JPH10285413A - Color converter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a color converter in which number of signal lines is effectively decreased and can be miniaturized without significant reduction in the input/output speeds, in comparison with a conventional color converter that for adapting a parallel input/parallel output method. SOLUTION: This color converter 110 has a 2-byte input signal line 401 and a 2-byte output signal line 501 for receiving an RGB color values in total of 3 bytes and to provide an output of a CMYK color value in total of 4 bytes. The R, G color values are received from the input signal line 401 for a first clock period in parallel, and the B color value is received in parallel for a succeeding clock period. A color conversion circuit 101 converts the received RGB color values into the CMYK color value. The C color value and the M color value are outputted from the output signal line 501 for a first clock period in parallel, and the Y color value and K color value are outputted in parallel for a succeeding clock period.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color conversion apparatus for converting a color value of one color system into a color value of another color system.

[0002]

2. Description of the Related Art As a color system for handling colors as numerical values, RGB, CMY and CMYK systems are well known. Image input devices such as image scanners,
An application program for image processing, an output device of a soft copy of an image such as a display, and the like often handle an image using RGB color values. On the other hand, many output devices for hard copy of images, such as printers, perform printing based on CMY or CMYK color values. Therefore, when an RGB color image created by an R host computer is to be printed by a printer, a process of converting RGB color values into CMY or CMYK color values is required. This conversion process is called “color conversion”.

A conventional color converter (typically an "IC") employs an input / output type of "RGB parallel input / CMYK parallel output". That is, as shown in FIG. 1, the conventional color conversion IC 100
In each period, the RGB color value 200 of one pixel is input in parallel, and the CMYK color value 300 of one pixel is output in parallel. Since the value of each color component is typically one byte word, a conventional color conversion IC
Represents the input signal line 400 of 3 bytes of RGB three colors and CMY
A 4-byte output signal line 500 of K4 color, that is, a data signal line of 7 bytes in total is provided.

[0004]

As described above, the conventional color conversion IC has a large number of data signal lines of 7 bytes. Further, since control signal lines such as a clock CLK, an input synchronization signal ISYNC, and an output synchronization signal OSSYNC are required, a total of about 60 signal lines are provided. Inevitably, the size of the IC package becomes considerably large.

It is natural that the smaller the IC size is, the better. In order to reduce the size of the IC, it is necessary to reduce the number of signal lines. Then, "RGB parallel input
It is conceivable to adopt an input / output method of “CMYK serial output”. Then, since the number of output signal lines is reduced to 1 byte, the total data signal line becomes 4 bytes. In addition, "R
GB serial input / CMYK parallel output ”,
It is also conceivable to reduce the number of input signal lines to 1 byte to make a total of 5 bytes. In any case, the number of signal lines can be reduced from 2/3 of the conventional signal line to nearly 1/2.

However, in the former case, only one color component value can be output in one clock cycle, so four clock cycles are required to output a CMYK color value of one pixel. Also, in the latter case, only one color component value can be input in one clock cycle, so three clock cycles are required to input the RGB color value of one pixel. Thus, the input / output speed is lower than that of the conventional one.
低下 or ３. As a result, in these systems, the cost of greatly reducing the input / output speed is greater than the advantage of reducing the number of signal lines.

Accordingly, an object of the present invention is to provide a color conversion apparatus of the conventional "parallel input / parallel output" type,
It is an object of the present invention to provide a color conversion device that can effectively reduce the number of signal lines without significantly lowering the input / output speed, and thus can be made more compact.

[0008]

According to a first aspect of the present invention, there is provided a color conversion device for converting an input color value having M components into an output color value having N components.
Is an integer of 2 or more less than M, L is an integer of 2 or more less than N, and A is 1 as a quotient of M / K when M is divisible by K, and 1 when M is not divisible.
, And B is N when N is divisible by L.
When the quotient of / L is not divisible, and when the value is obtained by adding 1 to the integer quotient of N / L, the following components are provided. That is,
An input signal line capable of parallel input of A component values of input color values, an output signal line capable of parallel output of B component values of output color values, and input color values divided into K times Input means for receiving from a signal line, color conversion means for receiving an input color value from the input means and converting it to an output color value, and receiving an output color value from the color conversion means and dividing it into L times Output means for outputting the output signal to the output signal line.

As a specific example, in an embodiment described later, the input color value is an RGB color value, and the output color value is a CMY color value.
Since it is a K color value, M = 3 and N = 4, and since K = 2 and L = 2, A = B = 2. Therefore, this embodiment has an input signal line that can input two color values in parallel and an output signal line that can output two color values in parallel, and outputs RGB color values twice, for example, RG and B. And input at two clock cycles,
The converted CMYK color values are output twice in two clock cycles, such as CM and YK.

As described above, according to the present invention, the input / output speed is reduced to 1 / K or 1 / L as compared with the conventional "parallel input / parallel output" color conversion apparatus, but the number of data signal lines is reduced. Also decreases to almost (K + L) / 2KL. K
When L and L are close to each other, especially when K = L, generally good results are obtained. In this case, the input / output speed is 1 / K
However, the number of data signal lines also decreases to nearly 1 / K. In other words, the decrease in the input / output speed does not become much greater than the decrease in the number of signal lines, and the two rates are almost equal. Therefore, the size of the apparatus can be reduced without greatly reducing the speed.

[0011] A color conversion apparatus according to a second aspect of the present invention comprises:
An input color value having M components is converted into an output color value having a different color system.
If A is divisible by K, then A is M
If the quotient of / K is not divisible and the integer quotient of M / K is incremented by 1, an input signal line capable of parallel input of A component values of the input color value and an input color value of K
An input unit receives the input color value from the input signal line in different times, and a color conversion unit receives the input color value from the input unit and converts the input color value into an output color value.

A color conversion device according to a third aspect of the present invention comprises:
An input color value is converted into an output color value having N components having different colorimetric systems.
B is N when N is divisible by L
If the quotient of / L is not divisible, and if it is a value obtained by adding 1 to the integer quotient of N / L, an output signal line capable of outputting B component values of the output color value in parallel and an input color value are received. A color conversion means for converting the output color value into an output color value; and an output means for receiving the output color value from the color conversion means and outputting the output color value to the output signal line in L times.

In the color conversion device according to the second aspect of the present invention, the number of input signal lines is reduced to 1 / K, in the device according to the third aspect, the number of output signal lines is reduced to 1 / L, and The input / output speed can be kept down to 1 / K or 1 / L. These color conversion devices are, for example, a conversion device between a color value composed of a plurality of color components and a color value composed of a single component (monochrome value) without greatly reducing the input / output speed. This helps to effectively reduce the data signal lines for color component color values.

[0014]

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

FIG. 2 is a block diagram of a color conversion apparatus according to an embodiment of the present invention. FIG. 3 shows this color conversion device 1.
10 is a timing chart showing the operation of Example No. 10.

As shown in FIG. 2, the color conversion device 110
It has an input signal line 401 for inputting one byte of RGB color value 201 for each color per pixel, and an output signal line 501 for outputting a CMYK color value 301 of one byte for each color. The input signal line 401 is 2 bytes,
One byte (hereinafter referred to as an RB signal line) is assigned to input of an R color value and a B color value, and the other byte (hereinafter referred to as a G signal line) is assigned to an input of a G color value. The output signal line 501 is also 2 bytes, of which 1 byte (hereinafter referred to as a CY signal line) outputs a C color value and a Y color value, and the other 1 byte (hereinafter referred to as an MK signal line) as an M color value. And K color value output. In addition to these data signal lines 401 and 501,
Control signal lines 701, 801 and 901 for inputting the bit clock CLK and the input synchronization signal ISYNC and outputting the output synchronization signal OSSYNC are also provided. Therefore,
The total number of signal lines of this color conversion device 110 is 4 bytes + 3 bits = 35, and the number of signal lines is 1/2 that of the conventional device 100 (about 60 total signal lines) shown in FIG.
It is decreasing near. Note that the input synchronization signal ISYNC and the output synchronization signal OSSYNC are signals having twice the cycle of the clock CLK (see FIG. 3).

The input and output of color values by the data signal lines 401 and 501 are performed in synchronization with the clock CLK (see FIG. 3). However, for the input signal line 401, the R color value and the G color value are input at the same clock cycle (parallel input), but the RG color value and the B color value are alternately input (serial input) at different clock cycles. You. That is, R and G color values are input in the first first clock cycle, and B color values are input in the next second clock cycle, and this operation is repeated. Also, the output signal line 50
Regarding 1, the C color value and the M color value, and the Y color value and the K color value are output at the same clock cycle (parallel output), but the CM color value and the YK color value are alternately output at different clock cycles. (Serial output). That is, a CM color value is output in the first clock cycle, a YK color value is output in the next second clock cycle, and this operation is repeated. Therefore, one pixel RGB
It takes two clock cycles to input a color value and output a CMYK color value. This means that the input / output speed is １ ／ as compared with the conventional device 100 shown in FIG.

A color conversion circuit 1 is provided inside the color conversion device 110.
01. This color conversion circuit 101 has RGB input terminals R ′, G ′, B ′ and CMYK output terminals C ′, M ′, Y ′,
K ′, and inputs and outputs color values in a “parallel input / parallel output” system. That is, the RGB color values are fetched in parallel from the input terminals R ', G', B 'and
The CMYK color values are converted into YK color values, and the CMYK color values are output in parallel from output terminals C ′, M ′, Y ′, and K ′. The color conversion device 110 uses the input synchronization signal I
The synchronization is performed in synchronization with SYNC, and an output synchronization signal OSSYNC is output in synchronization with the output operation.

Input signal line 401 and R of color conversion circuit 101
There is a latch 106 between the GB inputs R ′, G ′, B ′. The latch 106 operates in synchronization with the input synchronization signal 801 to take in the R and G color values coming from the input signal line 401 at the above-described first clock period, and to read this RG color value for the next two clock periods. And then applied to the RG input terminals R ′ and G ′ of the color conversion circuit 110. Also,
The color value coming from the RB signal line in the input signal line 401 is always applied to the B input terminal B ′ of the color conversion device 110.

The CMYK output terminals C ', M',
A latch 10 is provided between Y ′ and K ′ and the output signal line 501.
7 and a selector 108. The color conversion circuit 101
In the clock cycle, the CMYK color value is output and the output synchronization signal OSSYNC is output. The latch 107 fetches the Y color value and the K color value from the color conversion circuit 101 in synchronization with the output synchronization signal OSSYNC, holds the Y color value and the K color value during the next two clock cycles, and applies the values to the selector 108. The selector 108 operates in synchronization with the output synchronization signal OSSYNC, and at the time of the first clock cycle, selects the C and M color values output from the color conversion circuit 101 and outputs them to the output signal line 501, At the next second clock cycle, the Y and K color values from the latch 107 are selected and output to the output signal line 501.

Next, the operation of the color conversion circuit 101 configured as described above will be described in detail with reference to FIG.

As shown, the input synchronization signal ISYNC goes high in the first clock cycle and goes low in the next second clock cycle. When the input synchronization signal ISYNC is at the high level (first clock cycle), the R color signal and the G color signal of one pixel are input in parallel from the input signal line 401, and then the input synchronization signal ISYNC is at the low level. At the time (second clock cycle), the B color signal of the same pixel is input (at this time, the data on the G input signal line is null data).

The latch 106 receives the input synchronization signal ISYNC.
At the falling edge of R, the R color signal and the G color signal on the input signal line 401 are fetched, held for the next two clock cycles, and applied to the RG input terminals R 'and G' of the color conversion circuit 101. Therefore, when the input synchronization signal ISYNC is at a low level (second clock cycle), the RGB color values are aligned and applied to the input terminals R ′, G ′, B ′ of the color conversion circuit 101 in parallel. At this time, the color conversion circuit 101 takes in the RGB color values.

The color conversion circuit 101 converts the captured RGB color values into CMYK color values. This conversion process requires a time corresponding to a predetermined number of clock cycles (for simplicity, FIG. 3 shows one clock cycle). The converted CMYK color values of one pixel appear at the output terminals C ′, M ′, Y ′, and K ′ of the color conversion circuit 101 in two clock cycles in parallel. In synchronization with this, the output synchronization signal OSYN
C is also output.

The latch 107 outputs an output synchronizing signal OSSYNC.
At the falling edge of Y, the Y color value and the K color value appearing at the YK output terminals Y ′ and K are fetched, and during the following two clock cycles,
The YK color value is held and added to the selector 108.
When the output synchronization signal OSSYNC is at a high level (first clock cycle), the selector 108 selects the C color value and the M color value appearing at the CM output terminals C ′ and M ′ of the color conversion circuit 101, and At the low level (second clock cycle), the Y color value and the K color value coming from the latch 107 are selected. Accordingly, the C and M color values of one pixel are output in parallel to the output signal line 501 in the first clock cycle, and the Y and K color values of the same pixel are output in parallel in the next second clock cycle. Is output.

As can be seen from the above description, FIGS.
In the embodiment shown in FIG. 1, the input / output speed is reduced to half as compared with the conventional color conversion device shown in FIG. 1, but the number of signal lines is also reduced to almost 1/2, so that the color conversion IC It is easy to reduce the size. Nowadays, since the clock speed of the circuit is being increasingly increased, it is considered that it is relatively easy to compensate for the decrease in the input / output speed of about 1/2 by increasing the clock speed. Therefore, there is a great benefit that the number of signal lines has been reduced to nearly half and miniaturization has been facilitated.

The above embodiment is an exemplification for explanation, and is not intended to limit the scope of the present invention only thereto.
The present invention can be implemented in various different modes without being limited to only the specific configuration and operation described above. For example, the present invention is applicable not only to color conversion from RGB to CMYK, but also to color conversion in the reverse direction, color conversion between RGB and CMY, and color conversion between other color systems. Applicable.

[Brief description of the drawings]

FIG. 1 is a block diagram of a conventional color conversion apparatus.

FIG. 2 is a block diagram of a color conversion apparatus according to an embodiment of the present invention.

FIG. 3 is an operation timing chart of the color conversion apparatus according to one embodiment of the present invention.

[Explanation of symbols]

 110 Color conversion device 101 Color conversion circuit 106, 107 Latch 108 Selector 201 Input RGB color value 301 Output CMYK color value 401 Input signal line 501 Output signal line 701 Clock signal line 801 Input synchronization signal line 901 Output synchronization signal line

Claims (6)

[Claims] 1. A color conversion apparatus for converting an input color value having M components into an output color value having N components, wherein K is an integer of 2 or more smaller than M, and L is smaller than N. A is an integer greater than or equal to 2, A is the quotient of M / K when M is divisible by K, and 1 is added to the integer quotient of M / K when M is not divisible, and B is N / when N is divisible by L. When the quotient of L is not divisible, and when a value obtained by adding 1 to the integer quotient of N / L, an input signal line capable of parallel inputting A component values of the input color values; An output signal line capable of outputting the B component values in parallel, input means for dividing the input color value into K times from the input signal line, and receiving the input color value from the input means. Color conversion means for converting to the output color value In response to the output color values from the color conversion unit, which color conversion device and output means for outputting to the output signal line is divided into L times. 2. The color conversion device according to claim 1, wherein K = L. 3. The color conversion apparatus according to claim 1, wherein one of the input color value and the output color value is an RGB color value, and the other is a CMYK color value or a CMY color value. 4. The color conversion device according to claim 1, wherein K or L is 2. 5. A color conversion device for converting an input color value having M components into an output color value having a different color system, wherein K is an integer of 2 or more smaller than M; An input signal line capable of parallel inputting A component values of the input color values when the quotient of M / K is divisible, and a value obtained by adding 1 to the integer quotient of M / K otherwise. Input means for receiving an input color value from the input signal line in K times; and color conversion means for receiving the input color value from the input means and converting the input color value to the output color value apparatus. 6. A color conversion apparatus for converting an input color value into an output color value having N components having different colorimetric systems.
Is an integer of 2 or more smaller than N, and B is the quotient of N / L when N is divisible by L, and the value obtained by adding 1 to the integer quotient of N / L when N is not divisible, the output color value An output signal line capable of outputting the B component values in parallel, color conversion means for receiving the input color value and converting the input color value to the output color value, and receiving the output color value from the color conversion means. Output means for dividing the output signal line into L times and outputting it to the output signal line.