JPS63147643A - Color image processing apparatus - Google Patents

Abstract

PURPOSE:To reduce the memory capacity of a circuit, by a method wherein the higher rank bit of an input digital color image signal is used as an input address to obtain color correction data by a masking table, and this output data is added to the above-mentioned image signal. CONSTITUTION:8-bit input digital color signals Y, M, C are inputted to a color successive converting circuit 1 and an 8-bit color successive signal CSS and a 2-bit color discriminating signal CID showing how many number of colors are outputted presently are outputted. The signals at every 6-bit of the input digital color signals and the 2-bit signal CID are inputted to a masking table 2 in which 8-bit output data re preliminarily stored to determine an address and 8-bit output data are outputted to be added to the previous signals CSS by an adder 3 to output a signal CSS'. The memory capacity of the memory apparatus for the masking table can be reduced and, at the same time, accurate data can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a color image processing apparatus, and more particularly to a color image processing apparatus that performs masking processing on a digital color image signal by referring to a table.

(Prior Art) Masking processing circuits that remove unnecessary colors from digital image signals using a table reference method have been known.

FIG. 3 shows such a conventional masking processing circuit.

Here, 5 is a masking table, which is an input digital color image signal (input color signal) Y in a fixed storage device etc.
Output data Y', M' from which unnecessary colors have been removed corresponding to the density combinations of , M, and C.

Co is stored in advance in the form of a table, and the corresponding output data Y', M', C' is read out and outputted according to the combination address of Y, M, and C of the human color signal during image processing. The masking table 5 in this figure is based on a human color signal Y, for example.

M and C are each 8 bits per pixel, output data Y"
, M', and C' also show the case of 8 bits per pixel.

(Problem to be Solved by the Invention) However, in order to obtain such output data with the conventional device, in the case of the masking table 5 described above, the combined address of input color signals Y, M, and C is 224, and the output data Each of Y', M', and C' is 1 byte (8 bits) and 3
Since it is a color output, the storage capacity is 3 x 224 bytes ±
It requires 48 megabytes. As described above, in order to perform accurate masking processing by referring to a table in the conventional device, a huge amount of storage capacity is required.

SUMMARY OF THE INVENTION An object of the present invention is to provide a color image processing device that can eliminate the above-mentioned drawbacks, reduce the storage capacity of a masking table storage device, and at the same time obtain accurate masking data.

[Means for solving problems]

In order to achieve such an object, the present invention provides a color image processing device that performs masking processing on an N-bit digital color image signal separated into a plurality of colors. However, N
> M) as a manual address to obtain output color correction data for each color; and an arithmetic circuit that obtains masking data by adding the output color correction data of the table reference circuit and an N-bit digital color image signal. It is characterized by having the following.

(For I) According to the present invention, a table reference circuit (masking table) is provided for obtaining color correction data by using the upper M bits of an N-bit human-powered digital color image signal as a human-powered address,
Since the output data obtained from this circuit and the above-mentioned human-powered digital color image signal are added to obtain color-corrected masking data, the storage capacity of the table reference circuit can be significantly reduced, and high-quality color Images can also be obtained.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the drawings.

First, before specifically explaining this embodiment, the basic structural concept of a masking processing circuit according to this embodiment, which will be described later, will be explained.

A first-order masking equation for performing masking processing can generally be expressed in the following form.

(Here, an, βn, ln (n=1.2°3) are constants) In the above formula (1), the constant 1α11 is usually the constant 1α21
, 1α31. Similarly, 1β21
is 1β1 I, 1β31, 1γ31 is 1γ11
, 1γ21. In other words, it can be expressed as . Moreover, α1. β2. γ3>1 (3). Therefore, equation (1) can be rewritten as follows.

Furthermore, equation (4) becomes. In equation (5), Y contributes the most to the value of Y', and the contribution of (α□°Y+α2M+α3C) is relatively small. The same can be said of the formulas for Mo and Co. Therefore, in equation (5), the human color signal Y in parentheses on the right side.

The accuracy of M and C is manually colored No. 48 Y and M outside the parentheses.

Even if the accuracy is slightly lower than that of C, the output data Y°.

The deterioration in accuracy given to M' and C is sufficiently small and poses no practical problem.

Therefore, in this embodiment, as described later, a masking table is provided that stores output data corresponding to the data in parentheses on the right side of equation (5), and the number of reference bits from the human color signals Y, M, and C is reduced. By referring to the masking table using a low-precision input address and adding the resulting data to the original high-precision input color signals Y, M, and C, the color correction data on the left side of equation (5) is obtained. Y', M'
, C'. Note that for convenience of explanation, this example was explained using a first-order masking equation, but
The idea is similar to the case of masking equations of quadratic or higher order, and the present invention can be applied.

FIG. 1 shows a circuit configuration of a main part of an embodiment of the present invention. In this figure, 1 is a color sequential conversion circuit, which converts 8-bit digital color signals Y, M, C manually input in parallel to yl, M, , C1°K, Y2 . M2. C2, ni2・
This is a circuit that converts color sequential signals for each pixel in the order . 2 is ROM (read only memory) or RA
This is a masking table as described above, which is composed of memories such as M (random access memory), and stores in advance 8-bit output data corresponding to the data in parentheses on the right side of equation (5).

3 adds the 8-bit color sequential signal C55 (Y, M, C) obtained from the color sequential conversion circuit 1 and the 8-bit output data obtained from the masking table 2, and outputs the addition result as a digital color signal. This is an adder (arithmetic circuit) that outputs signals t and ss'.

The address of the above-mentioned masking table 2 is determined by the upper 6 bits of each of the input digital color signals Y, M, and C and 2 bits of the color identification signal 1jD. 8-bit output data is obtained from the masking table 2 by this address.

That is, (α1′Y+α2M+α,
C), (βI Y+β2 ゛ M+β3 C).

The value (γ, Y+γ2M+γ3°C) is obtained as the output data of the masking table 2.

The storage capacity of the masking table 2 in this embodiment is as follows:
For each color, 28 bytes = 256 bytes are required, so for 3 colors, 256 and 3 bytes = 7688
Becomes a part-time worker. On the other hand, as explained in the conventional example,
In conventional technology, masking processing using 8-bit manual input for each color and 8-bit output requires 48 megabytes (48 x 106 bytes) of storage capacity for the masking table.
In this embodiment, only 768 bytes (768 x 103 bytes) are required, so the storage capacity can be reduced to about 1760 compared to the conventional method.

The 8-bit data for each color obtained from the masking table 2 is sequentially added to the input 8-bit data C5S of the same color as the color obtained from the masking table 2 in the adder 3, and the final 8-bit color correction is performed. The data is output as data css'. That is, according to this embodiment, the process shown by equation (5) is performed, and high-precision digital image data Y',
M' and C' are obtained. In this way, according to this embodiment, the memory capacity of the masking table 2 can be reduced and highly accurate color correction data can be obtained. In fact, as a result of carrying out this example, it was confirmed that a color image having the same quality as the color image reproduced by the conventional technique shown in FIG. 2 could be obtained.

In the embodiment of the present invention described above, one masking table was provided for three colors and the colors were processed sequentially. However, the present invention is not limited to this, and parallel processing is performed using different masker tables and adders for each color. Also good.

An example is shown in FIG. In this figure, 4 is a masking table that obtains 8 bits of parallel output for 6 bits of manual input for each color, and (α1°Y + α2M +
α3C), (β1Y+β2°M+β3C), (γ1゛Y
+γ2M+γ3'C) can be obtained at the same time. Each data obtained from this masking table 4 is added to the input 8-bit digital image signals Y, M, and C in corresponding adders 6Y, 6L, and 6G, respectively, and finally color correction data Y after masking processing is obtained. ', M', C' 0
In the case of this embodiment as well, the storage capacity of the masking table 4 is the same as in the embodiment shown in FIG. 1, except that the number of adders is slightly increased.

〔Effect of the invention〕

As explained above, according to the present invention, a table reference circuit (masking table) for obtaining color correction data using the upper M bits of an N-bit input digital color image signal as a manual address is provided, and output data obtained from this circuit is provided. Since color-corrected masking data is obtained by adding the input digital color image signal and the above-mentioned input digital color image signal, the storage capacity of the table reference circuit can be significantly reduced, and a high-quality color image can also be obtained.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a circuit configuration of one embodiment of the present invention, FIG. 2 is a block diagram showing a circuit configuration of another embodiment of the invention, and FIG. 3 is a block diagram showing a conventional circuit. 1... Color sequential conversion circuit, 2... Masking table, 3... Adder, 4.5... Masking table. > Σ Q Y Main plane 0 i ya 0 pods direction i row 0 block diagram Fig. 2

Claims (1)

[Scope of Claims] In a color image processing device that performs masking processing on an N-bit digital color image signal separated into a plurality of colors, the upper M bits of the N-bit digital color image signal (where N> a table reference circuit that obtains output color correction data for each color using M) as an input address; and an operation that obtains masking data by adding the output color correction data of the table reference circuit and the N-bit digital color image signal. A color image processing device characterized by comprising a circuit.