JPH08214175A - Image processing method - Google Patents

Abstract

PURPOSE: To improve the color reproducibility by simply correcting a color reproduction range being a reference of color matching processing corresponding to a difference from image output devices or a change in the color reproduction range due to secular deterioration. CONSTITUTION: In the image processing unit applying conversion processing to image data received by an image input device in matching with a characteristic of an image output device 12, a color reproduction range correction device 8 correcting a processing result of a color reproduction range calculation section 6 to calculate a color reproduction range of an image output device 12 is provided in a gamut compression processing section 15 applying gamut compression processing to the received image data so as to be in matching with the color reproduction range of the image output device.

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 processing color information, and more particularly to an image processing apparatus for performing color matching processing on input image data so as to match a color reproduction range of an output device.

[0002]

As is well known, in an image processing system such as a network printing system which is composed of image input / output devices having different characteristics such as a CRT display, an image scanner and a printer, color reproduction between the respective devices. The difference in range is a problem.
In order to solve this problem, conventionally, when performing color matching processing between image input / output devices having different characteristics, three-dimensional color matching between devices having different color reproduction ranges is performed for the purpose of faithful color reproduction. It is realized by linear or nonlinear mapping of space, and such a technique is called gamut compression.

As one element for realizing the gamut compression technique, there is a color reproduction range determination process, and several systems have been proposed conventionally. For example, JP-A-4-400
In No. 72, the maximum reproducible saturation corresponding to the brightness and chromaticity of the output device is set to a two-dimensional LUT (Look Up Table).
The maximum saturation corresponding to the lightness and chromaticity of the input color signal is obtained from this table, and the maximum saturation and the saturation of the input color signal are compared to determine the color of the input signal. A method is adopted to judge whether or not it is within the reproduction range.

Further, in Japanese Patent Laid-Open No. 4-181870, the color reproduction range corresponding to the brightness, chromaticity and saturation of the output device is stored as a flag value in a three-dimensional LUT, and the brightness of the input color signal is stored. A method is adopted in which flag values corresponding to chromaticity and saturation are obtained from this table and whether or not the input signal is within the color reproduction range is determined based on this.

[0005]

However, in the above-mentioned conventional techniques, the contents of the storage table for storing the color reproduction range depend on the output device.
In addition, since it is fixed in the initial setting state, it is impossible to avoid erroneous judgments caused by changes in the color reproduction range due to differences in output devices due to machine bodies, deterioration over time, etc. There was a problem that erroneous determination due to the above cannot be avoided.

Further, in order to correct the error which causes the above-mentioned erroneous determination, it is necessary to rewrite the contents of the storage table, but the storage table covers the color space that the input color signal may have. However, if the capacity of the memory table is increased to improve color reproducibility, it will take a lot of time and effort to create the table and rewrite the memory contents accordingly. There was also.

The present invention has been made under such a background, and a color reproduction range as a reference of color matching processing can be simply provided in response to a change in the color reproduction range due to a machine difference of an image output apparatus or deterioration over time. It is an object of the present invention to provide an image processing apparatus that can correct the color and improve color reproducibility. Another object of the present invention is to improve the color reproducibility by correcting the color reproduction range corresponding to the characteristics of the input image data.

[0008]

In order to solve the above-mentioned problems, the invention according to claim 1 provides an image processing apparatus for converting input image data so as to match the characteristics of a predetermined image output apparatus. Storage means for storing characteristic information corresponding to the color reproduction range of the image output device, and color matching processing for the image data based on the characteristic information so as to match the color reproduction range of the image output device. It is characterized by comprising a converting means and a correcting means for correcting a color reproduction range which is a reference of the color matching processing by the converting means.

According to a second aspect of the invention, in the first aspect of the invention, the correction amount by the correction means is updated according to the elapsed time or the number of image outputs.

According to a third aspect of the invention, in the first aspect of the invention, the correction amount by the correction means is determined according to the characteristics of the image data.

[0011]

According to the present invention, the storage means stores characteristic information corresponding to the color reproduction range of the image output device,
Based on this characteristic information, the conversion means performs color matching processing on the input image data so as to match the color reproduction range of the image output device, and the correction means uses the color that serves as a reference for the color matching processing by the conversion means. Correct the reproduction range. As a result, it is possible to easily eliminate an error in the color matching process due to various causes such as machine differences without the work of changing the content of the characteristic information.

According to the second aspect of the invention, it is possible to eliminate an error in the color matching process due to deterioration over time.

According to the third aspect of the invention, it is possible to make a correction corresponding to the characteristics of the input image data.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. In the following embodiments, it is assumed that the present invention is applied to an image processing device such as a digital color copying machine.

A: First Embodiment (1) Overall Structure of Embodiment FIG. 1 is a block diagram showing the overall structure of an image processing apparatus according to the first embodiment of the present invention. In the figure, 1 is an image input device such as an image scanner (hereinafter referred to as an input device), 2 is a color space conversion for mutually converting a color space specific to the input device and a color space used inside the image processing device. Reference numeral 3 denotes an input color signal chromaticity conversion unit, 4 denotes an input color signal saturation conversion unit, 5 denotes a lightness compression processing unit, 9 denotes a saturation compression processing unit, and 10 denotes an output device-specific color space to be described later. A color space conversion unit for mutually converting the color space used in the image processing apparatus, 11 is a black plate generation / UCR processing unit, 12
Is an image output device such as a printer (hereinafter referred to as an output device). A gamut compression processing unit 15 is configured by the color reproduction range calculation units 6 and 7, the color reproduction range correction mechanism 8, the saturation compression processing unit 9, and the brightness compression processing unit 5.

(2) Overall Operation of Embodiment Next, the overall operation of the embodiment having the above configuration will be described. First, the input device 1 reads the image of the document,
It outputs R (red), G (green), and B (blue) color signals corresponding to the input image. The R, G, B signals are L ^* , a ^* , b ^* which are the internal color spaces of the device in the color space conversion unit 2 ^.
Converted to a signal. Then, the a ^* and b ^* signals are converted into chromaticity and saturation through the chromaticity conversion unit 3 and the saturation conversion unit 4 and then input to the gamut compression processing unit 15, where the L ^* signal (brightness) is input. Is directly input to the gamut compression processing unit 15. The chromaticity signal is also input to the chromaticity converter 10.

Next, in the gamut compression processing unit 15, the color reproduction range calculation unit 6 causes the output device 12 corresponding to the chromaticity and the lightness (and the saturation if necessary) of the input color signal.
The color reproduction range (that is, the maximum saturation) is calculated. Similarly, the color reproduction range calculation unit 7 obtains the color reproduction range of the input device 1 corresponding to the lightness and the chromaticity. Then, the color reproduction range correction mechanism 8 corrects the color reproduction range of the output device 12 calculated by the color reproduction range calculation unit 6. The correction of the color reproduction range is performed in order to compensate for errors due to deterioration of the device over time, differences between machine bodies, and the like, and details thereof will be described later.

Further, the saturation signal is corrected in the gamut compression processing unit 15 to the above-described corrected maximum saturation (corrected color reproduction range of the output device 12) and the input device 1.
It is input to the saturation compression processing unit 9 together with the color reproduction range of and is compression-mapped. Further, the brightness signal is compression-mapped by the brightness compression processing unit 5 in the gamut compression processing unit 15.

The saturation and lightness thus gamut-compressed are supplied to the color space conversion unit 10 together with the chromaticity output from the chromaticity conversion unit 3, and Y (yellow), M (magenta), and C (cyan). It is converted into a three-color density signal. Then, it is sent to the black plate generation / UCR processing unit 11, a signal for one recording color is calculated, and printed by the output device (printer) 12.

(3) Details of Each Section Next, details of each section constituting the gamut compression processing section 15 will be described. Color Reproduction Range Calculation Units 6 and 7 First, details of the color reproduction range calculation units 6 and 7 will be described. The color reproduction range calculation units 6 and 7 have the same configuration except the contents of the color reproduction range storage table.

FIG. 2 is a block diagram showing a configuration example of the color reproduction range calculation unit 6 (or 7) using a two-dimensional LUT. In this figure, 21 is 2 from the upper bits of each of the input signals of lightness and chromaticity (and saturation if necessary).
An address decoder that calculates the address of the dimensional LUT, 2
Reference numeral 2 is a color reproduction range storage table configured by a two-dimensional LUT, 23 is an interpolation coefficient calculation unit that calculates an interpolation coefficient from the lower bits of each of the lightness and chromaticity input signals, and 24-27.
Is a multiplier and 28 is an adder.

The contents of the color reproduction range storage table 22 will now be described with reference to FIG. As shown in FIG. 3A, the maximum reproducible saturation C _11max is defined by the chromaticity H ₁ and the lightness V ₁ , and this maximum saturation C _11max is the output device 12 (in the color reproduction range calculation unit 7, The color reproduction range information of the input device 1) is stored in the color reproduction range storage table 22. For example, as shown in FIG.
Every 10.0 in the range of 1, and the chromaticity is 1 in the range of 360 °.
When the corresponding maximum saturation is set every 0 °, 10 × 3
The color reproduction range is represented by 6 = 360 maximum saturations, and the color reproduction range storage table 22 is a two-dimensional LUT with maximum saturation using lightness and chromaticity as keys.

The color reproduction range storage table 22 must have a capacity capable of storing 2 ⁸ × 2 ⁸ = 65536 types of data, assuming that the input signals of lightness and chromaticity each have an 8-bit width. Actually, in order to avoid an increase in the table capacity, only the representative points of the upper m bits of the input data of lightness and chromaticity are stored, and the color reproduction range is obtained by the interpolation processing using the lower n bits of data. It has become. Here, if the bit width of the input signal is 1 (L) bits, then 1 = m + n. It is desirable that the data stored in the color reproduction range storage table 22 have the same saturation, the same range, and the same bit width as those used in the image processing apparatus.

In this way, the highest m bits of the input signal are used as a key to refer to the color reproduction range storage table 22 and the maximum saturation C _{11max to} C _22max at each representative point is output. In addition,
In this case, the capacity of the table is 2 ^m × 2 ^m × saturation bit width. On the other hand, the interpolation coefficient calculation unit 23 calculates the interpolation coefficients S _{11 to} S ₂₂ from the lower n bits of the input signal. Then, the multipliers 24 to 27 multiply the maximum saturation C _{11max to} C _22max and the interpolation coefficients S _{11 to} S ₂₂ and the adder 28 adds them to obtain a color reproduction range for the input signal. Becomes

Further, referring to FIG. 4, a method of interpolation processing using the two-dimensional LUT by the color reproduction range calculation units 6 and 7 will be described. In FIG. 4, the brightness and chromaticity of the input color signal are represented by (V
_P, when the H _P), 4 single representative points from the upper m bits _{(V 1, H 1),} (V 2, H 1), (V 1, H 2), (V 2,
H ₂ ), and the color reproduction range storage table 22 is searched to obtain the color reproduction range C at each representative point.
_{Calculate 11max} to _C22max . Then, the lower n bits of the (V _P, H _P), dividing the rectangular region surrounded by the representative points into four rectangular areas, and outputs the respective areas S ₁₁ to S ₂₂ as the interpolation coefficient. Here, the areas S _{11 to} S ₂₂ are calculated assuming that the area of the rectangular region surrounded by the representative points is 1. That is, the color reproduction range C _pmax for (V _P , H _P ) is given by the following equation (1). C _pmax = C _11max × S ₂₂ + C _12max × S ₂₁ + C _21max × S ₁₂ + C _22max × S ₁₁ (1)

Although an example using a two-dimensional LUT has been shown here, it is also possible to expand using a three-dimensional LUT as shown in FIG. In addition, the LUT has RAM and R
A semiconductor memory such as an OM is suitable, and it is more desirable if it has a rewritable structure from the outside. Furthermore, (V _P ,
If it is possible to have a table capacity that can cover all combinations of H _P ), the interpolation coefficient calculation unit 23 can be omitted.

The algorithm for calculating the interpolation coefficient is not limited to the above example, and other known algorithms may be used. Further, the interpolation coefficient calculation unit 23 and the color reproduction range storage table 22 may be configured by software to obtain the color reproduction range.

Color Reproduction Range Correction Mechanism 8 Next, details of the color reproduction range correction mechanism 8 will be described.
FIG. 6 is a block diagram showing a configuration example of the color reproduction range correction mechanism 8 using the correction coefficient table. In the figure, 5
Reference numeral 0 is a correction coefficient table, and 52 is an adder / subtractor. That is, the brightness and chromaticity of the input color signal (and the saturation if necessary)
From the above, the maximum reproducible saturation of the output device 12 is obtained by the color reproduction range calculation unit 6 described above, while the correction coefficient table 50 composed of a one-dimensional LUT using the chromaticity as a key is used Constant) is obtained. Then, the color reproduction range (the above-mentioned maximum saturation) and the correction coefficient are added and subtracted by the adder / subtractor 52, whereby the color reproduction range is corrected.

Here, for example, as shown in FIG. 7, the correction coefficient is incremented or incremented in accordance with the counting operation of the timer 55 for counting the elapsed time or the counter 56 for counting the number of image processes (for example, the number of copying). It is automatically updated by decrementing.
This makes it possible to easily correct the color reproduction range so as to cope with the deterioration of the output device 12 with time.

As another mode of changing the correction coefficient,
For example, the operator may set the contents of the correction coefficient table 50 via the user interface shown in FIG. The user interface shown in FIG. 8 is controlled by the control circuit shown in FIG. This circuit includes a CPU 71, a ROM 72, a RAM 73, an LCD (Liq
A uid crystal display) controller 74, a parallel interface 75, an LCD 76 and an operation panel 77.

The CPU 71 operates the LCD 76 via the LCD controller 74, and prompts the operator to operate it through the user interface shown in FIG. Further, the operation panel 77 is installed so as to overlap the LCD 76, and when the operator touches the virtual buttons 61 to 64 (see FIG. 8) displayed on the LCD 76, the CPU 71 recognizes the position,
It is designed to obtain operation information.

According to this structure, the operator selects "red", "yellow" or the like with the color selection button 61 (see FIG. 8) and inputs a desired correction amount with the numerical value input button 62, When the end button 64 is pressed, this input information is taken into the CPU 71 and the correction coefficient is set in the correction coefficient table 50. This makes it possible to easily correct an error in the color reproduction range due to a difference in machine body or the like in addition to the above-described deterioration with time.

Further, as another mode of controlling the correction coefficient, it is possible to analyze the distribution of the chromaticity of the input image at the time of prescanning and control the correction coefficient of the color reproduction range according to the analysis result. Is. FIG. 10 is a block diagram showing a configuration example of a control circuit that performs such control. As shown in the figure, this circuit includes a switch 81, a histogram creating section 82, and a correction coefficient table creating section 83.
It consists of

With such a configuration, the switch 81 switches the output of the color reproduction range calculation section 6 to the histogram creation section 82 side during the prescan, and the histogram creation section 82 creates a histogram relating to the chromaticity of the input image. . Then, after the completion of the prescan, the correction coefficient table creating unit 83
Calculates the correction coefficient of the color reproduction range based on the above histogram, and sets the result in the correction coefficient table 50.

Here, FIG. 11 shows a histogram creating section 82.
3 shows an example of a histogram created by. Since this histogram shows the appearance frequency of the input pixel with respect to the chromaticity, the correction coefficient is given as a function of this frequency as in the following expression (2). Correction coefficient = f (frequency) ……………………………………………… (2) f (): Arbitrary function

The function f () is not limited to a specific one, but if the function is set so that a correction coefficient with a higher compression rate is obtained as the frequency of appearance of pixels outside the color reproduction range increases, Even when the number of pixels outside the color reproduction range in the input image is small, it is possible to perform correction such that gradations are saved as much as possible without unnecessary compression.

The algorithm of the color reproduction range correction mechanism 8 is not limited to the above-mentioned configuration example, and can be constructed by software as a matter of course.

Saturation Compression Processing Unit 9 Next, details of the saturation compression processing unit 9 will be described. FIG.
2 is a block diagram showing a configuration example of the saturation compression processing unit 9. As shown in this figure, the saturation compression processing unit 9 is composed of a divider 122 and a multiplier 123, and linearly compresses the saturation in accordance with the ratio of the maximum saturation of the input device 1 and the output device 12. To do. That is, the divider 12
2 divides the maximum saturation of the output device 12 supplied from the color reproduction range calculation unit 6 by the maximum saturation of the input device 1 supplied from the color reproduction range calculation unit 7 and uses this result as the saturation compression coefficient. Output. Then, the multiplier 123 multiplies the saturation compression coefficient by the input saturation, and outputs the result as the compressed saturation. That is, the compressed saturation is given by the following equation (3). Compressed saturation = C _out / C _in × input saturation ………………………… (3) C _out : maximum reproducible saturation of the output device 12 C _in : reproduction of the input device 1 Maximum saturation possible

The saturation compression algorithm is not limited to the above example, and other known algorithms can of course be adopted.

Brightness Compression Processing Unit 5 Next, details of the brightness compression processing unit 5 will be described. FIG.
Reference numeral 3 is a block showing details of the brightness compression processing unit 5.
In this figure, the brightness reproduction range storage table 101 stores the maximum brightness (hereinafter referred to as a white point) and the minimum brightness (hereinafter referred to as a black point) that can be reproduced by each of the output device 12 and the input device 1. . 105 to 107 are subtractors, 108 is a divider, 109
Is a multiplier and 110 is an adder. With such a configuration, the difference between the white point and the black point is obtained for each of the output device 12 and the input device 1, and the lightness is linearly compressed based on the ratio of these differences.

That is, the compression coefficient is the output device 12
And the white point and the black point of the input device 1 are obtained from the following equation (4). Compression coefficient = (W _pout −B _pout ) / (W _pin −B _pin ) ... (4) W _pout : White point of output device 12 B _pout : Black point of output device 12 W _pin : Input White point of device 1 B _pin : Black point of input device 1

Then, the value obtained by subtracting the black point of the input device 1 from the input lightness is multiplied by the compression coefficient, and the black point of the output device 12 is added to obtain the compressed lightness by the following equation (5). Calculate by Compressed lightness = (input lightness-B _pin ) × compression coefficient + B _pout ………… (5)

The correspondence between the input lightness and the compressed lightness may be stored in the LUT, and the lightness compression result may be output by a table search using the input lightness as a key. Further, the brightness compression algorithm is not limited to the above example, and other known algorithms can of course be adopted.

(4) Summary As described above, according to the present embodiment, image processing for performing color matching processing between the image input device 1 and the image output device 12 having different color reproduction ranges by gamut compression of the color reproduction range. By providing the color reproduction range correction mechanism 8 in the apparatus, it becomes possible to perform correction corresponding to changes in the color reproduction range.

In particular, the configuration using the timer and counter shown in FIG. 7 can cope with the change in the color reproduction range due to the deterioration of the device over time. Further, with the configuration using the user interface shown in FIGS. 8 and 9, it is possible to correct an error such as a machine difference by a simple operation. Further, according to the configuration using the histogram of the input image shown in FIG. 10, it is possible to perform appropriate gamut compression processing according to the input color signal, which is more faithful to the original or more suitable for the user's purpose. It becomes possible to provide an image.

(5) Other Modifications Note that the color reproduction range of the input device 1 is corrected by the color reproduction range mechanism 8 based on the compression algorithm adopted in the saturation compression processing unit 9 and the brightness compression processing unit 5. Is also possible. Further, in the present embodiment, only the saturation and the lightness are separately compression-mapped, but even if they are compression-mapped on the plane composed of the saturation and the lightness, or in the space composed of the saturation, the lightness and the chromaticity. It may be compressed. That is, the present invention is not affected even if the algorithm of the gamut compression processing is changed. Further, the signals to be input to the saturation compression processing unit 9 and the brightness compression processing unit 5 are appropriately changed by the algorithm of the gamut compression processing to be adopted by the gamut compression processing unit 15.

B: Second Embodiment Next, a second embodiment of the present invention will be described. 14
FIG. 9 is a block diagram showing an overall configuration of an image processing apparatus according to a second embodiment of the present invention. In this figure, parts that are the same as the parts of the first embodiment shown in FIG. 1 are assigned the same reference numerals and explanations thereof are omitted. The example shown in this figure
The configuration of the gamut compression processing unit is different from that of the first embodiment shown in FIG. That is, the gamut compression processing unit 16 of this embodiment is composed of the color reproduction range conversion unit 6, the color reproduction range correction mechanism 8, the comparator 13, the saturation compression processing unit 14, and the brightness compression processing unit 5 '.

The comparator 13 compares the maximum saturation corrected by the color reproduction range correction mechanism 8 with the saturation of the input color signal to determine whether the saturation of the input color signal is outside the color reproduction range. Is determined and the determination result is output as a flag value.

As shown in FIG. 15, the saturation compression processing section 14 is composed of a selector 121, and the comparator 1
In accordance with the flag value supplied from No. 3, either the maximum saturation or the input saturation of the output device 12 supplied from the color reproduction range calculation unit 6 is selected. That is, as shown in Table 1,
When the flag value indicates outside the color reproduction range, the maximum saturation is output, and when the flag value indicates inside the color reproduction range, the input saturation is output. As a result, the input saturation is clipped by the maximum saturation that the output device 12 can output.

[0050]

[Table 1]

The brightness compression processing section 5 ', as shown in FIG. 16, has a brightness reproduction range storage table 101 and a comparator 1.
02, 103 and selector 104. The white point and the black point of the output device 12 are stored in the brightness reproduction range storage table 101, and the comparator 102 compares the white point and the input brightness. On the other hand, the comparator 103
The black point is compared with the input lightness.
Then, the selector 104 includes the comparators 102 and 103.
The brightness to be output is selected as shown in Table 2 in accordance with the result of the comparison. As a result, the input lightness is clipped by the white point and the black point of the output device 12.

[0052]

[Table 2]

According to the above-described structure, as in the first embodiment, the color reproduction range calculation section 6 corresponds to the brightness and chromaticity from the chromaticity and brightness (and saturation if necessary) of the input color signal. The color reproduction range (that is, the maximum saturation) of the output device 12 is calculated, and the result is the color reproduction range correction mechanism 8.
Is corrected in.

Then, in the comparator 13, the corrected maximum saturation is compared with the saturation of the input color signal, and the flag value indicating whether the saturation of the input color signal is outside the color reproduction range is compressed. It is supplied to the processing unit 14. In the saturation compression processing unit 14, the saturation of the input color signal is clipped according to the flag value. The brightness of the input color signal is clipped by the brightness compression processing unit 5 '.

As described above, in this embodiment, the first
Unlike the embodiment, the color reproduction range of the input color signal is compressed by a simple clipping operation. Other configurations and operations such as correction of the color reproduction range are the same as those in the first embodiment.

C: Modification of Device Configuration The present invention may be applied to a system composed of a plurality of devices or to a device composed of a single device. Further, the present invention can realize some or all of the algorithms by software.

[0057]

As described above, according to the invention described in claim 1, it is possible to easily eliminate the error due to various causes such as machine body difference without the work of changing the contents of the characteristic information. Therefore, the color reproducibility can be improved. According to the second aspect of the invention, the color reproducibility can be improved by eliminating the error caused by the deterioration over time. Further, according to the third aspect of the invention, since the correction corresponding to the characteristic of the input image data can be performed, the color reproducibility is improved by performing the color matching processing suitable for each image data. Can be planned.

[Brief description of drawings]

FIG. 1 is a block diagram showing an overall configuration of an image processing apparatus according to a first embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration example of a color reproduction range calculation unit of the image processing apparatus.

FIG. 3 is a conceptual diagram for explaining the contents of a color reproduction range storage table used in the same color reproduction range calculation unit,
(A) shows the relationship among lightness, chromaticity, and saturation, and (b) shows the contents of the table.

FIG. 4 is a conceptual diagram for explaining a method of interpolation processing performed by the same color reproduction range calculation unit.

FIG. 5 is a block diagram showing another configuration example of a color reproduction range calculation unit of the image processing apparatus.

FIG. 6 is a block diagram showing a configuration example of a color reproduction correction mechanism of the image processing apparatus.

FIG. 7 is a block diagram showing a color reproduction correction mechanism using a timer or a counter.

FIG. 8 is a plan view showing the configuration of a user interface for setting the contents of the correction coefficient table of the color reproduction correction mechanism.

FIG. 9 is a block diagram showing a configuration of a control circuit of the user interface.

FIG. 10 is a block diagram showing a color reproduction correction mechanism using a histogram.

FIG. 11 is a diagram showing an example of a histogram created by the same color reproduction correction mechanism.

FIG. 12 is a block diagram showing a configuration example of a saturation compression processing unit of the image processing apparatus.

FIG. 13 is a block diagram showing a configuration example of a brightness compression processing unit of the image processing apparatus.

FIG. 14 is a block diagram showing the overall configuration of an image processing apparatus according to a second embodiment of the present invention.

FIG. 15 is a block diagram showing a configuration example of a saturation compression processing unit of the image processing apparatus.

FIG. 16 is a block diagram showing a configuration example of a brightness compression processing unit of the image processing apparatus.

[Explanation of symbols]

 1 image input device 2, 10 color space conversion unit 3 chromaticity conversion unit 4 saturation conversion unit 5 brightness compression processing unit 6, 7 color reproduction range calculation unit 8 color reproduction range correction mechanism 9, 14 saturation compression processing unit 10 ink Plate generation / UCR processing unit 11 Image output device 13 Comparator 15, 16 Gamut compression processing unit 22 Color reproduction range storage table 50 Correction coefficient table

Front page continuation (51) Int.Cl. ⁶ Identification code Office reference number FI Technical display location G03G 15/01 115 G06T 1/00 H04N 1/46 G06F 15/66 310 H04N 1/46 Z

Claims (3)

[Claims] 1. An image processing apparatus for converting input image data so as to match characteristics of a predetermined image output apparatus, and storage means for storing characteristic information corresponding to a color reproduction range of the image output apparatus. Based on the characteristic information, a conversion unit that performs a color matching process on the image data so as to match the color reproduction range of the image output device, and a color reproduction range that is a reference of the color matching process by the conversion unit is corrected. An image processing apparatus comprising: a correction unit. 2. The image processing apparatus according to claim 1, wherein the correction amount by the correction unit is updated according to the elapsed time or the number of image outputs. 3. The image processing apparatus according to claim 1, wherein the correction amount by the correction means is determined according to the characteristics of the image data.