JPS61257071A - Color picture signal processing unit - Google Patents

Abstract

PURPOSE:To dispense with the dedicated ROM for black generation and to compact the size by allotting a data tables for black generation to some of masking tables for recording other than black. CONSTITUTION:8-bit color input signals R, G, B are converted into 6-bit color signals C, M, Y by a logarithm conversion table ROM 6 and inputted to masking tables ROM 8C, 8M, 8Y, for each color. Cyan density signal C' obtained from the table 8C is masking-processed according to the functions of inputs C, M, Y, and since six bits are enough to maintain total gradation, the remaining two bits can be used for black density value. Similarly, two output bits of Magenta and yellow masking tables 8M, 8Y are also used for the black density value. The black density data BK can be expressed as a function of C, M, Y. Obtained C', M', Y' are converted into drive voltage Vc, Vm, Vy and Vbk respectively by density voltage conversion tables 10C, 10M, 10Y and 10BK, which drive ink jet heads 12C, 12M, 12Y and 12BK.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a color image signal processing device that obtains color signals for a plurality of recording colors including black from a plurality of input color signals.

<Prior Art> Conventionally, this type of color image signal processing device has required a masking section for correcting asymmetric color components such as ink and developer, and a black generation section for generating black component data.

An example of a conventional processing circuit is shown in FIG. In FIG. 2, 2C, 2M.

2Y is a masking table for cyan, magenta, and yellow each composed of a ROM, and 4 is a black generation ROM that generates a black component.

The 8-bit input color signals C, M, and Y are input to the tables 2G, 2M, and 2Y for each color and the black generation ROM 4, where asymmetric color removal is performed, and each bit signal σ, M, and Y of the recording color is ' is obtained. Further, the generating section 4 obtains a 6-bit black signal BK.

As described above, the conventional technology requires a dedicated ROM for black generation. Also, to create gradation for recording, usually 6
Although 64 bits and 64 gradations are sufficient, many commercially available ROMs are 8 bits, and 2 bits are wasted for 1 address input.

OBJECTIVES The present invention aims to eliminate the drawbacks of the prior art as described above and to provide a compact color image signal processing device that does not require a dedicated ROM for black generation.

<Example> Hereinafter, an example in which the present invention is applied to an inkjet color printer will be described in detail with reference to the drawings.

FIG. 2 shows a signal processing circuit of the inkjet color printer of this embodiment.

In the figure, 6 is a logarithmic conversion table, and 8C98M and 8Y are masking tables for cyan, magenta, and yellow, respectively, IOC, IOM, and IOY.

10BK is a density-voltage conversion ROM that converts digital density values into inkjet head drive voltage values Vc, VM, Vy, Vex, 12C, 12M, 12Y
, 12BK is an inkjet head of each color, 14C, 1
4M, 14Y, and 14BK indicate droplets of each color, respectively.

The operation will be explained below.

The 8-bit human color signals R, G, and B are converted into 6-bit color signals C, M, and Y by a logarithmic conversion table 6, respectively.

This is C, M that corresponds to the address in advance using the RGB digital value as the address.

This can be achieved by writing Y in advance. The obtained signals C, M, and Y are applied to masking tables 8C and 8C for each color, respectively.
Input to 8M and 8Y. The cyan masking table 8C will be explained.

The cyan density signal σ obtained from Table 8C is generally subjected to masking processing using a function of the inputs C, M, and Y. Therefore, you can use the C, M, and Y values as addresses and write the masking processing results as data at those addresses.
At this time, the signal C has the most influence on the cyan density signal σ, followed by M, and Y has the least influence, so the cyan signal C has all 6 bits, the magenta signal has the upper 5 bits, The yellow signal Y uses the upper 4 bits as an address to reduce the ROM capacity. Further, the ROM for the cyan masking table uses an 8-bit ROM as output data. Since 6 bits is sufficient for the cyan density signal σ, the remaining 2 bits are used as the black density value.

Similarly, the magenta and yellow masking tables 8M and 8Y use the output 2 bits as the black density value.

The black density value data BK is a function aarab cell of C, M, Y.
)+β (α, β are constants), or BK=-fog(0,3
0” to-c+ 0.59-10-N+ 0.11
・1O-Y) Illustrated for etc. Therefore, each masking table 8C, 8M.

Since the upper 4 bits of C, the upper 5 bits of M, and the upper 4 bits of Y are commonly input to 8Y, calculate in advance the 6 bits of black data when these are input, and then Cyan masking table 8C for the upper 2 bits
8M magenta masking table for the middle 2 bits.
, masking table 8Y with yellow for the lower 2 bits.
Store it in

With this configuration, there is no need to provide a dedicated black generating section.
Black density value BK and non-black recording density signals σ, M, Y'
can be obtained at the same time.

The obtained σ, M, Y', and BK are the drive voltage values vc and vM of the inkjet head, respectively, based on the density voltage conversion tables I OC, 10M, 10Y, and 10BK.

vY, v, and each inkjet head 12
Drives C, 12M, 12Y, and 12BK.

As described above, according to this embodiment, a dedicated table for black generation is omitted, and furthermore, all the output bit numbers of the masking table for recording colors other than black can be used, which is extremely advantageous.

Although this embodiment has been described using an inkjet printer as an example, the invention can be applied to various color printers such as electrophotographic printers, thermal printers, and thermal transfer printers.

Further, although black data is assigned to all masking tables other than black, it may be distributed to two masking tables.

Effects> As explained in detail above, the present invention distributes the data table for black generation to some of the masking tables for recording colors other than black, so there is no need for a dedicated ROM for black generation, resulting in a compact design. It is possible to provide a processing device that is

[Brief explanation of the drawing]

FIG. 1 is a signal processing circuit diagram of the inkjet color printer of this embodiment, and FIG. 2 is a conventional processing circuit diagram. In the figure, 8C, 8M, and 8Y are cyan, macenta, and
Showing the yellow masking table.

Claims (1)

[Claims] In order to obtain color signals for a plurality of recording colors other than black from a plurality of input color signals, a masking table is provided for each recording color other than black, and some of the plurality of masking tables contain data for generation. A color image signal processing device characterized by having distributed tables.