JPH01109967A - Color converter - Google Patents

Abstract

PURPOSE:To reduce the capacity of a ROM and conversion error by resolving R, G, B picture signals into plural sets so that bits of the same digit belong the same set, applying partial color conversion for each set and adding the result to printed color. CONSTITUTION:A picture signal inputted to an input terminal 1 is given to an address terminal of ROMs 3, 4, 5. On the other hand, the picture signal given to an input terminal 2 is given to an address terminal of ROMs 6, 7, 8. Since a desired local color conversion data corresponding to each address is stored in the ROMs 3-8, a partial color conversion data is obtained after a prescribed access time. Adders 9-11 add the data subject to color conversion by the printed color and printed color signals Y, M, C are outputted from an output terminal 12. In increasing the number of resolution, the input number of the adders is increased but the capacity of the ROM is saved. Thus, the capacity of the ROM is saved without degrading the accuracy.

Description

[Detailed description of the invention] [Industrial application field] This invention includes red, green, and blue (hereinafter referred to as rR, G).

The image signal consists of yellow and magenta.

The present invention relates to a color conversion device that converts print color signal data into three colors of cyan (hereinafter referred to as rY, M, and C) or four colors of Y, M, C, and black (hereinafter referred to as rKJ).

[Prior Art] Conventional color conversion devices of this type include, for example, Japanese Patent Laid-Open No. 58
There are those disclosed in Japanese Patent Application Laid-open No. 178355, Japanese Patent Application Laid-Open No. 60-220660, and the like.

The former.

However, it has the disadvantage that the desired color conversion result cannot be obtained and the conversion error is large.

In addition, the latter device prepares multiple matrix coefficients,
The conversion error is reduced by performing matrix calculation by adaptively selecting matrix coefficients to be used depending on the state of the pixel. However, this method also has the drawback that the conversion error becomes large at the switching boundary of the matrix coefficients. In other words, the best color conversion cannot be performed unless one matrix coefficient is prepared for each pixel.

FIG. 6 shows the conventional R that can perform the best color conversion.
FIG. 2 is a block circuit diagram of a color conversion device using OM table conversion. In the figure, (100) is a ROM, R, G
, B image quality code is input to the address terminal of the ROM (100), and the Y, M, and C printing signal data stored in advance at each address address is configured to perform color conversion by table conversion. There is.

Generally, when converting R, G, and B image quality codes into print color signal data, each of the R, G, and B image quality codes requires data of 6 bits or more for each pixel. Now, if this is 6 bits, the number of addresses per color is 218, and l
Y per address.

Since 1 byte (8 bits) is required for each of the three colors M and C, the total capacity of ROM (100) is 21”
X 3 X 8 terrorism, 3M bits.

[Problems to be Solved by the Invention] As described above, the conventional color conversion method using matrix calculation has a large conversion error and cannot obtain a printed image that is faithful to the original image. Does the color conversion method you used require a large ROM capacity? There were problems such as it being uneconomical.

The present invention was made to solve the above-mentioned problems, and it is an object of the present invention to provide a color conversion device using table conversion, which has a small conversion error and can reduce the capacity of a ROM.

[Means for Solving the Problems] The color conversion device according to the present invention converts R, G, and B image quality codes in which each pixel is composed of data of 6 bits or more into the same set of bits of the same order. It is equipped with means for decomposing into two or more sets according to their belonging, means for performing partial color conversion by table conversion for each separated set, and means for adding each partial color conversion data for each printing color. .

[Operation] The means for decomposing R, G, and B image quality codes in this invention is R
, G, B The bits of the same order of digits of the image quality code are included in the same set, and are decomposed into a plurality of sets. Further, the partial color conversion means performs partial color conversion into each print color signal data for each set. The adding means adds the partially color-converted data for each print color and outputs print signal data of three or four colors.

[Embodiment of the invention] FIG. 1 is a block circuit diagram of an embodiment of the invention.
) are image signals Ru and cu of the upper 3 bits of the 6-bit R, G, and B image quality signals, respectively.

nu is input to the terminal, (2) is the same terminal to which the lower 3 bits of image signals RL, GL, and BL are input.
(3) is the first ROM storing partial color conversion data yu for Ru, GU +BU, and (4) is the R
Partial color conversion data M for u, Gu, Bu
The second ROM in which IJ is stored, (5) is Ru,
The third ROM stores partial color conversion data Cu for GLI and BU, (8) is RL, Gl +B
The fourth section in which the partial color conversion data Y[ for L is stored
(7) is a fifth ROM in which color conversion data ML for RL + Gt + B1 is stored;
(8) is the sixth ROM in which partial color conversion data CL for RL + GL + BL is stored, and each RO
The number of addresses of M is 29=512. (9) is the first adder that performs the calculation Yυ0YL = Y and outputs the print color signal data Y, and (10) performs the calculation Mυ0ML = M and outputs the print color signal data M. The second adder, (
11) is a third adder that performs the calculation Cu + CI =c and outputs print color signal data C; (12) is an output terminal for print color signal data Y, M, and C;

Next, the operation will be explained. The image signals RU, Gυ, and BU input to the input terminal (1) are stored in the ROM (3), respectively.
Each address terminal 4 of ROM (4) and ROM (5)
Cloudy input.

On the other hand, the image signal RL + input to the input terminal (2)
GL + BL are each ROM (8).

It is input to each address terminal of ROM (?) and ROM (8). Since the desired partial color conversion data corresponding to each address is stored in ROM (3) to (8), after a predetermined access time, Yu,
Partial color conversion data of YL, Mu, ML, CU, and CL is obtained. Adder (9).

(10) and (11) are respectively y=yu +Y
,, M=MU + M 1 , (= (:υ+Ct
The addition operation is executed to output print color signal data Y, M, and C from the output terminal (12).

In this example, the number of addresses in each ROM is 512, and 1 byte = 8 bits is required per 51 addresses, so the total capacity of ROMs (3) to (8) is -
512 x 8 (bits) x 6 (pieces) = 24.578 bits. this is.

The capacity is 1/25B compared to the conventional example shown in FIG.

In the above embodiment, the R, G, and B image value codes are separated into two sets of upper 3 bits and lower 3 bits and partial color conversion is performed. Alternatively, partial color conversion may be performed by dividing into 6 bits each. FIG. 2 is a block circuit diagram of an embodiment in which the circuit is divided into three parts.

In the figure, (21) represents the image signal r5. ra
, gs , ga , bs , ba , the first ROM stores partial color conversion data Y2 , M2 , C2 , and (22) similarly contains intermediate 2-bit image signals r3 , r2 +g3 , l+ +b3 , b2
The second ROM (23) stores the partial color conversion data Y, , M, , C, for the lower 2 pit no image signals rI2 ro 9g+ + go +
Partial color conversion data Yo, M for b+ tbo
,.

The third ROM stores Co, and the number of addresses in each ROM is 26=64. (24) is Y2 + Y1
The first adder performs the calculation +Yo =Y and outputs the print color signal data Y, (25) is M2 +M1 +Mo
A second adder (2B) performs the calculation of =M and outputs print color signal data M, and (2B) represents a third adder that performs the calculation of C2+C1+Co =C and outputs print color signal data C.

In this embodiment as well, R, G
, B image values can be converted into Y, M, C printing color signal data. The total capacity of ROM required is
26 (address a) x 3 (color) x 8 (bit) x 3 (
number of decompositions) = 4, fi08 K bits. In other words, if the number of decompositions is increased, the number of inputs to the adder increases and the amount of eight codes increases, but the capacity of the ROM can be reduced.

In addition, the same structure can be used when the data is divided into 6 parts, and the total ROM capacity required in this case is 23 (number of addresses) x 3 (colors).
×8 (bits) ×6 (number of decompositions) = 1.152 K bits. However, in the case of 6-separation, the amount of hardware for the adder to add the 6 partial color conversion data increases, the addition time also increases, and it is necessary to decompose and re-add the 6 pieces of data. It is also necessary to consider the occurrence of addition errors due to processing. Therefore, ROM
The number of decompositions must be determined by taking into account conditions such as the capacity and amount of logic circuits, calculation time, and conversion accuracy.

FIG. 3 is a block circuit diagram of another embodiment with less conversion error, and the same reference numerals as in FIG. 1 indicate the same or corresponding components, respectively.

The seventh ROM (31) and the fourth adder (32) are newly added components. The ROM (31) receives the image signals Ru, cu IBU of the upper 3 bits of each 6-bit R, G, and B image value code at its address terminal, and outputs the image signal RL of the lower 3 bits of the image signal.

Output the corrected values X of GL and BL. The correction value X is.

Each correction value r of the image signal RL + GL + BL,
g.

b, and each correction value r, g, b is a polar sign indicating + and - (“+” indicates emphasis, “-” indicates decrease)
and a 3-bit numerical code, and an adder (
32) is R't = Rt + r.

The image signal R'L + of the lower 3 bits is corrected by executing the calculations GL = GL +g, Bt = B1 +b.
c6L, B11L as ROM (8), (7)
, output to the address terminal (8). Thereafter, partial color conversion and addition are performed in the same manner as in the embodiment shown in FIG. 1 to obtain print color signal data Y, M, and C.

The required capacity of ROM (31) in this example is:
Three types of 4-bit data are required per input address, and the total number of addresses is 29, so 29 X3X4=
8.144 Kbits.

However, since most ROMs have a byte structure (8 bits), if this is used, the number of bits will be 12.288.

On the other hand, the adder (32) can be implemented with 200 gates. In this way, in this embodiment, by slightly increasing the ROM capacity and adding hardware, it is possible to perform color corrections such as (1) correction of color conversion data according to combinations of pixel data, and (2) adjustment of memorized colors such as skin tones. This makes it possible to realize color conversion with smaller conversion errors.

In the embodiments described above, parallel configurations have been shown, but a series configuration can also be realized as shown in FIG.

In the figure, the same symbols as in FIG. 3 indicate the same components, and (41) is Ru IGU.

A selector that selects and outputs an image signal of lMl from two sets of image signals of BU, RL, GL, and BL, controlled by a SEL signal, (42) is table conversion data Y
U, MIJ, Cu, YL, ML, C
L and r.

Store g and b in their respective predetermined address positions and
OM, (43), (44) are ROM (42) (7
) The first step is to temporarily store output data. A second D-type flip-flop (hereinafter referred to as rDFFJ),
CLR signal, TI double signal T2 signal, SEL signal and B
The ANK signal is a control signal given from the outside to operate this embodiment.

Next, the operation of this embodiment will be explained. First, selector (4
1) is the input image signal R controlled by the SEL signal.
u, Gu, BU and RL, GL, BL
The image signal Rυ of the upper 3 bits is selected from among the two sets of .

Select and output GU and BU. At this time, D F
F (43) is set to OP by the CLR signal,
Correction value X is not output. The adder (32) receives the correction value X
Since , has not been input, Ru , G, .

Output the BU as is to the ROM (42).

The ROM (42) is sequentially switched by the BANK signal and receives the 9-bit image signal Ru input from the adder (32).
Using GU and BU as address signals, corrected values r, g, and b are sequentially output by table conversion.

D F F (43) are correction values r and g that are input sequentially.
.

b is temporarily stored at a predetermined position under the control of the T1 signal.

Next, the ROM (42) is controlled by the BANK signal and the Y
Perform table conversion of u to n F F (44) -
Remember when. Next, clear D F F (43) with C
It is canceled by the LR signal and the corrected values r, g, and b are output. Next, the selector (41) is switched by the SEL signal to output the signal RL*GL+BL of the lower three bits of the image signal to the adder (32), and the adder (32) stores the calculation result of BL+b in the ROM (42). ).

The ROM (42) outputs YL as specified by the BANK signal. The adder (45) adds this YL and D F F (
44), an addition operation of Y=Y of Yu stored at - time and Yu+Yt is performed, and print color signal data Y is output. Thereafter, the printing color signal data M and C are color-changed using the same procedure.

FIG. 5 shows an example of correspondence between the BANK structure and each data in the embodiment of FIG. 4. 2” = 512 addresses for each BANK, 29 x 9 (BA
NK number) x 8 (bits) = 38.884 bits is the capacity of the ROM (42) of this embodiment.

In the embodiment shown in FIG. 4, the selector (41) and the adder (
The configuration is such that the signal processing is executed in the order of 32).

In addition, input the image signals RL IGL and BL to one of the adders (32), and input the r, g, and b signals to the other to select the addition result! The configuration input to x(41) (
However, the Ru, GU, and BU signals may be input directly to the selector (41); in this case, the CLR signal is not required.

Although the above embodiment shows an example in which the image signals R, G, and B are composed of 6 bits each, the same effect can be obtained by applying the present invention even if the image signals are composed of 7 or 8 bits. It will be done.

Further, in the above embodiment, the case where color conversion is performed to print signal data of three colors Y, M, C, but for example, Y, M, C, K
This can be similarly applied to the case of color conversion to the four colors.

Further, the number of bits in each decomposed set does not have to be the same, and the decomposition may be performed such that each set is formed by, for example, the upper 2 bits and the lower 4 bits.

[Effects of the Invention] As described above, according to the present invention, R, G, and B image signals are decomposed into a plurality of sets such that bits of the same order of magnitude are included in the same set, and partial color conversion is performed for each set. The configuration is configured to obtain print signal data for three or four colors by adding each print signal data of the same color after conversion, so the ROM capacity required for conversion can be significantly reduced without sacrificing accuracy. There is an effect obtained by the conversion device.

[Brief explanation of the drawing]

1 to 4 are block circuit diagrams showing different embodiments of the present invention, FIG. 5 is a diagram showing the contents of the ROM in the embodiment of FIG. 4, and FIG. 6 is a configuration based on a conventional color conversion method. FIG. 2 is a block circuit diagram illustrating an example. (3), (4), (5), (8), (7), (8), (
21), (22), (23). (31)...ROM, (9), (10), (11
), (24), (25). (2B), (32), (45)...multiplier. In each figure, the same reference numerals indicate the same or corresponding parts.

Claims (2)

[Claims] (1) A means for dividing an R, G, and B image signal in which each pixel is composed of data of 6 or more bits into two or more sets such that bits of the same order of digits belong to the same set, and For each set, Y, M,
A color comprising means for performing partial color conversion on printing color signal data for three colors of C or four colors of Y, M, C, and K, and means for adding the obtained partial color conversion data for each printing color. conversion device. (2) The means for performing partial color conversion corrects the contents of the combination of bit sets of lower digits in correspondence with the combination of bit sets of upper digits, and removes discontinuity in color conversion or changes the partial color. Claim 1 configured to make a modification
Color conversion device described in Section 1.