JPS6163182A - Gamma converting circuit - Google Patents

Abstract

PURPOSE:To rewrite freely implementated gamma conversion and to read independently the converted data which are written in RAM by installing a rewriting input means which inputs a parameter to rewrite the implemetated gamma converting data. CONSTITUTION:ROM3 and input devices 4 and 5 are connected to CPU2 of a converting device, CPU2 removes a parameter to gamma-convert picture data inputted from ROM3 to input data lines 14-17, and the first data selector 6 and a data selector 7 are controlled. By the control, an address bus 18 of CPU2 and an address line 9 of RAM1 are connected. Further, CPU2 controls the second selector 8 and connects a data bus 22 and a data line 12 and the data gamma-converted at CPU2 are successively written in RAM1. Next, CPU2 changes over selectors 7 and 8, a control line 21 is connected to a control line 11, a data line 12 is connected to an output data line 13 and freely gamma- corrected data are outputted.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a gamma conversion circuit that linearly or nonlinearly converts image data, and particularly relates to a gamma conversion circuit that nonlinearly converts color image data.

[Prior art and its problems]

Conventionally, when performing Gamma conversion of image data, etc. with this type of circuit, random access memory (RAM) or read-only memory (ROM) is used, the above image data is input to the address input of these, and the RAM or read-only memory (ROM) is used. ROM
RAM according to the gamma conversion table written in
Alternatively, it is configured to obtain desired gamma-converted image data from the data output of the ROM. Also, RAM
When performing gamma conversion using By configuring it so that a desired gamma conversion table can be stored in the RAM, the RAM can be used as a conversion table for image data.

However, in order to create a gamma curve, an arbitrary gamma curve is created by complexly combining input devices such as digitizers, which increases the cost. In addition, there is a method in which a desired gamma conversion table is prepared in advance to be written in the RAM and a selection is made from among the tables, but this is very inconvenient as it is necessary to select it each time image data is input. Furthermore, to check the conversion characteristics of data using the created gamma curve, either read out the given gamma curve and make an analogy from that value, or provide data or a test pattern to understand the input characteristics of the gamma curve conversion device. However, the conversion characteristics had to be investigated and there were problems with operability.

[Purpose of the invention]

The present invention has been made in consideration of the above points, and automatically reads each gamma conversion data created by the gamma conversion data creation means into a random access memory according to a designated address, and applies desired gamma conversion to the image data. An object of the present invention is to provide a gamma conversion circuit that can arbitrarily rewrite gamma conversion data created as necessary.

〔Example〕

FIG. 1 is a block diagram of a gamma conversion device showing an embodiment of the present invention, in which 1 is a RAM (group RAM) having a 10-bit address line and an 8-bit data line, and 2 is a gamma conversion data generator. The CPU serving as the means controls the connected address lines or data lines. 3 is the RAMI
4.5 is an input device that sends parameters or data for rewriting the created gamma conversion data to the RAMI, and corresponds to the rewrite parameter input means. 6 is a first data selector that selects image data according to the identification signal and sends the address value sent by the CPU 2 to the address input of the RAMI; 7 is a data selector that switches control lines; 8 is a gamma signal sent from the CPU 2; This is a second data selector that switches between conversion data and output data from RAM1. 9 is the RAM1
A 10-bit address line or data line is connected to the 7 address inputs of the first data selector 6 and RA.
This is an 8-bit address line or data line that connects MI, and uses the lower 8 bits of address line 9. Reference numeral 11 denotes a 2-bit address line or control line selected by the data selector 7, and the upper 2 bits of the address line 9 are used.

12 is an 8-bit data line connected to the data input terminal of the RAMI, and 13 is an 8-bit output data line. 14 to 17 are four sets of input data lines that form a color image, for example, a yellow (Y) signal, a magenta (M) signal,
Cyan (C) signal.

A black (K) signal corresponds to each input data line 14-17. 18 is an address bus consisting of 10 bits, of which the lower 8 bits are sent to the Azores bus 19, and the upper 2 bits are sent to the Azores bus 19.
Bits are respectively used for address bus 20. 21
is a data control line which acts on the first data selector 6 to select one of the input data lines 14 to 17, and acts on the data selector 7 to connect the address line 11.

22 is a data bus of the CPU 2, which is connected to the second data selector 8. Note that the contents of ROM3 may be data that creates an initial state in RAM1, or eight data that determine gamma curves for gamma converting color image data input from input data lines 14 to 17 by the function of CPU2, which will be described later. (A set of two parameters corresponds to each input data line 14 to 17).

Next, the operation will be explained.

First, when the power is turned on, the CPU 2 initializes peripheral devices (not shown) according to a program using commonly used means. Next, the CPU 2 retrieves from the ROM 3 a first parameter set ay and by for gamma converting the image data input to the input data line 14. The CPU 2 controls the first data selector 6 to control the address bus 19, the address line 1o, and the data selector 7 to connect the address bus 2o and the address line 11, and connects the address bus 18 of the CPU 2 to the address input of the RAM 1. do.

In general, the CPU 2 controls the second data selector 8 to connect the data bus 22 to the data input of the RAMI via the data line 12. Next, the CPU 2 sets the address bus 20 and the address line 11 made up of the upper two bits of the address bus 18 made up of 10 bits to "0", and sets the address line 11 to "0".
9, that is, the address of address line 10 is 0 to 255.
The gamma conversion data corresponding to the gamma curve calculated by the CPU 2 by the method described later using the first parameter set ay and by is sent via the data bus 22, that is, the data line 12, while Then, the CPU 2 retrieves the second set of parameters am and bm for gamma converting the image data input to the input data line 15 from the ROM 3, and writes them to the lower 256 bytes of the RAM 1 using the method used. And set the address line 11 to "°l".

As before, gamma conversion data is written in the next 256 bytes of RAMI. Subsequently, the CPU 2 retrieves a third set of parameters aC and bc for gamma converting the image data input to the input data line 16 from the ROM 3, sets the address line 20 and the address line 11 to °°2'', and performs the above-mentioned process. Similarly, gamma conversion data is written into the next 256 bytes of RAM 1. Next, CPU 2 retrieves the fourth parameter set ak and bk for gamma conversion of the image data input to input data line 17 from ROM 3, and addresses The line 20 and the address line 11 are set to "3" degrees, and gamma conversion data is written to the next 256 bytes of RAM 1 as described above.Next, the CPU 2 switches the data selector 7 and connects the control line 21 to the control line 11. Second
The data selector 8 is switched to connect the data line 12 to the output data line 13. As a result, RAM1 is
The gamma conversion data of the RAM 1 determined by the image data signals Y, M, and C input from the input data lines 14 to 17 and the identification signal input from the control line 21 is sent to the output data line 13. Output. In this way, the identification signal acts on the first data selector 6 to select one of the input data lines 14 to 17, becomes the upper address of RAMI, and becomes one of the written gamma conversion tables (gamma conversion table). data collection). Therefore, for example, when the identification signal input to the control line 21 is "1'", the image data signal M is connected to the data line 10 from the input data line 15, and the image data signal M"°
0 to 255" is on the actual data line 9 °"256 to 5 t
t'', the data is converted by the second created gamma conversion table in RAM 1, and sent to output data line 13.

However, the gamma conversion does not always produce favorable results for all the signals on the input data lines 14-17. For example, 512 in RAMI corresponding to C image
If you want to rewrite the third gamma conversion table stored at addresses ~767, input the set of parameters ac', bc' for creating that curve from the input device 4.5.
When input, the CPU 2 controls the first data selector 6, the data selector 7, and the second data selector 8, and as described above, the address bus 19 and the data line 1o, the address bus 2o and the control line 11, and the data bus 22 and the data Connect the wires 12 respectively. Then, the address bus 2o is set to "2", the address bus 19 is sequentially changed from 0 to 255, and the address data 512 to 767 are input to the address input terminal of the RAMI into the lower 8 bits of the data line 9. Parameter ac' input from device 4.5
.

Gamma conversion data 512 to 767 forming a gamma curve calculated by the CPU 2 from bc' are sequentially written to the data input terminal of the RAM 1. When this writing is completed, data selector 7.8 connects control line 21.11 to data line 12 and output data line 13, respectively. Note that the normally required chip enable end of RAM1, lead/
light end.

The control lines, the chip enable end of the ROM 3, the address and lead lines, and the address line 1 interrupt line of the input device 4.5 are connected by known techniques and are not particularly shown.

Next, the work of rewriting the gamma conversion table will be explained.

When arbitrary parameters ai (shown in FIG. 2) and bi (shown in FIG. 3) are input from the input devices 4 and 5, the equation of the following straight line is determined, and Y=ai (X-
bi ) ”・(1) Next, the CPU 2 calculates gamma conversion data from d=o to 255 from the following equation (2) using Y determined by the above equation (1). is a Gaussian symbol.

However, Yi = a (Xi-b) forb≦Xi
≦(255/a)+b Yi=Of Xi<b Yi=255 for Xi>(255/a)+bYi=-
ab forX i < O and
b<.

shall be.

FIG. 4 shows an example of gamma conversion data O~255 calculated based on equations (1) and (2) for parameters a=2 and b=63. However, in the second equation, n=9.

5 and 6 are gamma curves similarly calculated according to the above procedure, where the solid line indicates Yi and the broken line indicates Table
(d), and the horizontal axis is the table number (d) 0 to 2
55, and the vertical axis represents the gamma conversion value.

Next, a method of outputting the contents of the gamma conversion table (Table(d)) created in the RAMI as a test mode will be explained.

The CPU 2 controls the first data selector 6 and the data selector 7 to substantially connect the address bus 18 to the address 9 of the RAM 1. Subsequently, the CPU 2 controls the second data selector 8 to connect the RAMI data line 12 to the output data line 13. Thereafter, the CPU 2 outputs all address data from 0 to 1023 to the address bus 18 by ordinary means. At that time, the output data line 13 has a RAMI
All contents are sent.

Next, the gamma conversion table creation and output preparation operations will be described with reference to the flowchart of FIG.

Note that 5L-316 represents each step.

First, the CPU 2 controls the first data selector 6 to connect the address line 19 and the data line 10 (S
L) Similarly, the data selector 7 is controlled to connect the address bus 20 and the address line 11 (S2), and the second data selector 8 is similarly controlled to connect the data bus 22 and the data line 12 (S3). Next, the CPU 2 sends 0'' to the address bus 20 (S4). Next, it is determined whether "4" is sent to the address bus 2o (S5), and if No, the parameter set ay is sent from the ROM 3. and by (S6), and the CPU 2 sends "0" to the address bus 19 (S7).Next, it is determined whether the address value of the address bus 19 is "256" (S8), and if No As mentioned above, CPU2
calculates the gamma conversion data 0 to 255 (S9) and sends the gamma conversion data 0 to 255 to the data bus 22.
10) Write this gamma conversion data 0 to 255 from the data line 12 to the data input terminal of RAM1 (31
1), then set the address value of address 19 to “°1″
The value is incremented and the process returns to step S8 (S l 2).

On the other hand, if the determination in step S8 is YES, the address value of the address bus 20 is incremented by 1° and the process returns to step S5 (S l 3).
If the judgment is YES, the process moves to the output preparation operation of the created gamma conversion data, and first, the control of the first data selector 6 is transferred to the control line 21 (S l 4), and the CPU 2 switches the data selector 7 and controls it. line 21 and address line 11
(S15), the second data selector 8 is switched to connect the data line 12 and the output data line 13 (S16), and the output preparation is completed.

Next, the gamma conversion table rewriting operation will be described with reference to FIG. Note that S21 to S31 represent each step.

First, the CPU 2 controls the first data selector 6 to connect the address line 19 and the data line 10 (52
1) Similarly, the data selector 7 is controlled to connect the address bus 20 and the address line 11 (322), and the second data selector 8 is similarly controlled to connect the data bus 22 and the data line 12 (S23). , followed by CPU2
The parameter ac' for forming a new gamma curve
and bc' are taken in from the input devices 4 and 5 (S24
), then an identification signal input from the control line 21, for example, "Set the address bus 2o according to the 2-pass signal 525".
), sends "0'' to address bus 19 (326)
. Subsequently, the address value of address bus 19 becomes '256.
327), and if No, the parameters ac' and bc taken in step s24 are
528), the CPU 2 calculates the gamma conversion data "256" according to
9), Newly write the gamma conversion data calculated in step 328 to addresses 512 to 767 in RAMI (
S30). Next, the address value of the address bus 19 is incremented by "°1" and the process returns to step S27 (S
31). On the other hand, if YES in step S27, the write operation ends.

Next, the pseudo signal generation operation will be explained with reference to the flowchart of FIG. Note that S41 to S347 represent each step.

First, the CPU 2 controls the first data selector 6 to connect the address bus 19 and the data line 1Q (541),
Similarly, the data selector 7 is controlled to connect the address bus 20 and the control line 11 (542), and the second data selector 8 is also controlled to connect the data line 12 (542).
and the output data line 13 (S43). Next, the CPU 2 sends "0" to the address bus 18 to prepare for sending a pseudo signal (S44),
8 is "1024" (545), and if NO, the gamma conversion data "0 to 1024" stored in the RAM 1 are sequentially output to the data line 13 via the data line 12 ( 346). Next, the address value of the address bus 18 is incremented by "1" and the process returns to step 545 (S47).
By repeating steps 5 to S47, input data lines 14 to 17
A pseudo signal (gamma conversion data) is output from the RAMI as if color image data were sent. On the other hand, if the determination in step S45 is YES, the pseudo signal generation operation is ended.

〔Effect of the invention〕

As explained above, since the present invention is provided with a rewrite parameter input means for inputting parameters for rewriting the created gamma conversion data, the created gamma conversion data can be rewritten at will. In addition, according to the address value generated by the gamma conversion data creation means,
Since the gamma conversion data written in the AM can be independently read out, it has the advantage that it can be used as a pseudo signal generator for gamma conversion data.

[Brief explanation of drawings]

FIG. 1 is a configuration block diagram of a gamma conversion circuit showing an embodiment of the present invention, FIGS. 2 and 3 are diagrams showing input parameters for rewriting gamma conversion data, and FIG. 4 is a diagram showing calculated values of gamma conversion data. Figures 5 and 6 are waveform diagrams showing gamma conversion data characteristics; Figure 7 is a flowchart illustrating gamma conversion table creation and output preparation operations;
FIG. 8 is a flowchart for explaining the gamma conversion table rewriting operation, and FIG. 9 is a flowchart for explaining the pseudo signal generation operation. In the figure, 1 is a RAM, 2 is a CPU, 3 is a ROM, 4.5 is an input device, 6 is a first data selector, 7 is a data selector, 8 is a second data selector, 9.1o, 11 are address lines, 12 is a data line, 13 is an output data line, 14-1
7 is an input data line, 18, 19.20 is an address bus,
21 is a control line, and 22 is a data bus. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5

Claims (2)

[Claims] (1) In accordance with the identification signal added to each image data signal, the parameters for creating gamma conversion data are read from the nonvolatile memory, and the gamma conversion data is created by the gamma conversion data creation means in accordance with the parameters. To rewrite the created gamma conversion data in a gamma conversion circuit that writes data to the data input of a random access memory and performs desired gamma conversion on each image data input to the address input of this random access memory. 1. A gamma conversion circuit comprising a rewriting parameter input means for inputting a parameter. (2) If no parameters are input from the rewriting parameter input means, the parameters stored in the nonvolatile memory are read out.
) The gamma conversion circuit described in section 2.