JP2894429B2 - Color correction method for color printer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color correction method for a color printer, and more particularly to a color correction method for a color printer by a gradation processing method using a dither method.

[0002]

2. Description of the Related Art Japanese Patent Laid-Open No. 4-345366 is known as an example of a conventional gradation processing method using a dither method.
This gradation processing method divides pixel data into a high-density area and a low-density area in order to eliminate density unevenness and secure a predetermined resolution, and forms a dither matrix on the pixel data in the low-density area. The output of the converted value by the threshold level is R
This is performed using an OM (read only memory).

That is, image data expressed by multi-level gradation levels is divided into pixel data of a high-density area and pixel data of a low-density area for each pixel using a predetermined density level as a threshold value. The pixel data of the area is output as it is,
The pixel data of the low-density area is output after being subjected to area gradation processing. Further, the area gradation processing is a dither processing for outputting a value obtained by converting pixel data of an m × n matrix according to a corresponding threshold level of an m × n dither matrix.

[0004]

However, in this conventional gradation processing method, the threshold level of the dither matrix is determined from the image characteristics of the printer to be used, and the ROM is used.
Since this is stored and used, if the subtle changes in gradation, density, etc. are to be made by changing the threshold level of the dither matrix, the ROM must be replaced. There's a problem.

[0005]

According to the present invention, the contents of an image memory are output to a printing unit by a gradation processing method using a dither method.
In the color correction method of a color printer to print, and Li
The near input threshold is determined by a predetermined correction formula.
Ri corrected has a correcting section that outputs the integer, the input threshold, the given through correcting unit in the memory of the dither matrix for each color, output threshold which is the output of the memory
The value and the input image data are compared by the comparing unit to be binarized.
The comparison result is stored in the image memory, and a rewritable memory is used as the memory.

[0006]

According to the present invention, the image memory and the image memory
Connects a calculation unit to change the density with the printing unit
The arithmetic unit outputs the output of the dither matrix and a user
Generated based on the concentration command specified by the user
To increase or decrease the concentration of the specified concentration range.
Output of the image memory based on a specified control command
Color pre-adjustment by adjusting the density
Thus, a color correction method for the printer can be obtained.

[0008]

The threshold value to be stored can be promptly converted to a desired value by making the dither matrix rewritable.

[0009] Further, the gradation can be improved by arranging the threshold dither matrix in a supercell arrangement by combining basic matrices.

[0010] In addition, by controlling the output of the image memory by the output of the changed dither matrix, it is possible to print a corrected image using the image memory as it is, and it is not necessary to reproduce the image memory.

[0011]

Next, the present invention will be described with reference to the drawings. FIG. 1 is a configuration diagram of a first embodiment of the present invention. The dither matrix 1 is stored in a rewritable memory, where 1-1 is a yellow (Y) matrix, 1-2 is a magenta (M) matrix, 1-3 is a cyan (C) matrix, and 1- 1 4 is a black (K) matrix. This dither matrix 1 has an input threshold (multi-value)
2 is provided through the correction unit 3. Dither matrix 1
Output threshold value (multi-valued) 4 is given to the comparison unit 6. The comparison unit 6 compares the input image data 5 with the output threshold value 4 and outputs a comparison result output (binary) 7 to the image memory 8.
The image memory 8 includes a yellow (Y) image memory 8-1, a magenta (M) image memory 8-2, a cyan (C) image memory 8-3, and a black (K) image memory 8-4. The data read from the image memory 8 is transmitted to the printing unit 9.
Is output to

In FIG. 1, a dither matrix 1-1 (Y)
Numerals 1 to 16 indicate the order of the threshold values and 16 gradations. When there is no correction as the threshold value, a linear number, for example, 00 ^H 10 ^H 20 ^H ... D0 ^H E0
^H F0 ^H is stored (here, H indicates hexadecimal). Dither matrix 1-2 (M), 1-3
(C) and 1-4 (K) are similarly stored.

If there is a correction, a linear input threshold 2
Are stored in the dither matrix 1 after being corrected by the correction unit 3. For example, Z = Z ′ ^γ (Z: output, Z ′: input, where 0 ≦
When integer by multiplying the linear value as gamma = 1.4 by the correction equation Z '≦ 1), the ^{00 H 05 H 0E H ... C0} H D5 H EA H.

The rows and columns of the dither matrix 1 are addressed corresponding to the pixels of the input image data 5, the threshold value of the address is read out as the output threshold value 4, and the size of the input image data 5 is compared. The data is binarized by comparison by the unit 6 and stored in the image memory 8. That is, if the input image data 5 is yellow (Y), the yellow (Y) matrix 1-1 is accessed, and the comparison result is stored in the yellow (Y) image memory 8-1. If the input image data 5 is magenta (M), the magenta (M) matrix 1-2 is accessed and stored in the magenta (M) image memory 8-2, where cyan (C) and black (K) are stored. Is similarly processed.

When data for one page printing is stored in the image memory 8 in this manner, the contents of the image memory 8 are stored in the order of yellow (Y), magenta (M), cyan (C), and black (K). It is sent to the printing unit 9 and printed on a printing paper or the like.

FIG. 2 is a block diagram of a second embodiment of the present invention, which is based on the dither matrix shown in FIG.
Are combined into one matrix. That is, 1-1-A (Y) represents the first basic matrix of yellow (Y), and 1-1-B (Y) represents the second, 1-1- (Y).
C (Y) indicates a third basic matrix, and 1-1-D (Y) indicates a fourth basic matrix. As a result, there are a total of 64 threshold values, and there are 64 gradations (per color). The same applies to the matrices of magenta (M), cyan (C), and black (K).

From the input threshold 2, 64 types of thresholds are input and stored in the dither matrix 1.
Dither matrix 1 corresponding to the pixels of input image data 5
Are addressed, and the threshold value of the address is read out. The magnitude of the read output threshold value 4 and the input image data 5 are compared by the comparing unit 5, and the binarized comparison result output 7 is stored in the image memory 8 and further sent to the printing unit 9. Printed. Note that, in FIG. 2, the correction unit 3 illustrated in FIG. 1 is not illustrated for convenience.

FIG. 3 is a block diagram of a third embodiment of the present invention. In this embodiment, the output threshold value 4 of the dither matrix 1 is also input to the calculation unit 10. The image memory 8 is read out in units of the number of elements (number of gradations / colors) of one matrix of the dither matrix 1 and input to the arithmetic unit 10. The operation unit 10 performs an operation based on the output threshold value 4 of the dither matrix 1, the output of the image memory 8, and the control command 11, and the result is output to the printing unit 9 and printed. Note that the control command 11 is sent from a control unit or a host computer (neither is shown) that has received a command regarding the density designated by the user. Also, in FIG. 3, it is assumed that the contents of the image memory 8 are repeatedly printed many times, and the correction unit 3 and the comparison unit 6 shown in FIG. 1 are omitted for convenience.

FIGS. 4 and 5 are block diagrams for explaining the operation of the arithmetic unit 10. FIG. 4A shows a dither matrix input to the arithmetic unit 10, and FIG.
Is the contents of the image memory input to the. I in FIG. 4 (b)
1 and I2 indicate a pixel ON, and I3 indicates a pixel to be turned ON next when the density is to be increased. Control command 11
If the content is to increase the density of the low density area by one pixel, the arithmetic unit 10 reads patterns sent one after another from the image memory 8 and, if the pattern shown in FIG. Next, the pixel I3 to be turned on is turned on. In this way, without the time-consuming reproduction of the image memory, that is, while keeping the image memory,
The density in the low density range can be increased.

FIG. 5A shows the contents of the image memory input to the arithmetic unit 10. I11 and I12 in FIG. 5B indicate that the pixel is off, and I13 is the value when the density is to be reduced. Indicates a pixel to be turned off. When the control command 11 indicates that the density of the high-density region is to be reduced by one pixel, the arithmetic unit 10 reads the patterns sent one after another from the image memory 8 and obtains the pattern shown in FIG. In this case, the pixel I13 to be turned off next is turned off. In this way, it is possible to reduce the density of the high density area while keeping the image memory.

As described above, printing can be performed by changing the density of an arbitrary density area of an arbitrary color.

[0022]

As described above, according to the present invention, the threshold value of the dither matrix is made rewritable using a rewritable memory, so that the color correction using the dither matrix can be changed quickly. Can do it. Further, the gradation can be improved by combining a matrix for each color of the dither matrix with a plurality of basic matrices. Further, by adjusting the output of the image memory according to the contents of the dither matrix using the arithmetic unit, there is an effect that the density of an arbitrary color can be changed without changing the image memory.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a first embodiment of the present invention.

FIG. 2 is a configuration diagram of a second embodiment of the present invention.

FIG. 3 is a configuration diagram of a third embodiment of the present invention.

FIG. 4 is a diagram for explaining the contents of a dither matrix and the contents of an image memory which are input to the calculation unit shown in FIG. 3 when increasing the density of a low density area.

FIG. 5 is a diagram for explaining the contents of a dither matrix and the contents of an image memory which are input to the calculation unit shown in FIG. 3 when the density of the high density area is reduced.

[Explanation of symbols]

 2 Input threshold value 4 Output threshold value 5 Input image data 7 Comparison result output 9 Printing section

Claims (2)

(57) [Claims] 1. A color correction method for a color printer for printing by outputting the contents of the image memory to the printing section by the gradation processing method using a dither method, roughness of the linear input threshold
Corrected by a predetermined correction formula, output as an integer
That has a correcting unit, given the input threshold, the memory of the dither matrix for each color through the correcting section, 該Me
The output threshold value, which is the output of the memory, is compared with the input image data.
The comparison result binarized by the comparison unit is stored in the image memo.
A color correction method for a color printer , wherein a rewritable memory is used as the memory. 2. The color correction of a color printer according to claim 1.
The method comprises the steps of: providing a dark space between the image memory and the printing unit;
Connected to a computing unit for changing the degree,
The output of the dither matrix and the density specified by the user
Specific concentration range generated based on the density directive
Control command to increase or decrease the concentration of
Adjust the output of the image memory based on the
A color correction method for a color printer.