JPS59125173A - Recording method of gradation color - Google Patents

Abstract

PURPOSE:To display color with high accuracy for the gradation recording of comparatively high density by setting different order to the picture element of a picture element matrix for each recorded color. CONSTITUTION:The analog density signals of R, G and B which are read by a color scanner SCN are applied to an RGB/YMCK converter to be converted and quantized into each component of Y, M, C, and K and impressed to each digital comparator. The digital comparators compare those density data with the order of corresponding picture elements stored in an FOM. Then the output level is set at 1 (recording level) when the order of the corresponding picture elements is smaller than the density data. This output is impressed to a minimum value detector 10, and the order data are compared with each other for the colors which delivered those data. The color of the smallest order is defined as the recording level with other colors defined as the non-recording levels to output chrominance signals Y, M, C and K.

Description

Detailed Description of the Invention ■Technical Field The present invention relates to gradation recording in which gradation is expressed by recording the number of pixels corresponding to the gradation in a pixel matrix composed of a plurality of pixels, and in particular, The present invention relates to gradation color recording that performs color expression by recording a plurality of colors in one pixel matrix.

■Prior art In this type of recording, for example, a recording dot pattern (recording dot pattern in a predetermined number of pixel matrices) corresponding to the color density is assigned to the recording of each color, and the pattern is selected according to the color density instruction. to record the print.

According to this recording method, desired gradation recording can be performed in low-density and medium-density color gradation recording and all gradation recording in monochromatic recording.

However, in color recording where more than one color is recorded in the same matrix, it is possible to simply print a number of pixels from 0 to k (k is the number of pixels in the matrix) depending on the input level (a degree) of each color. In relatively high-density recording, multiple colors overlap in the same pixel. For example, when the three colors yellow, magenta, and cyan are all at their highest densities, the three colors of ink will be printed in an overlapping manner. In such a case, it is inevitable that the image quality, that is, the accuracy of expressed colors, will decline. Actually, yellow (Y), magenta (M)
and cyan (C) In the case of a color expressed by three colors of dora 1-, at least a part of each dora 1- is black (B).
This type of inconvenience can be eliminated by replacing the color with 1-, but in the case of colors expressed with any two colors, blanks cannot be used, so even if this method is used, the image quality cannot be improved. .

(1) Purpose of the Invention The object of the present invention is to express colors with high precision even in gradation color recording with relatively high density.

■Configuration When recording using multiple basic colors, if the recording pattern determined according to the gradation in each matrix is set to a different predetermined pattern for each color, if the recording density is relatively low, No overlap occurs. Also, when the printing density is high and the colors 1- and 2 overlap, depending on the type of ink, it may be better to record only one of the overlapping colors.
Image quality may be better than when colors are layered.

Therefore, if the image quality deteriorates significantly due to overlapping of multiple colors, set the recording pattern so that multiple colors do not overlap as much as possible at low density, and if overlapping occurs, record one of the multiple colors. By doing so, the image quality can be improved.

Hereinafter, the present invention will be described in detail with reference to the drawings.

In FIG. 1, the present invention is implemented in one embodiment! The color scanner SCN reads an image while main-scanning and sub-scanning a predetermined document, and prints out the three primary colors R (red) and G (green). ) and B (blue) respectively.The RG13/YMCK converter converts the RGB signals from the color scanner SCN into Y (yellow) 9M.
The color components of (magenta), C (cyan) and K (black) are converted and the respective densities are quantized and output from a digital (I output.RGB/YM, CA converter output). Talented Y, ~1. Each color signal of C and K is
tzo7I+, decita/[/ comparison W CP I, (
T; P 2 , ' CP 3 j', ; and cr'
4.

Read-only memories (ROMs) Rl, R2, R3 and R4 each store a predetermined address corresponding to each pixel constituting the pixel matrix, and the order of the hδ pixel.

In this embodiment, one pixel 71-1 is 16 pixels gQ -C4iυ made up of AA-DD as shown in FIG.
Each pixel has a density ranking for each basic color of y, M, c, and K as shown in Figures 3a, 3b, 3c, and 3d. It is set. This data is read-only memory R,1,R2
, R3 and R4.

That is, for example, for yellow Y, pixels A and A have a rank of 1. CC has a rank of 2. Rank 3 for CA
...... is set, and when the Y density is 1 (density range is 0 to 16), yellow is recorded only in pixel AA, as shown in Figure 4a, and similarly the Y density is When the density is 2, pixels AA and CC are applied as shown in Figure 4b, and when the density is 3, pixels AΔ and CC are applied as shown in Figure 4c.
Yellow is recorded in and CA, respectively. The same applies to other colors.

Therefore, for example, if the density of yellow Y is 4 and the density of cyan C is
If the number of pixels is 13, if recording is performed using the signal as it is, yellow Y and cyanino C will overlap in pixel AC, as shown in FIG. RG B/
By passing the output of the Y CMΔ converter to the subsequent circuit, only either Y or C is recorded in the above case.

That is, in this embodiment, when a signal for recording multiple colors is applied to the same pixel, the 3a
The lowest ranked color (lowest numerical value) shown in Figures 3D to 3D is set to the recording level, and the other colors are set to the non-recording level.

The explanation will be given by returning to FIG. 1 again. A1-res counter CO receives clock pulses output from color scanner SCN in response to main scanning and sub-scanning.
It is determined which one of ΔΔ to ■D in FIG. 2 the scanned pixel at that time corresponds to. , this result is applied to the addressing terminals of the read-only memories R1-R.1. In other words, the read-only memories R1 to R4 receive the designation of the positions 71 to 71 corresponding to the constantly scanned pixels and output the density ranking data corresponding to the designated pixels. The magnitude of this density rank data and the degree data from the RG B / Y M CK converter is determined by a digital comparator (T, Pl~()).
I) compared with lI.

For example, to explain yellow Y with reference to FIG. 3a, if the density data from the RGB/YMCA converter is 5, then at the timing when pixel AA is being scanned, the corresponding pixel's rank is 1 and higher than 5. Since the voltage ratio is also small, the output level of the ratio converters C and PI becomes 1 (recording level), and at the timing of scanning pixels BΔ, CA and DA, the non-recording L//<le (9>5) and the recording level (3 ≦
5) and non-recording level (II>5).

The outputs of the digital comparators CPI to CP4 are applied to the minimum value detector 10 and the signal selection circuit 20.

The minimum value detector 10 includes read-only memories R1 to R4.
Ranking data for each color is applied from .

The minimum value detector 10 compares the ranking data of the colors outputted from the digital comparators CPI to CP4 whose numbers (noted @/non-recorded) are at the 1 (recorded) level, and Color signals Y, M, C, and K are output in which the color with the lowest rank is set to a recording level, and the others are set to a non-recording level. This signal is applied to the input terminal B of the multiplexer MPX of the signal selection circuit 20, and the digital comparator CPI
The direct signal from ~CP 4 is sent to the multiplexer MI)
It is applied to input terminal A of X.

The adder ADD adds the output signals (numeric values) of the digital comparators CI)1 to CP4, and the digital comparator cp5 compares the added output with a constant 1. If the addition output is 1 or less, that is, the colors do not overlap for the same pixel, the digital comparator CP5 sets the output to a low level "0" and selects the input terminal A of the multiplexer MPX, and the addition output is 2. In other words, when there is an instruction to record multiple colors for the same pixel, the output is set to a high level "1" and the MPX manually selects the output. The direct signals from the digital comparators CPI to CP4 or the signal from the minimum value detector 10 are selected by the multiplexer MPX and outputted as recording i size signals to the recording (=J size) circuits for each color.

Therefore, in the example of Fig. 5 (the density of Y is 4, the density of C is 13)
), at the scanning timing of the pixel AC, the output levels of the digital comparators CI) ] □ to OP4 are respectively 1.0. ] and 0, the output of adder ADD becomes 2, and multiplexer MPX selects input terminal B. At this time, read-only memories R1 and R3 are
Since the values 4 and 13 are output respectively, the minimum value detector 10 outputs a recording signal for yellow Y which outputs 4 as 1 (recording level) and other colors as 0 (non-recording level). , this number 46 is selectively outputted by multiplexer MPX. Therefore, in the example of FIG. 5, yellow Y is recorded in pixel AC, and cyan C is not recorded.

Considering the error in this case, for cyan, the density of 13 pixels is recorded as 12 pixels, so the error is about -7%, but this overlap occurs only in part of the entire image. In addition, since the error with respect to the composite color expressed by Y, M, and C becomes smaller, the error is not so large in reality. Furthermore, if we reverse this (Fig. 5) and record only cyan C in pixel AC, the density error of only yellow is -25%, and the overall color error becomes quite large. I understand that. Therefore, by preferentially recording colors with lower density rankings as in this embodiment, errors can be made relatively small.

Next, another embodiment (2) of implementing the present invention will be explained.

FIG. 6 shows a recording signal generation device implementing one embodiment of the present invention. Color scanner SCN, RGB/YCMA converter, address counter CO2 read-only memory R1-
The configuration and operation of R4, digital comparison register C1'1 to CP4, and multiplexer MPX are the same as in the previous embodiment.
It is. Priority registers PRI, PR2, PR3 and P
R4 corresponds to the recording colors Y, C, M, and (2), respectively, and stores their respective priorities.

The priority control circuit 30 has a priority register PRI in advance.

Priorities 312 degrees 1 and 0 are stored in PR2, PR3, and PR4. If multiple colors do not overlap in the same pixel, select input A of multiplexer MPX, and if multiple colors overlap in the same pixel, select input B of multiplexer MPX and do the following: works.

In other words, read out the priorities stored in the priority registers (two or more from PRL to PR4) associated with the color that will become the recording level (1), and select the one with the highest priority (larger numerical value) among them. Multiplexer MP sends a recording activation signal that sets the corresponding color to recording level and other colors to non-recording level.
It is output to the input terminal I3 of X. Then, the contents of the priority register PRn corresponding to the color set to the recording level are set to the lowest level (0), and the contents of the registers storing data with a lower priority than the contents of the register PRn before updating are sequentially stored. , update to have a higher priority.

In other words, the contents of the register are changed as shown in Table 1 below.

Table 1 Therefore, as in the above embodiment, when recording of multiple colors is instructed, only one color ((highest i4 priority) among them is recorded; When this is done, the priority order is sequentially changed, so even if the same pattern is consecutive, a situation where only a single color is preferentially recorded does not occur.

In other words, according to this, even if there are many cases where multiple colors overlap in the same pixel, different colors are recorded sequentially, so
For the entire image, color errors are averaged out to improve image quality.

■Effects As described above, according to the present invention, only one color is always recorded in the same pixel (dot), so there is no deterioration in image quality due to color overlap.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a schematic configuration of a recording signal generating device implementing one embodiment of the present invention. FIG. 2 is a plan view showing the arrangement of each pixel in a pixel matrix composed of a plurality of pixels. 3a, 3b, 3c, and 3d are plan views showing the density order of yellow, magenta, cyan, and black of each pixel constituting one pixel 71 helix in the example. Figures 4a, 4b and 4c show 1 recorded when the density for yellow was 1.2 and 3 respectively.
FIG. 3 is a plan view showing one pixel matrix pattern. FIG. 5 is a plan view showing a pixel pattern recorded in one pixel matrix when the yellow density is 4 and the cyan density is 13. FIG. 6 is a block diagram of a recording signal generator implementing another embodiment of the present invention. 10: Minimum value detector 20: Signal selection circuit 30: Priority control circuit CPI, CF2. CF2. CF2. CF2: Digital comparator I, R2, R3, R4: Read-only memory RP]
,,RP2. RP3. RP4: Priority register SCN:
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Claims (1)

[Claims] (]) In gradation color recording in which each of a plurality of colors is recorded in a predetermined number of pixels according to the gradation in each pixel 71 helix composed of a plurality of pixels; pixel matrix A gradation system in which a different ranking is set for each recording color for each pixel in Color recording\ Recording method. (2) For each pixel in the pixel matrix, set a fixed order for each color in association with the gradation, and when there is a recording instruction for multiple colors to be engraved on the same pixel, the density for that pixel is set. The gradation color recording method according to claim 1, wherein a color having a low fixed rank is recorded. (3) For each pixel in the pixel matrix, set a different priority for each recording color, and when multiple colors are instructed to record for the same pixel, only the highest priority color is assigned to the corresponding pixel. 2. The gradation color recording method according to claim 1, wherein the ranking of each color with respect to the pixel is set such that the highest ranking is set to the lowest ranking and the other colors are set in order of higher ranking.