JPH10294879A - Color converter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a color converter where difficulty in control of total amount restriction is solved. SOLUTION: As to sets of CMY of grating point data, whether or not the total sum of the data exceeds a total amount restriction value is retrieved and when in existence, a data output value is decreased in the same ratio in the CMY. Then grating point data at which total sum of output data is contained within the total amount restriction value of an output device are calculated by the grating point data generating method and the color converter is made complete. In the form of this embodiment, without sequential execution of the processing of the total amount restriction, the total sum of data outputted from the output device is controlled to be suppressed within the maximum total amount.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a color conversion apparatus for inputting a color image signal, performing color conversion, and converting the color image signal into color image data for forming a color image.

[0002]

2. Description of the Related Art Conventional basic technology for executing only basic color conversion by interpolation calculation processing is disclosed in Japanese Patent Publication No. 58-161.
No. 80, Japanese Unexamined Patent Application Publication No. 5-75848, Japanese Unexamined Patent Application Publication No.
The invention described in JP-A-284346 can be mentioned. In the invention described in Japanese Patent Publication No. 58-16180, a unit cube is divided into tetrahedrons, which are unit interpolation sections, and it is determined which tetrahedron contains a point to be interpolated. Is linearly interpolated. According to the invention described in Japanese Patent Application Laid-Open No. 5-284346, a triangular prism is selected from the magnitude relation of input signals, and a slope coefficient and an intercept coefficient of the selected triangular prism are read from a memory. And the intercept coefficient is used to perform interpolation on the triangular prism side. Further, in the invention described in JP-A-5-284346, the three-dimensional space created by the triangularly separated input color signal is divided into rectangular parallelepipeds, and each rectangular parallelepiped is further divided into two triangular prism regions. Free color conversion and color adjustment are possible by judging whether or not it is included in the triangular prism, and performing linear interpolation using the output values at each of the six vertices of the triangular prism and rewriting the color conversion table memory. I have to.

[0003]

By the way, binary CM
When attempting to output an image from a YK color output device, the conventional method of performing basic color conversion by interpolation calculation processing is as follows:
Due to the characteristics of the output device, it is necessary to perform UCR / BG processing after color conversion and further perform total amount control processing. In addition, the raster operation is on the controller side of the output device.
In a system of an output device in which only operations on three planes of MY (or RGB) are permitted, only a simple BG / UCR for each pixel after the binarization processing and the raster operation can be executed. That is, since black is generated in pixel units, it is very difficult to regulate the total amount by the calculation formula after UCR / BG. Therefore, an object of the present invention is to provide a color conversion apparatus which solves the above-mentioned difficulty in controlling the total amount regulation.

[0004]

According to the first aspect of the present invention, a parameter storage unit for setting and storing color parameters of a point in an arbitrary color space in advance, and a parameter storage unit for performing interpolation from the parameter storage unit. In a color conversion device of a color image output device having an interpolation operation unit that reads out, the interpolation operation unit performs color conversion suitable for the color output device,
The object is achieved by controlling the data output from the color image output device not to exceed a predetermined maximum total amount value.

According to a second aspect of the present invention, in the first aspect of the invention, the color image output device is a CMYK 2
A value output device, wherein U
Even in the case where a CR / BG processing unit is provided, the data output by the color image output device after performing color conversion and UCR / BG is controlled so as not to exceed the pixel data amount corresponding to the maximum total amount. Achieve the goal.

According to a third aspect of the present invention, in the first aspect of the present invention, the interpolation operation section realizes color conversion and black generation suitable for a color image output device, and outputs the black image from the color image output output device. The above-mentioned object is achieved by controlling the data so as not to exceed the maximum total value.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of the color conversion apparatus according to the present invention will be described below in detail with reference to FIGS. First, a color conversion device used in the present embodiment will be described with reference to FIGS. FIG. 1 is a diagram showing an example of three-dimensional figure division in a three-dimensional color space, and FIG. 2 is a block diagram of a color division device. As shown in FIG. 2, the color conversion device includes a ROM (Read Only Memory) 10,
CPU (central processing unit) 12, RAM (random access memory) 14, C color processing unit 16, M color processing unit 1
8, a Y color processing unit 20. As shown in FIG. 1, when an RGB space, which is one of arbitrary input color spaces, is divided into three-dimensional figures (here, triangular prisms) and output values (here, digital CMY) at input RGB coordinates are obtained, Select the triangular prism containing the RGB coordinates
An output value is obtained by linear interpolation based on grid point data on the six vertices of the selected triangular prism. This is called a memory map method. Here, for setting the grid point data of the triangular prism, a printer simulator unique to the CMY → Lab output device that has been constructed in advance is used. The set grid point data is stored in the ROM 10 of FIG. An interpolation operation is performed in the interpolation processing unit for each color, and a final output value can be obtained.

Next, the first embodiment will be described in comparison with the prior art. FIG. 3 shows a block diagram of a conventional color image output system, and FIG. 4 shows a color image output system according to the present embodiment. FIG. 5 is a processing block diagram for generating grid point data for a conventional color conversion device, and FIG. 6 is a processing block diagram for generating grid point data for the color conversion device of the present embodiment. It is. In the processing of the conventional color image output system of FIG. 3, first, the color conversion device performs RGB-> CMY color conversion on the input image data so that the output image on the output device has a preferable color. Then, gamma correction processing is performed on the data converted to CMY, and finally, a total amount restriction process is performed so that the data does not exceed the maximum total amount value predetermined by the output device.

On the other hand, in the processing of the color image output system according to the present embodiment shown in FIG. 4, only the RGB-> CMY color conversion processing in the color conversion apparatus is performed on the input image data. That is, the function of the total amount regulation process is RG
B-> CMY color conversion. this is,
In other words, the control of the total amount of output image data is controlled by the grid point data used for the interpolation of the RGB-> CMY color conversion.

Next, a method of generating grid point data for the color conversion apparatus according to the present embodiment will be described with reference to FIG. First,
RGB coordinate data of a grid point of the color conversion device is prepared as input data. Also, when the coordinate values are input to the color conversion device at the same time, it is desired that the output value be output from the output device.
Determine the value of Lab for get. Then, triangular prism interpolation is performed on RGB (at this point, the grid point data contains an appropriate CMY value as an initial value), and the obtained CMY
The CMY-> Lab conversion is performed by a printer simulator unique to the output device created in advance.
Then, the Lab value is compared with the Lab of the Target to obtain the color difference ΔELab, and the process of optimizing the grid point data of the triangular prism interpolation is repeated so that the color difference is minimized. The data thus obtained is the basic color conversion grid point data of RGB → CMY.

Regarding the CMY set of the grid point data,
A search is made to see if the sum of the data exceeds the total amount regulation value. If there is, the output value of the data is reduced at the same rate as CMY. This processing corresponds to the total amount restriction processing. This is different from the case where the total amount is regulated after the gamma conversion shown in FIG. By the above grid point data creation method, grid point data in which the sum of all output data falls within the total amount regulation value of the output device is calculated, and the color conversion device is completed. As described above, in this embodiment, it is possible to control the total amount of data output from the output device to be within the maximum total amount value without sequentially executing the total amount control process.

Next, a second embodiment of the present invention will be described in comparison with a conventional technique. FIG. 7 is a block diagram of a conventional color image output system, and FIG. 8 shows a color image output system according to the present embodiment. FIG. 9 is a processing block diagram for creating grid point data for the color conversion apparatus according to the present embodiment. In the processing of the conventional color image output system shown in FIG. 7, the color conversion device uses RGB-> CM such that the output image on the output device has a preferable color.
The Y color conversion is performed on the input image data. And C
A gamma correction process is performed on the data converted to MY, and then a binarization process is performed.

Subsequently, UCR / BG in pixel units is executed for the CMY three color outputs after the binarization processing, and CMYK4
This is a process of obtaining color output data. here,
Since UCR / BG is not black generation based on CMY data values but black generation in pixel units, it is impossible to control the total amount regulation value (determined by the data value) determined by the output device. On the other hand, in the processing of the color image output system according to the present embodiment shown in FIG. 8, UCR / BG in pixel units after RGB-> CMY color conversion processing and binarization processing on input image data in the color conversion apparatus Processing is performed. The control corresponding to the total amount regulation is performed by the RGB-> CMY color conversion processing as in the first embodiment.

Referring to FIG. 9, a method of creating grid point data for the color conversion apparatus according to the present embodiment will be described. Before executing the creation method of FIG. 9, beforehand (after binarization, U
A table of “total number of pixels after execution of CR / BG” vs (total number of pixels after binarization of normal data values not subjected to UCR / BG processing) is created. By creating this table, it is possible to calculate which level value the image after UCR / BG execution of the pixel unit after binarization is converted into the data amount before binarization. Subsequently, in the same manner as in the first embodiment, grid point RGB coordinate data of a grid point for a color conversion device and a Lab value of Target are prepared, and triangular prism interpolation and CMYK → Lab conversion by a printer simulator are performed. Perform optimization processing to minimize ΔELab. Here, the CMYK-> Lab printer simulator differs from the first embodiment, and the simulator includes UCR / BG processing in pixel units. Further, the CMY grid point data obtained by the optimization processing of FIG.
The output value after the pixel unit UCR / BG after the binarization is calculated to which level before the binarization, and if the level exceeds the level corresponding to the total amount regulation value, the data is output at the same rate as CMY. Decrease the value. With the above grid point data creation method, grid point data in which the sum of all output data falls within a level equivalent to the total amount regulation value of the output device is calculated, and a color conversion device having a function equivalent to the total amount regulation is completed. In this embodiment, control is performed so that the data output after performing the color conversion and the UCR / BG does not exceed the pixel data amount corresponding to the maximum total amount value.

Next, a third embodiment will be described. FIG. 10 is a block diagram of a conventional color image output system, and FIG. 11 is a diagram of a color image output system according to the third embodiment. Also, in FIG.
A processing block diagram for creating grid point data for the color conversion device of the present embodiment is shown. In the same manner as in the first embodiment, grid point data incorporating a UCR / BG function and a total amount control function is calculated. However, the printer simulator performs the conversion of CMYK → Lab. And the first
The total amount restriction processing is performed on the CMYK grid point data calculated in the same manner as in the embodiment and the second embodiment.
In this embodiment, for input color image data,
Since it is possible to control the generation of the data black output from the output device and the control of the total value within the maximum total value without successively executing the UCR / BG and the total amount control processing, the color image output system as a whole The required processing time until output can be greatly reduced.

[0016]

According to the first aspect of the present invention, it is possible to control the total amount of data output from the output device to be within the maximum total amount without sequentially executing the total amount control process. Thus, the required processing time until output can be greatly reduced. According to the second aspect of the present invention, only processing in 3 planes is allowed before the raster operation, and even when only UCR / BG in pixel units can be performed for black generation, the data output from the output device is maximum. It is possible to perform control to keep the pixel data amount within the total amount value. According to the third aspect of the present invention, UCR is performed on input color image data in the color image output system.
/ BG and total amount regulation processing without executing
Since it is possible to control the generation of the data black output from the output device and to suppress the total value within the maximum total value, the processing time required until the output can be greatly reduced when the entire color image output system is viewed.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an arbitrary input color space used in a color conversion apparatus according to an embodiment.

FIG. 2 is a block diagram of a color conversion device used in the present embodiment.

FIG. 3 is a block diagram of a conventional color image output system for explaining the first embodiment.

FIG. 4 is a diagram illustrating a color image output system according to the first embodiment.

FIG. 5 is a processing block diagram for creating grid point data for a conventional color conversion device for explaining the first embodiment.

FIG. 6 is a processing block diagram for creating grid point data for the color conversion device according to the first embodiment.

FIG. 7 is a block diagram of a conventional color image output system for explaining a second embodiment.

FIG. 8 is a block diagram of a color image output system according to a second embodiment.

FIG. 9 is a processing block diagram for creating grid point data for a color conversion device according to a second embodiment.

FIG. 10 is a block diagram of a conventional color image output system for explaining a third embodiment.

FIG. 11 is a block diagram of a color image output system according to a third embodiment.

FIG. 12 is a processing block diagram for creating grid point data for a color conversion device according to a third embodiment.

[Explanation of symbols]

 Reference Signs List 10 ROM 12 CPU 14 RAM 16 C color processing unit 18 M color processing unit 20 Y color processing unit

Claims (3)

[Claims] 1. A color image output apparatus comprising: a parameter storage unit for previously setting and storing a color parameter of a point in an arbitrary color space; and an interpolation operation unit for reading parameters from the parameter storage unit at the time of interpolation. In the color conversion device, the interpolation operation unit performs color conversion suitable for a color output device, and controls so that data output from the color image output device does not exceed a predetermined maximum total amount value. Color conversion device. 2. The color image output device is a CMYK 2
A value output device, wherein U
Even when a CR / BG processing unit is installed, control is performed so that data output from the color image output device after performing color conversion and UCR / BG does not exceed the pixel data amount corresponding to the maximum total amount value. The color conversion device according to claim 1. 3. The interpolation operation unit realizes color conversion and black generation suitable for a color image output device, and controls data output from the color image output device so as not to exceed a maximum total amount value. The color conversion device according to claim 1, wherein: