JPH08294010A - Image processing unit, its method and system - Google Patents

Abstract

PURPOSE: To provide the image processing unit and its method by which a color of an output image by the image processing unit is equal to the color obtained by offset printing by taking under-color reduction (UCR) in the offset printing into account. CONSTITUTION: A K component of a received CMYK signal is converted into shares ΔC, ΔM, ΔY to other CMY component by taking the UCR in the offset printing into account by allowing a 1st conversion section 20 to reference an LUT section 50. Then, each color component of the CMY signal is added by an arithmetic circuit 30, the sum is converted into an RGB signal by a 2nd conversion section 40 and displayed by a display section 200.

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 and method and system, and more particularly to an image processing apparatus and method and system for visualizing a full color image.

[0002]

2. Description of the Related Art In recent years, a color plate making system including a personal computer, a full-color scanner, a film scanner, a full-color high-definition display, a full-color printer, application software, etc. has become widespread due to its low price and high functionality. There is. As a result, among the work processes in full-color offset printing, which were not easily performed in the past, until the color comp, which is a printing sample, is created by the operator of the color plate making system at a relatively low cost and in a short period of time. It is becoming possible to do it.

Generally, in offset printing, a color is mixed by changing the halftone dot area ratio of each offset ink of C (cyan), M (magenta), Y (yellow), and K (black), and printing is performed. Often output. Therefore, in order to create a color comp for offset printing by the color plate making system, it corresponds to the halftone dot area ratio of C, M, Y, and K inks in offset printing (hereinafter referred to as CMYK halftone dot area ratio). Live CM
It is necessary that the tint of the output image obtained when the input image represented by the YK image signal is input to the color plate making system for processing and output is almost the same as the tint in the printing result of the offset printing. Become.

Regarding the conventional method for making the tint of the color plate making system almost equal to the tint of the offset printing,
This will be described below.

As an example of a structure for outputting an image in a color plate making system, a color display is taken as an example.
In the input image represented by the CMYK image signal corresponding to the CMYK halftone dot area ratio, R (red), G (green) is obtained by taking the complement of the signal value level "255" for each C, M, Y signal. ), B (blue) signal. Then, the output image is displayed on the screen of the color display based on the obtained RGB signal values.

As an example of a structure for performing image output in a color plate making system, a full-color printer is taken as an example, and in the input image represented by CMYK image signals corresponding to the CMYK halftone dot area ratio, the respective C, M, Y, and K
Correction is performed by multiplying the signal by a predetermined coefficient. By this correction, the difference between the tint of the output image output by the full-color printer and the tint of the print result of offset printing is corrected, and thus full-color output with the tint equivalent to that of offset printing is possible.

[0007]

However, the above-mentioned conventional example has the following problems.

For example, in the case where the structure for outputting an image in a color plate making system is a color display, a CM
Although it is converted into an RGB signal by taking the complement of the CMY components of the input image represented by the YK signal, this method does not process the K signal in the input image. Therefore, the K component is not taken into consideration in the tint displayed on the color display, and it is not always the same as the tint in the offset printing result. In addition, CMYK
It is possible to perform conversion into an RGB signal in consideration of the K component of the signal, for example, by considering stochastic overlap of respective color inks and dot arrangement according to Neugebauer's equation, but this method requires complicated calculation. However, the processing becomes complicated, resulting in an increase in processing time and an increase in cost.

On the other hand, when the configuration for outputting an image in the color plate making system is a full color printer, CMY
For each CMYK component of the input image represented by the K signal,
It is corrected by multiplying it by a predetermined coefficient. In this method, K
Since the components are taken into consideration, the above problem does not occur. However, since only CMYK signals are handled, it is not possible to deal with the case of outputting in other signal formats such as RGB signals.

In any of the above methods,
The input image signal represented by the CMYK signal is uniformly complemented or multiplied by a coefficient. That is, the difference in color reproducibility due to the configuration for outputting an image, for example, the difference in color reproducibility due to the device color reproduction method is not taken into consideration. Therefore, for example, even when a correction is applied to a certain tint, it is necessary to uniformly take a complement or multiply it by a predetermined coefficient, which will affect all other tints.

Due to the various problems described above,
In the conventional color plate making system, it was difficult to make the tint of the output image equal to that of the offset printing.

The present invention has been made to solve the above-mentioned problems, and by taking into consideration undercolor removal (UCR) in offset printing, the tint of an output image obtained by an image processing apparatus can be obtained by offset printing. It is an object of the present invention to provide an image processing apparatus, a method thereof, and a system having the same color tone.

[0013]

In order to achieve the above object, the image processing apparatus of the present invention has the following configuration.

That is, the input means for inputting the color image signal of the first format and the black component of the color image signal of the first format are converted into color components other than black in the first format based on a predetermined relationship. Addition for adding a color component other than black in the first format converted by the first conversion means to a color component other than black in the color image signal of the first format input by the input means Means, second conversion means for converting color components other than black of the color image signal of the first format added by the adding means into a color image signal of a second format different from the first format, and the second conversion Output means for outputting the color image signal of the second format converted by the means.

For example, the first format is a CMYK density expression, and the second format is a RGB brightness expression.

For example, the first format is a density expression in CMYK corresponding to a halftone dot area ratio in offset printing.

For example, the output means displays and outputs the color image signal of the second format.

For example, the output means prints out the color image signal of the second format.

For example, the first conversion means is characterized in that the K component is converted into a CMY component on the basis of the halftone dot area ratio relationship for each color component of the CMYK signals in offset printing.

For example, the first conversion means is characterized by performing conversion by referring to a table.

For example, the first conversion means is characterized by performing conversion by multiplying the K component by a predetermined coefficient.

In order to achieve the above object, the image processing method of the present invention comprises the following steps.

That is, an input step of inputting a color image signal of the first format and converting a black component of the color image signal of the first format into a color component other than black in the first format based on a predetermined relationship. Addition for adding a first conversion step and a color component other than black in the first format converted by the first conversion step to a color component other than black of the color image signal of the first format input by the input means. A second conversion step of converting a color component other than black of the color image signal of the first format added by the addition step into a color image signal of a second format different from the first format, and the second conversion And an output step of outputting a color image signal of the second format converted by the step.

In order to achieve the above object, the image processing system of the present invention comprises the following means.

That is, the input means for inputting the color image signal of the first format and the black component of the color image signal of the first format are converted into color components other than black in the first format based on a predetermined relationship. Addition for adding a color component other than black in the first format converted by the first conversion means to a color component other than black in the color image signal of the first format input by the input means Means, second conversion means for converting color components other than black of the color image signal of the first format added by the adding means into a color image signal of a second format different from the first format, and the second conversion Output means for outputting the color image signal of the second format converted by the means.

[0026]

With the above construction, it is possible to convert the color image signal of the first format into the color image signal of the second format by removing the black component in consideration of the black component amount.

Therefore, the RG capable of processing the CMYK signals corresponding to the dot area ratio in the offset printing by the output means.
Since the conversion to the B signal can be appropriately performed, the unique effect that the tint of the image output from the image processing apparatus can be made substantially the same as the tint obtained by the offset printing is obtained.

[0028]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment according to the present invention will be described in detail below with reference to the drawings.

<First Embodiment> FIG. 1 is a block diagram showing the arrangement of an image processing apparatus according to this embodiment. In FIG. 1, an image processing unit 100 is connected to a display unit 200 such as a color monitor and a print output unit 300 such as a color printer.
Reference numeral 400 denotes a host computer, which is an image processing unit 100.
And is connected via an interface. Also, 50
An image input unit 0 such as a scanner reads a document image and inputs it to the image processing apparatus. An operation unit 600 such as a keyboard is used to input instructions and data from an operator to the system.

FIG. 2 shows a detailed configuration of the image processing unit 100. In FIG. 2, 10 is, for example, the host computer 4
00 is an image memory that stores image signals expressed by CMYK. Of course, the image signal stored in the image memory 10 may be one created by the image processing apparatus itself, or one read by the image input unit 500 such as a scanner,
It may be read from an external storage device or the like (not shown) connected to the image processing unit 100.

Reference numeral 20 denotes a first conversion unit, which refers to the LUT unit 50 and distributes the K component of the CMYK image signals stored in the image memory 10 to the other three color components C, M, and Y. The amounts ΔC, ΔM, and ΔY to be determined are determined by direct mapping with reference to the LUT unit 50, and C, M, Y, and ΔC,
Outputs ΔM and ΔY. Details of the first conversion unit 20 will be described later. Reference numeral 30 denotes an arithmetic circuit, which receives the input C,
ΔC, ΔM, and ΔY are added to the M and Y components, respectively.
40 is a second conversion unit, which refers to the LUT unit 50 and
A format in which the image signal expressed by MY can be output on the display unit 200, that is, R which can be displayed on a color monitor or the like.
Convert to GB format.

The LUT unit 50 is composed of a RAM,
A plurality of LUTs are provided, and each of these LUTs will be described later.

Reference numeral 60 denotes a CPU, which comprehensively controls the respective components of the image processing unit 100 described above. Reference numeral 61 denotes a ROM, which holds a control program executed by the CPU 60, fixed variables, and the like. Reference numeral 62 is a RAM that serves as a work area for the CPU 60.

The RGB signals output from the image processing device are input to the display section 200 and visualized on the screen.

Hereinafter, the image processing unit 10 having the above-mentioned configuration
The operation at 0 will be described in more detail with reference to the flowchart of FIG.

First, in step S 401, an image signal expressed in CMYK is input from the host computer 400, for example, and is stored in the image memory 10. Then, the process proceeds to step S402, and the CM stored in the image memory 10
The YK image signal is input to the first conversion unit 20. The first conversion unit 20 converts the K component in the input image signal into C, M, Y
In order to determine the amounts ΔC, ΔM, ΔY to be distributed to the components,
Although the LUT prepared in advance in the LUT unit 50 is referred to,
Among the plurality of LUTs stored in the LUT unit 50, an appropriate LUT is selected according to the input CMYK signal.

Here, referring to FIG. 4, the LUT described above is used.
The LUT stored in the unit 50 will be described.

FIG. 4 shows the K component density (gray density) in the original printed by the offset printing and the separated halftone dot area ratios of the C, M and Y components corresponding to the K component in the offset printing (hereinafter referred to as halftone dots). It is a figure which shows the relationship of (%). The horizontal axis of FIG. 4 represents the halftone dot% of the K component, the vertical axis represents C,
The halftone dots% of the M and Y components are shown. That is, in an offset-printed document, for example, when the halftone dot% of the K component of the document is about 35%, and when the K component is replaced with C, M, and Y component inks, the C component is about 15%. It is shown that it is sufficient to increase the halftone dot percentage of about 28% for the M, Y components.
In FIG. 4, the curves showing the dot% of the C component and the M and Y components are different. In general, the ink used in offset printing does not have an ideal subtractive color mixture because it contains unnecessary absorption components as compared with an ideal spectral curve. Therefore, in this embodiment, this is corrected by increasing the halftone dot% of the Y and M components when replacing the K component as compared with the C component. In FIG. 4, M,
The curves showing the dot% of the Y component are the same, but this is an example of correcting unnecessary components. That is, the curve indicating the halftone dot% of the M and Y components may differ depending on the characteristics of the ink used in offset printing.

In this embodiment, ΔC, ΔM, and ΔY are estimated as the amounts of C, M, and Y components corresponding to the K component based on the relationship shown in FIG. Then, the relationship is created in advance in the LUT unit 50 as an LUT. Here, ΔC, ΔM, and ΔY are amounts by which the K component is replaced by the C, M, and Y components, and for example, K = 5% halftone dot%.
If ΔC = 4%, ΔM = 4%, ΔY = 4%, that is, the hue printed with K = 5% in the offset printing and C = 4%, M = 4%, Y = 4% The shades printed with the three colors are the same.

The relationship of the dot% in each color component shown in FIG. 4 described above is an example in offset printing, and the present invention is not limited to this. Therefore, the curve of each color component can be arbitrarily corrected. Therefore, Δ corresponding to the K component
By changing C, ΔM, and ΔY, the LUT unit 50
Of course, it is possible to newly create the LUT data in the above. Therefore, the LUT unit 50 can create and store an appropriate LUT according to the characteristics of the image signal to be processed, and a plurality of LUTs can be prepared and placed.

In FIG. 3, the process proceeds to step S403, and the first conversion unit 20 refers to the LUT in the LUT unit 50 created as described above,
An appropriate Δ based on the K component of the input CMYK signal
Obtain C, ΔM, ΔY. Then, the first conversion unit 20 outputs the C, M, and Y components of the input CMYK signal as they are, and further outputs ΔC, ΔM, and
Output ΔY.

Next, in step S404, C, M, Y, ΔC, ΔM, output from the first conversion LUT 20.
Each signal of ΔY is input to the arithmetic circuit 30, and each C, M, Y
ΔC, ΔM, and ΔY are added to the components to obtain C ′, M ′, and Y ′.
Is output as That is, C ′ = C + ΔC, M ′ = M +
ΔM, Y ′ = Y + ΔY.

Then, in step S405, the second converter 40 converts the input C ', M', Y'signals into R, G, B signals that can be output by the display 200. The conversion in the second conversion unit 50 is performed by a matrix operation, direct mapping, or C,
This is realized by taking the complement of "255" of the M and Y signals. Then, the converted RGB signal is output to the display unit 200 in step S406 and displayed in the same tint as the output by the offset printing.

The color conversion process of this embodiment is performed as described above. Next, the process of changing and newly creating the LUT in the LUT unit 50 will be described with reference to the flowchart of FIG. .

First, in step S501, the operation unit 6
00, it is determined whether or not an instruction to update the LUT has been issued. If the update instruction has not been issued, the update processing is not performed, but if the update instruction has been issued, the process proceeds to step S502, and the update target is selected from the plurality of LUTs existing in the LUT unit 50. Select the LUT. Here, for example, all the LUTs in the LUT unit 50 may be displayed on the display unit 200 and the operator may select them on the screen. Further, when creating a new LUT, an instruction to that effect is issued from the operation unit 600. Then, the selected LUT is read out to the RAM 62.

Then, in step S503, the LUT selected in step S502 is updated. That is, the LUT value obtained by changing the relationship for each color component shown in FIG. 4 described above is updated by the operation unit 600. Then, in step S504, the LUT updated in the RAM 62 is stored in the LUT unit 50.

As described above, the LUT in this embodiment
Is updated or newly created. Then, the updated or newly created LUT is referred to by the first conversion unit 20 according to the processing shown in FIG.

As described above, according to the present embodiment, the CMYK signal can be converted into the RGB signal in consideration of the undercolor removal (UCR) process in the offset printing, and thus the hue to be output in the offset printing. And the hue displayed on the display unit 200 can be made substantially the same.

<Second Embodiment> The second embodiment according to the present invention will be described below. The configuration of the color image processing system in the second embodiment is the same as that of the first embodiment shown in FIG.
The detailed configuration of the image processing unit 100 is shown in FIG.

In the first embodiment described above, the CMYK signals input to the image processing unit 100 are distributed to the C, M, Y, ΔC, ΔM and ΔY signals in the first conversion unit 20 and added in the arithmetic circuit 30. By doing so, it was converted into C ′, M ′, Y ′ signals. In the first embodiment, the values of ΔC, ΔM, and ΔY corresponding to the K component are directly obtained by direct mapping in the first conversion unit 20. In the second embodiment, a first conversion unit 70 is used instead of the first conversion unit 20 shown in FIG.
In the first converter 70, each C,
It is characterized in that ΔC, ΔM, and ΔY are determined by multiplying the M and Y components by a coefficient according to the magnitude of the K component. That is, the data content of the LUT to be referred to is different from that in the first embodiment.

Referring to FIG. 7, the first embodiment of the second embodiment
The processing of the conversion unit 70 will be described. FIG. 7 is a diagram conceptually showing the processing in the first conversion unit 70, and shows an example of the LUT referred to in the first conversion unit 70. In addition, in FIG. 7, the numerical value in () shows each component value.

In the first conversion section 70, ΔC and Δ corresponding to the K component are directly mapped to the LUT.
Instead of directly obtaining the values of M and ΔY, a predetermined coefficient is obtained for each of ΔC, ΔM, and ΔY according to the value of the K component. For example, the color components of the input CMYK signals are sequentially (3
0, 60, 40, 5), the first conversion unit 70 refers to the LUT in the LUT unit 50 to obtain ΔC, ΔM, when the K component is “5”. Δ
The coefficient of Y "0.8" is obtained. Then, by multiplying the K component by the obtained coefficient, respectively,
Determine C, ΔM, ΔY. Therefore, ΔC =
After the calculation of 0.8 × 5, ΔM = 0.8 × 5, ΔY = 0.8 × 5 is performed, (C, M, Y, ΔC, ΔM, Δ
Y) = (30,60,40,4,4,4) is output.

Then, in the arithmetic circuit 30 of the next stage, C,
ΔC, ΔM, and ΔY are added to the M and Y components, respectively, so that C ′ = 34, M ′ = 64, and Y ′ = 44 are output. Then, after that, as in the above-described first embodiment, the signals are converted into RGB signals by the second conversion unit 40 and displayed on the display unit 200.

As described above, according to the second embodiment as well, similar to the above-described first embodiment, color conversion can be performed in consideration of the K component of the input image signal. It is possible to make the shades displayed on the screen almost the same.

In the first and second embodiments described above, an example in which the RGB signals converted by the image processing unit 100 are displayed on the display unit 200 has been described, but of course the RGB signals are output to the printing unit 300. May be. In the printing unit 300, the RGB output from the image processing unit 100
By receiving the signal and printing it on the recording medium, it is possible to form an image having a tint equivalent to that of offset printing. Since the printed matter output from the printing unit 300 can be sufficiently utilized as a master plate in offset printing due to its color reproducibility, the system configuration to which the image processing apparatus of the present invention is applied is a color plate making system for offset printing. Is also applicable.

The present invention may be applied to a system composed of a plurality of devices or an apparatus composed of a single device. Further, it goes without saying that the present invention can be applied to the case where it is achieved by supplying a program to a system or an apparatus.

[0057]

As described above, according to the present invention, C
By inputting a CMYK image signal corresponding to the MYK halftone dot area ratio and distributing the K component to each CMY component so as to have a predetermined halftone dot area ratio relationship, undercolor removal in offset printing for the input signal ( Since UCR) can be taken into consideration, an image can be output with a color tone that is almost the same as the color tone that is output by offset printing in the image output unit.

Also, the update of the halftone dot area ratio relationship for distributing the K signal can be easily performed by updating the LUT data.

[0059]

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of a color image processing system that is an embodiment of the present invention.

FIG. 2 is a block diagram showing a detailed configuration of an image processing unit 100 in this embodiment.

FIG. 3 is a flowchart showing a color conversion process in this embodiment.

FIG. 4 is a diagram showing a relationship of a separated halftone dot percentage in each color component of CMYK of offset printing in the present embodiment.

FIG. 5 is a flowchart showing LUT update processing in this embodiment.

FIG. 6 is an image processing unit 1 according to a second embodiment of the present invention.
It is a block diagram which shows the detailed structure of 00.

FIG. 7 is a diagram for explaining the operation of the first conversion unit in the second embodiment.

[Explanation of symbols]

 10 image memory 20 1st conversion part 30 arithmetic processing part 40 2nd conversion part 50 LUT part 60 CPU 61 ROM 62 RAM 100 image processing part 200 display part 300 printing part 400 host computer 500 image input part 600 operation part

Claims (17)

[Claims] 1. Input means for inputting a color image signal of a first format, and converting a black component of the color image signal of the first format into a color component other than black in the first format based on a predetermined relationship. Addition for adding a color component other than black in the first format converted by the first conversion means to a color component other than black in the color image signal of the first format input by the input means Means for converting color components other than black of the color image signal of the first format added by the adding means into a color image signal of a second format different from the first format; and the second conversion means. And an output unit that outputs the second-format color image signal converted by the unit. 2. The image processing apparatus according to claim 1, wherein the first format is a density expression in CMYK and the second format is a brightness expression in RGB. 3. The image processing apparatus according to claim 2, wherein the first format is a CMYK density expression corresponding to a halftone dot area ratio in offset printing. 4. The image processing apparatus according to claim 1, wherein the output unit displays and outputs the color image signal of the second format. 5. The image processing apparatus according to claim 1, wherein the output unit prints out the color image signal of the second format. 6. The image according to claim 3, wherein the first conversion unit converts the K component into the CMY component based on the relationship of the halftone dot area ratio for each color component of the CMYK signals in the offset printing. Processing equipment. 7. The image processing apparatus according to claim 6, wherein the first conversion unit performs conversion by referring to a table. 8. The image processing apparatus according to claim 6, wherein the first conversion unit performs conversion by multiplying the K component by a predetermined coefficient. 9. An input step of inputting a color image signal of a first format, and converting a black component of the color image signal of the first format into a color component other than black in the first format based on a predetermined relationship. A first conversion step, and an addition for adding the color component other than black in the first format converted by the first conversion step to the color component other than black of the color image signal of the first format input by the input unit. A second conversion step of converting color components other than black of the color image signal of the first format added by the adding step into a color image signal of a second format different from the first format; An output step of outputting a color image signal of the second format converted by the step; and an image processing method. 10. The image processing method according to claim 9, wherein the first format is a density expression in CMYK and the second format is a brightness expression in RGB. 11. The image processing method according to claim 10, wherein the first format is a CMYK density expression corresponding to a halftone dot area ratio in offset printing. 12. The image processing method according to claim 9, wherein in the output step, the color image signal of the second format is output for display. 13. The image processing method according to claim 9, wherein in the outputting step, the color image signal of the second format is printed out. 14. The K component is converted into a CMY component in the first converting step based on a relationship of a halftone dot area ratio for each color component of a CMYK signal in offset printing. Image processing method. 15. The image processing method according to claim 14, wherein in the first converting step, conversion is performed by referring to a table. 16. The image processing method according to claim 14, wherein in the first converting step, conversion is performed by multiplying the K component by a predetermined coefficient. 17. Input means for inputting a color image signal of a first format, and converting a black component of the color image signal of the first format into a color component other than black in the first format based on a predetermined relationship. Addition for adding a color component other than black in the first format converted by the first conversion means to a color component other than black in the color image signal of the first format input by the input means Means for converting color components other than black of the color image signal of the first format added by the adding means into a color image signal of a second format different from the first format; and the second conversion means. An image processing system comprising: an output unit that outputs a color image signal of a second format converted by the unit.