JPH01314087A - Color signal converter - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Applications] The present invention provides a color method that converts or corrects a plurality of input color signals representing colors into a desired output color signal using a function according to a color space region. The present invention relates to a signal conversion device, and particularly to a color signal conversion device that prevents local color differences and false contours from occurring.

[Prior Art] FIG. 2 is a block diagram showing a conventional color signal conversion device for converting complementary color signals into primary color signals, as described in, for example, Japanese Patent Application No. 62-332535.

In the figure, W (white), Y (yellow), Gr (green) and C
cyan) is a complementary color input color signal, and (1) is a pseudo three primary color signal R based on input color signals W, Y, Gr and C.
1 (red), Gl (green), and Bl (blue); (2) is a selection unit that generates a selection signal P according to the color space area based on the pseudo three primary color signals R1, G1, and [31]; This is a signal generation section.

(3) is a function table in which a plurality of functions (usually consisting of a matrix) for converting color signals from complementary colors to primary colors are stored corresponding to each color space region, and the selection signal P
(4) outputs primary color output color signals R (red), G (green) and This is a conversion unit that calculates B (blue).

Next, the operation of the conventional color signal conversion device shown in FIG. 2 will be explained. First, the calculation unit (1) performs calculations on the input color signals W, Y, Gr, and C based on the relationship between the complementary colors and the three primary colors, R1=W-C GI=Gr [11=W-Y , the selection signal generation unit <2) outputs the pseudo three primary color signals R1, Gl and B1.
1 and B1, the colors indicated by the input color signals W, Y, Gr and C are divided into five color space regions SI to S5, S,
= R, 1>Glf”l R1≧Bll”IW<WkS
,=G1≧R11”lG1≧BlnW<WkS,=B1
>R1>GlnW<Wk S4=B1>Gl≧R1f”IW<WkS, =W≧Wk It outputs a selection signal P indicating which one it belongs to.

However, Wk is a threshold value for white determination.

Next, the function table (3) selects the function F corresponding to the selection signal P from among the functions defined for each color space region and outputs it to the conversion unit (4). The converter (4) performs calculations according to the function F on the input color signals W, Y, Gr, and C, and outputs desired three primary color signals R1G and B.

[Problems to be Solved by the Invention] As described above, the conventional color signal conversion device selects one function F depending on the color space region, so the color near the boundary of the color space region is different from the input color. Signals W, Y, Gr and C
Therefore, when converting an input color signal from an image with smooth color changes, the selected function changes in the middle of the image, resulting in a different function being selected. The output color signal R, which is determined by
There is a problem in that the G and B values change suddenly, resulting in a sudden color change that does not exist in the original image, that is, a false contour occurs.

Furthermore, even if the color of the image is uniform and the input color signal is monochromatic, a slight change in the input color signal due to noise etc. will change the selected function, causing the color to change locally and creating false contours. There was a problem that occurred.

The present invention was made to solve the above-mentioned problems, and it is an object of the present invention to provide a color signal conversion device that can accurately express the color continuity or color pattern of an original image.

[Means for Solving the Problems] A color signal conversion device according to the present invention includes a selection signal generation unit for selecting from a function table a plurality of functions to be applied to a calculation for a color indicated by an input color signal; A plurality of calculation units each perform calculations based on a plurality of selected functions, and an output calculation unit that calculates an output color signal based on the plurality of calculation results obtained from these calculation units and the color feature signal of the input color signal. It is equipped with the following.

[Operation] In the present invention, all functions corresponding to color space regions to which the input color signal may belong are selected, taking into consideration the color characteristics of the input color signal and the influence of noise, and the obtained multiple calculation results are Find the output color signal.

[Example] Hereinafter, an example of the present invention will be described with reference to the drawings. 1st
The figure is a block diagram showing an embodiment of the present invention, where X is an input color signal consisting of, for example, W, Y, Gr, and C;
is an output color signal consisting of R, G and B, for example.

(12) is a selection signal P of a plurality of functions to be applied to the calculation based on the color characteristics determined from the input color signal
A selection signal generation unit that outputs ~P++, (13) a function table storing a plurality of (n) functions F corresponding to color space regions and ~Fn, (14,) to (14n) each function F
One calculation section (15) is used to perform calculations corresponding to each of calculation sections (141) to (14n) and the calculation results Zl to Zn obtained from each calculation section (141) to (14n) and the selection signal generation section (12). This is an output calculation unit that calculates an output color signal Z based on the color feature signal T.

Next, the operation of the embodiment of the present invention shown in FIG. 1 will be explained.

First, the color space region representing the color characteristics is divided into n parts, and the functions F1 to Fn corresponding to each part are found and the function table (1
3) is stored in advance.

The selection signal generation unit (12) determines to which region in the color space the color indicated by the input color signal X belongs, based on the magnitude relationship of each element W, Y, Gr, and C of the input color signal X. and outputs a selection signal Pi of a function Fi (1≦i≦n) to be calculated.

At this time, for example, the selection signal Pi is set to 1 for the function Fi to be calculated, the selection signal Pj is set to O for the function Fj that is not calculated, and the color area determined based on the input color signal Each function corresponding to a color space region within a predetermined distance from the center is subjected to calculation. In addition, the color space region on which the calculation is to be performed is determined, taking into consideration the fluctuations caused when ±α noise signals are superimposed on the input color signal X.

The function table (13) outputs each function Fi corresponding to the color space region designated by the selection signal Pi to the calculation unit (14i). The calculation unit (14i) calculates Zi=Fi− for the input color signal X according to each function Fi.
X and outputs the output color signal Z(r(,G,B) and the same signal system computation result Zi(Ri, Gi, Bi).

At*, the output calculation unit (15) performs a summation operation using i=1 to n for each element R;, Gi, and Bi on the operation result Zi, and obtains R=ΣK Ri Ri/ΣKRi G=ΣKqiGi /ΣKqi B−ΣK(1iBi/ΣKBi Calculate the output color signal Z. However, KHi, Kq
i and i are weighted coefficients for each element for each calculation result Zi. Note that the calculation result Zj cannot be obtained from the calculation unit (14j) of the function Fj that is not symmetrical, and based on the color feature signal T at that time, the coefficients K nj, K qj, and Kej for the calculation result Zj are Set to O. Therefore, if KHi=Kqi=Koi=1, the output color signal Z (R, G, B) becomes the simple average value of each calculation result Z j (Ri, G i, B i). Usually, the values of each coefficient KRi, Kqi and KBi are:
For example, since it is set to a function (corresponding to the reciprocal) of the color indicated by the input color signal X and the distance to each color space area, a continuous output color signal Z can be obtained even for colors near the boundaries of each spatial area.

In this way, by determining the output color signal Z using the calculation results obtained based on multiple functions, even for the input color signal χ of an image with smooth color changes,
The function used in the calculation does not change suddenly, and an intermediate layer of several types of functions is included, so that smooth color changes can be expressed in the output color signal Z as well.

Furthermore, for a monochromatic input color signal X such as - near the boundary of the color space region, the probability of the color space region to which it can belong within the superimposition range of the noise signal of ±α is determined by each coefficient K Ri , K qi
and KBi, so that false contours due to local color changes do not occur.

In the above embodiment, n calculation units (141) to (14n) were provided corresponding to n functions F, to Fn, but 1
When the number of functions Fi selected for the calculation is limited to Il (≦n) or less, the calculation units (14,) to (
14m). In this case, the function table (1
3) will output only the selected function Fi.

In addition, the criteria for determining the selection signal Pi in the selection signal generation section (12) and the values of the coefficients KRi, Kqi, and KBi used in the calculation in the output calculation section (15) can be looked up in advance, either individually or in combination. By storing and preparing the output color signal in an up-table, the arithmetic processing of the output color signal and the signal Z becomes faster and more accurate, and there is a high degree of freedom in the five-circuit configuration (thereby, there is an advantage that the entire apparatus can be simplified).

Furthermore, the input color signal X was set to W, Y, Gr, and C, and the output color signal 2 was set to R, G, and B, but the number of elements of each of the input color signal X and output color signal Z was 3 and 4, respectively.
You can select any number, not just one. In addition, the input color signal It goes without saying that the same effect can be achieved even when applied to the case of conversion to a system.

[Effects of the Invention] As described above, according to the present invention, there is provided a selection signal generation unit for selecting from a function table a plurality of functions to be applied to a calculation for one color indicated by an input color signal; and an output calculation section that calculates an output color signal based on the plurality of calculation results obtained from these calculation parts and the color feature signal of the input color signal. In preparation, select all functions corresponding to color space regions that may belong, taking into account the color characteristics of the input color signal and the influence of noise, and calculate the output color signal from the obtained multiple calculation results. Therefore, it is possible to obtain a color signal conversion device that does not generate false contours even for input color signals of images having smooth color changes or monochromatic images near the boundaries of color space regions.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is a block diagram showing a conventional color signal conversion device. (12)...Selection signal generation unit (13)...Function table (14,) to (14n)...Calculation unit (15)
...Output calculation section X...Input color signal Z...
Output color signal P, ~Pn...selection signal F, ~F
n...Function 2, ~Zn...Computation result T...Color feature signal plane In the drawings, the same reference numerals indicate the same or equivalent parts. ＼be1, Indication of the case Patent Application No. 143667 of 19882, Name of the invention Color signal converter 3, Person making the amendment Relationship to the case Patent applicant address 2-2-3 Marunouchi, Chiyoda-ku, Tokyo Name (601) Mitsubishi Electric Corporation Representative Moriya Shiki 4, Agent address 4th floor, Marunouchi Building, 2-4-1 Marunouchi, Chiyoda-ku, Tokyo Telephone (216) 5811 [Representative] 5, Subject of amendment ( 1) Column 6 for detailed explanation of the invention in the specification Contents of amendment (1) “Pseudo contour '' are corrected as ``pseudo contours, spots, etc.''. (2) "Not calculated" on page 7, line 11 of the specification is corrected to "not applied to calculations." (3) Page 7, line 15 and lines 16-17 of the specification, and
"Symmetry" in line 13 of page 8 is corrected to "object". (4) “Used for calculation” on page 9, line 9 of the specification is amended to “used for calculation”. (5) On page 9, line 11 of the specification, ``to become,'' is amended to ``to become, therefore,''. (6) Amend "Also to Z" on page 9, line 12 of the specification to "by Z."

Claims (1)

[Claims] It has a function table storing a plurality of functions corresponding to each color space region, and for a plurality of input color signals indicating colors,
In a color signal conversion device that converts or corrects a desired output color signal using a function according to the color space region, a plurality of functions to be applied to a calculation for a color indicated by the input color signal are selected from the function table. a selection signal generation unit for selection; a plurality of calculation units each performing calculations based on the selected plurality of functions; and a plurality of calculation results obtained from these calculation units and a color feature signal of the input color signal. A color signal conversion device comprising: an output calculation section that calculates the output color signal based on the following.