (2) converted by the lightness conversion unit 120 is greater than or equal to the second threshold L * max, the color compression unit 130 makes the saturation of the color image substantially zero (“0”). And a saturation conversion unit 132 for converting
Chromaticity signal a * (3) representing the chroma converted by 32,
b * (3) and the lightness L * (2) (= L * (3)) converted by the lightness conversion unit 120, the color for preprocessing converted by the color space conversion unit 110 for preprocessing An output color space conversion unit 134 for converting the data in the space into the data in the output color space different from the preprocessing color space.

The color space for preprocessing may be any color space that can represent a color image by distinguishing lightness and saturation (more preferably also hue), and L * a *
The color space is not limited to the b * color space, and may be a uniform color space such as L * u * v *. On the other hand, the output color space may be a color space corresponding to an output unit connected to the subsequent stage of the image processing unit 20, and for example, when outputting an image on a display, an RGB color space or a color printer is used. The YMC color space may be used when outputting the image. In this embodiment, the YMC
Use color space.

The image area detecting section 75a includes a color space converting section 110.
Based on the lightness signal L * and the chromaticity signals a * and b * from, the character portion and the picture portion of the input image are identified in units of 8 × 8 pixel blocks, for example, in the area identified as the character portion, “ Binary data which becomes "1" and becomes "0" in the area identified as the picture portion is obtained as an image area signal. The enlargement / reduction unit 75b reduces or enlarges this image area signal in the main scanning direction which is the line direction of the line sensor 13 by simple thinning or simple enlargement (both reduction and enlargement are collectively referred to as scaling).

The enlarging / reducing unit 76 further includes a color space converting unit 134.
Image data, which is multi-valued data of each color of Y, M, C, and K from, is scaled in the main scanning direction by interpolation between two points,
The smoothing processing unit 77 uses the smoothing spatial filter to smooth the image data of each color of Y, M, C, and K scaled by the scaling unit 76 according to the image area signal from the scaling unit 75b. .

The smoothing spatial filter of the smoothing processing unit 77 is
It removes moire and smoothes halftone data.
The coefficient by which the image data is multiplied is switched in real time according to the image area signal which is the binary data from the expansion / contraction unit 75b. For example, when the spatial filter for smoothing has a kernel size of 3 × 3, the smoothing processing unit 77 removes moire by setting the image area signal to “1” in the area identified as the character portion of the input image. On the other hand, the filter constant is switched to a target low-pass filter constant, while in the area identified as the pattern portion of the input image, the image area signal is set to "0" to switch to a filter constant having a tight smoothing characteristic.

Next, the encoding unit 81 performs the orthogonal transform encoding such as DCT (Discrete Cosine Transform) or the vector quantization on the image data of each color of K, Y, M and C smoothed by the smoothing processing unit 77. And then lossy compression is performed. After that, the writing unit 83 causes the encoding unit 8 to
The encoded image data of each color of K, Y, M, and C that has been irreversibly compressed by 1 is an image memory 8 that is an example of an image storage unit.
The writing section 85 writes the binary data from the enlarging / reducing section 75b into the image area memory 84 which is prepared for a total of four planes for each color of K, Y, M, and C as well as the image memory 82. Write a certain image area signal at the same time.

Then, in synchronization with the leading edge detection signal from the leading edge detector 44 of the image output section 30, the reading section 86 sequentially outputs the coded image data of each color of K, Y, M and C from the image memory 82 at regular intervals. The reading section 88
However, the image area signals of the same contents for K, Y, M, and C are sequentially read out from the image area memory 84 at regular intervals. The decoding unit 89 decodes the coded image data of each color of K, Y, M, and C, which are sequentially read from the image memory 82 at regular intervals, and restore the original image data.

The edge enhancement unit 91 provided in the enhancement processing unit 90 uses the spatial filter for edge enhancement to read K, Y, and S sequentially read from the image area memory 84 at regular intervals.
According to the image area signals of the same contents for each of M and C, K, Y, which are sequentially read from the decoding unit 89 at regular intervals.
The edge enhancement processing is performed on the decoded image data of each color of M and C.

The gamma correction unit 92 provided at the subsequent stage of the edge emphasizing unit 91 outputs the image data of each color of K, Y, M, and C which has been subjected to the edge emphasizing process and is sequentially obtained from the edge emphasizing unit 91 at regular intervals. Gamma correction is performed according to the image area signals of the same contents for K, Y, M, and C, which are sequentially read from the image area memory 84 at fixed intervals.

Although not shown, the image processing unit 20
, The image data of each color of K, Y, M, and C obtained sequentially from the gamma correction unit 92 at fixed intervals is D / A.
It is converted into a process color gradation toner signal, and the process color gradation toner signal is binarized to turn on / off 2
It is converted into a binarized toner signal, and the on / off binarized toner signal is output to the image output unit 30 as described above.

The edge enhancement spatial filter of the edge enhancement unit 91 switches the coefficient by which the image data is multiplied in real time according to the image area signal which is the binary data read from the image area memory 84. For example, when the spatial filter for edge enhancement has a kernel size of 5 × 7, the edge enhancement unit 91 sets the image region signal to “1” in the region identified as the character portion of the input image, thereby enhancing the enhancement characteristic. On the other hand, in the area identified as the picture portion of the input image, the coefficient is changed to a coefficient having a plain characteristic by setting the image area signal to “0”.

The gamma correction unit 92 has, for example, two types of non-linear lookup tables, and switches the input / output characteristics in real time according to the image area signal which is binary data read from the image area memory 84. For example, the gamma correction unit 92 switches to the input / output characteristic of the high gamma curve having the edge enhancement characteristic when the image area signal is set to “1” in the area identified as the character portion of the input image,
In the area identified as the picture portion of the input image, the input / output characteristic of the smooth gamma curve is switched so that faithful gradation reproduction is performed by setting the image area signal to "0".

The above-mentioned example is a spatial filter for smoothing,
Although the edge enhancement spatial filter and the gamma correction unit 92 have the same characteristics for each color of Y, M, C or K, Y, M, C, even if the characteristics are changed so as to have optimum characteristics for each color. Good.

Further, the image output section 30 uses K, Y, M, and K on one photoconductor drum by one laser light scanner.
An electrostatic latent image of each color of C is sequentially formed, and the electrostatic latent image is sequentially formed by a developing device provided around the photosensitive drum and supplied with toners of each color of K, Y, M, and C, respectively. Alternatively, the toner images may be sequentially and multiple-transferred onto the sheet adsorbed on the transfer drum.

FIG. 3 shows an outline of data conversion in the background processing section which is a main part of the image processing section of the first embodiment.
When the color image data (RGB data) represented in the RGB color space is input, the color space conversion unit 110 converts the RGB data for each pixel into data L * a * b * data L * in the color space.
(1), a * (1), b * (1). Since the color conversion method in the color space conversion unit 110 is known, detailed description thereof will be omitted. Next, the brightness conversion unit 120
When the value L * (1) of the lightness component is equal to or larger than the first threshold value L1, the lightness is converted to be larger. That is, in the conversion of the lightness component, the lightness of the color component of the white background or the highlight having a high lightness equal to or higher than the first threshold L1 is made higher. As a result, the color gamut in the high lightness range in which the lightness is equal to or higher than the first threshold value L1 is extended, so that the background color component is suppressed by further increasing the lightness in the input near the highlight part.

The color compressing section 130 also includes a lightness converting section 120.
The lightness L * (2) converted by the second threshold L * ma
When the value is equal to or more than x (threshold L2 larger than the first threshold L1 on the L * (1) axis), the conversion is performed so that the saturation becomes smaller. At this time, the color compression unit 130 preferably reduces the saturation so that the hue does not change. Specifically, the saturation conversion unit 132 causes the brightness level L * after the brightness conversion.
When (2) is greater than or equal to the second threshold L * max, the saturation is forcibly converted to approximately “0”, that is, a * (3) = b * (3) ≈0. Then, the color space conversion unit 134
Saturation a * (3), b * (3) and lightness L * after conversion
(3) (= L * (2)) is used to convert to data YMCK in the YMC color space. Since the color conversion method in the color space conversion unit 134 is known, its detailed description is omitted.

As a result, when the lightness level L * (2) is from the first threshold value L1 to the second threshold value L * max, the values of the chromaticity signals representing the saturation and the hue are a1 and b1, respectively.
Since linearity is maintained between ~ a2 and b2, the color reproducibility is not impaired, and the lightness L * (1) is from the first threshold L1 to the threshold L2 corresponding to the second threshold L * max. While the highlight color that is between is reproduced almost faithfully, the threshold L
A color component of a highlight portion is suppressed more reliably than 2 or more.

Here, in the color space conversion processing in the color space conversion unit 134, the data on the L * a * b * space is converted to Y.
When converted to data in the MCK color space, generally, when the input has no saturation, the value of each YMCK becomes "0", that is, white, so that it is not affected by the subsequent color space conversion processing. In addition, it is possible to output white after the background color is removed, and “fog” does not occur in the print output.
On the other hand, the brightness level L * (2) changes from the first threshold value L1 to the second threshold value L2.
Up to the threshold value L * max of, the linearity of each value of YMCK is maintained, so that the color reproducibility is not impaired. On the other hand, at this time, since the background color removal processing is performed by the brightness conversion unit 120 only on the brightness components having the first threshold value L1 or more, the background color of the background of the document is suppressed (blown out), and the background color is suppressed. The color becomes less noticeable.

Further, the image processing unit 20 of the first embodiment described above.
In the above, since the target of the background removal processing is limited to the white background with high lightness and the highlight portion with low saturation, there is no change in color tone in the low lightness area, and the background removal processing is performed in the high lightness area. However, the processing is excellent in color reproducibility without changing the hue.

FIG. 4 is a block diagram of a second embodiment of the background processing section which is the main part of the image processing apparatus of the present invention. The background processing unit 100 of the second embodiment is different from the first embodiment in the configuration of the color compression unit 130. That is, the color compressing unit 130 of the second embodiment converts the data in the preprocessing color space converted by the color space converting unit 110 into the data in the output color space, and the lightness converting unit 120. When the brightness L * (2) is equal to or larger than the second threshold value L * max, the color space conversion unit 136 that makes the value of the data on the output color space substantially zero is included.

FIG. 5 shows the background processing section 100 of the second embodiment.
The outline of the data conversion in is shown. The color space conversion unit 136 in the color compression unit 130 uses the data L * (2), a expressed in the L * a * b * color space that represents the lightness, the saturation, and the hue.
When * (1) and b * (1) are input, first, for each pixel, data Y (1), M (1), C (1) on the YMC color space as a color space according to the output. , K (1). Next, the color space conversion unit 136 causes the lightness conversion unit 120.
When the value L * (2) of the lightness component converted by is greater than or equal to the second threshold value L * max, all the data values (color conversion output values) in the YMC color space are forced to be more than the converted values. It is made smaller (preferably approximately zero). As a result, as in the case of the first embodiment, the color component in the highlighted portion is surely suppressed when the lightness level L * (2) is not less than the second threshold value L * max.

On the other hand, as in the first embodiment, the lightness level L * (2) changes from the first threshold value L1 to the second threshold value L * max.
Up to, the values of YMCK are Y1, M1,
Since the linearity is maintained among C1, K1 to Y2, M2, C2, and K2, the color reproducibility is not impaired, and at this time, the lightness conversion unit 120 allows only the lightness component equal to or higher than the first threshold L1. Since the background color removal processing has been applied to
The background color of the background of the original is suppressed (blown), and the background color becomes inconspicuous.

Although the present invention has been described using the embodiments, the technical scope of the present invention is not limited to the scope described in the above embodiments. Various changes or improvements can be added to the above-described embodiment, and a mode in which such changes or improvements are added is also included in the technical scope of the present invention. Also,
The above embodiments do not limit the claimed invention, and all combinations of the features described in the embodiments are not necessarily essential to the solution of the invention.

[0047]

As described above, according to the present invention, it is possible to surely reduce the background color component of the document in the highlight portion and to reproduce the light color of the document.

[Brief description of drawings]

FIG. 1 is a mechanism diagram of an example of a color copying machine equipped with an example of an image processing apparatus of the present invention.

FIG. 2 is a block diagram of a first embodiment of an image processing unit of the present invention.

FIG. 3 is a diagram showing an outline of data conversion in a background processing unit of the first embodiment.

FIG. 4 is a block diagram of a second embodiment of a background processing unit that is a main part of the image processing apparatus of the present invention.

FIG. 5 is a diagram showing an outline of data conversion in a background processing unit of the second embodiment.

[Explanation of symbols]

20 ... Image processing unit, 100 ... Background processing unit, 110 ... Color space conversion unit, 120 ... Lightness conversion unit, 130 ... Color compression unit, 1
32 ... Saturation conversion unit, 134 ... Color space conversion unit, 136 ... Color space conversion unit, L1 ... First threshold value, L * max ... Second threshold value

Continued front page    F-term (reference) 2C262 AA24 AB13 BA16 BA19 BC07                       BC19 DA17                 5B057 CA01 CA08 CA12 CB01 CB08                       CB12 CE17 CE18 CH11 DB02                       DB06 DB09 DC25                 5C077 LL19 MP08 PP33 PP35 PP36                       PP37 PP52 PQ22 RR14 TT06                 5C079 HB03 HB06 HB08 HB12 LA07                       LA26 LB02 MA02 NA03 NA07                       PA01 PA02 PA05

Claims (3)

[Claims] 1. An image processing apparatus for reducing a color component of a background portion of an image, comprising: a color space conversion unit for pre-processing for converting an image signal carrying the image into a lightness signal and a chromaticity signal; A lightness conversion unit that converts the lightness signal so that the lightness becomes larger when the lightness represented by the lightness signal converted by the preprocessing color space conversion unit is equal to or greater than a first threshold; and the lightness signal. And a color compression unit that converts the chromaticity signal so that the saturation represented by the chromaticity signal becomes smaller when the lightness represented by is greater than or equal to a second threshold value that is greater than the first threshold value. Image processing device. 2. The saturation which converts the chromaticity signal so that the saturation shown by the chromaticity signal becomes smaller when the brightness represented by the brightness signal is equal to or higher than the second threshold value. Using a conversion unit, the saturation signal converted by the saturation conversion unit and the brightness signal converted by the brightness conversion unit,
An output color that converts the signal on the preprocessing color space converted by the preprocessing color space conversion unit into a signal on an output color space different from the preprocessing color space. The image processing apparatus according to claim 1, further comprising a space conversion unit. 3. The color compression unit outputs the signal on the preprocessing color space converted by the preprocessing color space conversion unit to an output color different from the preprocessing color space. When the lightness represented by the lightness signal is equal to or greater than the second threshold value, the output signal is converted into a signal on a space so that the saturation represented by the signal on the output color space becomes smaller. The image processing apparatus according to claim 1, further comprising an output color space conversion unit that converts a signal on the color space of.