JPH0722398B2 - Gamma conversion circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention creates gamma conversion data for converting the characteristics of a plurality of types of input image data, and creates each of the created gamma conversion data. The present invention relates to a gamma conversion circuit that can be changed to desired characteristics.

[Prior art and its problems]

Conventionally, when gamma conversion of image data etc. is performed by this type of circuit, random access memory (RAM) or read only memory (ROM) is used, and the image data is input to those address inputs, and RAM or ROM is used. According to the gamma conversion table written in, the RAM or ROM data output is configured to obtain gamma-converted desired image data. Also, when using RAM to perform gamma conversion, specify the RAM address as the input data line and C
Configured so that it can be switched with the PU address line,
In addition, by configuring the RAM data line so that it can be switched between the output data line and the CPU data line,
A desired gamma conversion table can be written in and the RAM can be used as a conversion table of image data.

However, in order to create a gamma curve, an arbitrary gamma curve is created by complicatedly combining input devices such as a digitizer, which results in high cost. Further, although a desired gamma conversion table to be written in the RAM is prepared in advance and there is one that can be selected, it is very inconvenient because it needs to be selected each time image data is input.

[Object of the Invention]

The present invention has been made in view of the above points, and writes gamma conversion data for converting the characteristics of a plurality of types of image data to be input into a memory to create the gamma conversion data, and to generate each gamma conversion data in the memory. By changing the data to the desired characteristics based on each input parameter,
An object of the present invention is to provide a gamma conversion circuit that can perform various image conversions on a plurality of types of input image data. Hereinafter, the present invention will be described with reference to the drawings.

〔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 10-bit address lines and 8-bit data lines, and 2 is a means for creating gamma-converted data. The connected CPU controls the connected address or data lines. 3 is a non-volatile memory (RO which sends out parameters or data for giving initial values to the RAM 1)
M), 4 and 5 are input devices for sending parameters for replacing the created gamma conversion data to RAM1. 6 is a first data selector for selecting the image data according to the identification signal and sending the address value sent by the CPU 2 to the address input of the RAM 1, 7 is a data selector for switching the control line, 8 is a gamma sent from the CPU 2. With converted data
It is a second data selector that switches between output data from RAM1. 9 is connected to the address input of the RAM1 10
A bit address line or data line, 10 is an 8-bit address line or data line connecting the first data selector 6 and the RAM 1, and the lower 8 bits of the address line 9 are used. Reference numeral 11 is a 2-bit address line or control line selected by the data selector 7, and uses the upper 2 bits of the address line 9. Reference numeral 12 is an 8-bit data line connected to the data input terminal of the RAM 1, and 13 is an 8-bit output data line (data line). 14 to 17 are four sets of input data lines forming a color image. For example, a yellow (Y) signal, a magenta (M) signal, a cyan (C) signal, and a black (K) signal are input to each input data line 14 to 17. It corresponds. Reference numeral 18 is an address bus (address line) composed of 10 bits, of which the lower 8 bits are used for the address bus (address line) 19 and the upper 2 bits are used for the address bus (address line) 20. Reference numeral 21 is a data control line (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 the data bus of the CPU2, and the second
It is connected to the data selector 8. The contents of ROM3 are RA
It may be data that creates the initial state in M1, or by the function of CPU2, which will be described later, determines the gamma curve for gamma conversion of the color image data input from the input data lines 14-17. Parameters corresponding to the respective input data lines 14 to 17).

Next, the operation will be described.

First, when the power is turned on, the CPU 2 initializes a peripheral device (not shown) according to a program by a normally used means. Next, the CPU 2 sets a set of parameters for gamma conversion of the image data input from the ROM 3 to the input data line 14 ay
And take out by. The CPU 2 controls the first data selector 6 to control the address bus 19 and the address line 1 and the data selector 7 to connect the address bus 20 and the address line 11, and connects the address bus 18 of the CPU 2 to the address input of the RAM 1. To do. Further, the CPU 2 controls the second data selector 8 to connect the data bus 22 to the data input of the RAM 1 via the data line 12. Next, the CPU 2 sets the address bus 20 and the address line 11 composed of the upper 2 bits of the 10-bit address bus 18 to "0" and sets the address line 19, that is, the address line 10.
While sequentially changing the address of "0 to 255", the gamma conversion data corresponding to the gamma curve calculated by the CPU2 by the method described later by the set of parameters ay and by is transmitted via the data bus 22, that is, the data line 12. Then, write to the lower 256 bytes of RAM1 by a commonly used method. Then, CPU2
Takes out a set of parameters am and bm for gamma converting the image data input from the ROM 3 to the input data line 15,
The address line 20 and the address line 11 are set to "1", and the gamma conversion data is written in the following 256 bytes of RAM1 as described above. Subsequently, the CPU 2 sets a parameter set ac for gamma conversion of the image data input from the ROM 3 to the input data line 16.
And bc are taken out, the address line 20 and the address line 11 are set to "2", and the gamma conversion data is written in the subsequent 256 bytes of the RAM1 as described above. Subsequently, the CPU 2 takes out a set of parameters ak and bk for gamma-converting the image data input from the ROM 3 to the input data line 17, sets the address line 20 and the address line 11 to “3”, and stores them in the RAM 1 as described above. Write the gamma conversion data in the following 256 bytes. Next, the CPU 2 switches the data selector 7 to connect the control line 21 to the control line 11 and switches the second data selector 8 to switch the data line 12
Is connected to the output data line 13. As a result, RAM1 becomes CPU2
Gamma conversion data of RAM1 determined by the image data signals Y, M, C, K input from the input data lines 14 to 17 and the identification signal input from the control line 21 to the output data line 13 Output. As described above, the identification signal acts on the first data selector 6 to select one of the input data lines 14 to 17 and becomes the upper address of the RAM 1 so that one written gamma conversion table (gamma conversion table) is selected. Select one of the data collections). Therefore, for example, the control line 21
If the identification signal input to is “1”, input data line 15
The image data signal M is connected to the data line 10, and the image data signal M “0 to 255” is substantially “256” on the data line 9.
.About.511 ", the data is converted by the gamma conversion table created second in the RAM 1 and sent to the output data line 13.

However, the gamma conversion does not always give desirable results for all signals on the input data lines 14-17. For example, 512 in RAM1 corresponding to image data signal C
If you want to rewrite the third gamma conversion table stored at addresses ~ 767, input a set of parameters ac ', bc' for making that curve from the input devices 4 and 5, and the CPU2
Controls the first data selector 6, the data selector 7, and the second data selector 8 to control the address bus 19 and the data line 10, the address bus 20 and the control line 11, and the data bus 22 and the data line 12, respectively. Connecting. Then, the address bus 20 is set to "2" and the address bus 19 is sequentially changed from 0 to 255, and the address data 512 to 767 are substantially input to the lower 8 bits of the data line 9 to the address input terminal of the RAM1 and input. Gamma conversion data 512 to 767 forming a gamma curve calculated by the CPU 2 from the parameters ac 'and bc' input from the devices 4 and 5 are sequentially written into the data input terminal of the RAM 1. When this writing is completed, the data selector 7 and the second data selector 8 connect the control lines 21 and 11 to the data line 12 and the output data line 13, respectively. RAM1 which is usually required
The chip enable end, the read / write end, the control line and the chip enable end of the ROM3, the address and the read line, and the address lines and interrupt lines of the input devices 4 and 5 are connected by a known technique. Not shown.

Next, the rewriting operation of the gamma conversion table will be described.

Arbitrary parameters ai (shown in FIG. 2) from the input devices 4 and 5,
When bi (shown in FIG. 3) is input, the following linear equation is first determined, and Y = ai (X−bi) (1) Then, the CPU 2 determines it by the above equation (1). Using the calculated Y, the gamma conversion data is d = 0 to 255 from the following formula (2).
Calculate up to. In addition, [] is a Gaussian symbol.

However, Yi = a (Xi−b) for b ≦ Xi ≦ (255 / a) + b Yi = 0 for Xi <b Yi = 255 for Xi> (255 / a) + b Yi = −ab for Xi <0 and b <0.

FIG. 4 shows an example in which the gamma conversion data 0 to 255 are calculated based on the equations (1) and (2) for the parameters of a = 2 and b = 63. However, in the second equation, n = 9
And

Similarly, FIGS. 5 to 6 are gamma curves calculated according to the above procedure, the solid line indicates Yi, and the broken line is Table (d).
, And the horizontal axis represents the table numbers (d) 0 to 255, and the vertical axis represents the gamma conversion value.

Next, a method of outputting the contents (Table (d)) of the gamma conversion table created in the RAM1 as the test mode will be described.

The CPU 2 controls the first data selector 6 and the data selector 7 to connect the address bus 18 to the address line 9 of the RAM 1 substantially. Subsequently, the CPU 2 controls the second data selector 8 to connect the data line 12 of the RAM 1 to the output data line 13. After that, the CPU2 uses 0 to 1023 on the address bus 18 by the usual means.
Output all address data of. At that time, the entire contents of RAM1 are sent to the output data line 13.

Next, the gamma conversion table creation and output preparation operation will be described with reference to the flowchart of FIG.
Note that S1 to S16 represent each step.

First, the CPU 2 controls the first data selector 6 to connect the address line 19 and the data line 10 (S1), and also controls the data selector 7 to connect the address bus 20 and the address line 11 (S2). ), Similarly controlling the second data selector 8 to connect the data bus 22 and the data line 12 (S
3). Then, the CPU 2 sends "0" to the address bus 20 (S4). Next, it is judged whether or not "4" is sent to the address bus 20 (S5), and if NO, the parameter set ay and by are fetched from the ROM 3 (S6), and the CPU 2 sends the address bus.
"0" is sent to 19 (S7). Then, it is determined whether the address value of the address bus 19 is "256" (S8), and NO
In case of, the CPU2 causes the gamma conversion data 0 to 25 as described above.
5 is calculated (S9), gamma conversion data 0 to 255 is sent to the data bus 22 (S10), and this gamma conversion data 0 to 255 is written from the data line 12 to the data input terminal of RAM1 (S1
1) Then, the address value of the address bus 19 is incremented by "1" and the process returns to step S8 (S12). On the other hand, if YES in the determination in step S8, the address value of the address bus 20 is incremented by "1" and the process returns to step S5 (S13).
On the other hand, if YES in the determination in step S5, the output preparation operation of the created gamma conversion data is started. First, the control of the first data selector 6 is transferred to the control line 21 (S14), and the CPU 2 switches the data selector 7. Control line 21 and address line 11 are connected (S15), and second data selector 8 is switched to connect data line 12 and output data line 13 (S1).
6), output preparation is completed.

Next, the operation of rewriting the gamma conversion table 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 (S21), and also controls the data selector 7 to connect the address bus 20 and the address line 11 (S22). ), Similarly controlling the second data selector 8 to connect the data bus 22 and the data line 12 (S23). Then, the parameter corresponding to the second parameter of the present invention for the CPU 2 to form a new gamma curve
Ac 'and bc' are fetched from the input devices 4 and 5 (S24), and then the address bus 20 is set in accordance with the identification signal corresponding to the first parameter of the present invention input from the control line 21, for example, "2". Set (S25) and send "0" to the address bus 19 (S26). Then, it is determined whether the address value of the address bus 19 is "256" (S27), and if NO, the CPU 2 sends the gamma conversion data "256" according to the parameters ac 'and bc' fetched in step S24. Calculate (S28), C
PU2 controls the second data selector 8 to connect the data bus 22 and the data line 12 (S29), and newly writes the gamma conversion data calculated in step S28 to the addresses 512 to 767 in RAM1 (S30). Then, the address value of the address bus 19 is incremented by "1" and the process returns to step S27 (S31). On the other hand, if YES in step S27, the write operation ends.

Next, the pseudo signal generating operation will be described with reference to the flowchart of FIG. Note that S41 to S47 represent each step.

First, the CPU 2 controls the first data selector 6 to connect the address bus 19 and the data line 10 (S41), and also controls the data selector 7 to control the address bus 20 and the control line 11.
Are connected (S42), and the second data selector 8 is also controlled to connect the data line 12 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), and then determines whether the address value of the address bus 18 is "1024" (S45). For example, the gamma conversion data "0 to 1024" stored in the RAM 1 are sequentially output to the output data line 13 via the data line 12 (S46). Then, the address value of the address bus 18 is incremented by "1" and the process returns to step S45 (S47). By repeating these steps S45 to S47, the pseudo signal (gamma conversion data) is output from the RAM1 as if the color image data were sent to the input data lines 14 to 17. On the other hand, if YES in the determination in step S45, the pseudo signal generating operation ends.

〔The invention's effect〕

As described above, according to the present invention, the creating means creates the gamma conversion data selected by the first parameter from the plurality of conversion data based on the second parameter for creating the conversion data, and writes it in the memory. Gamma conversion data corresponding to any type of image data created on the memory based on the type of each input image data,
By inputting the desired first and second parameters from the input device, the converted data with the desired characteristics can be rewritten,
It is possible to perform various image conversions on each of a plurality of types of input image data.

[Brief description of drawings]

FIG. 1 is a 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 calculated value of gamma conversion data. FIG. 5 shows an example, FIG. 5 and FIG. 6 are waveform diagrams showing gamma conversion data characteristics, and FIG. 7 is a flow chart for explaining a gamma conversion table creation and output preparation operation.
FIG. 8 is a flow chart for explaining the rewriting operation of the gamma conversion table, and FIG. 9 is a flow chart for explaining the pseudo signal generating operation. In the figure, 1 is RAM, 2 is CPU, 3 is ROM, 4 and 5 are input devices, 6
Is a first data selector, 7 is a data selector, and 8 is a second
Data selectors, 9, 10, 11 are address lines, 12 are data lines, 13 are output data lines, 14-17 are input data lines, 18, 19,
20 is an address bus, 21 is a control line, and 22 is a data bus.

Front page continuation (72) Inventor Naoto Kawamura 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (56) Reference JP-A-58-186291 (JP, A)

Claims (1)

[Claims] 1. A data input means for inputting a plurality of types of image data together with identification data indicating the type of image data, and a gamma conversion data for converting characteristics of the image data input by the data input means. Means and a plurality of gamma conversion data corresponding to a plurality of types of image data created by the creating means can be stored, and one of the plurality of gamma conversion data is selected and selected according to the input identification data. Memory for converting the input image data using the gamma-converted data and outputting the converted data, and a first parameter indicating which conversion data of the plurality of gamma-converted data is to be changed and gamma-converted data creation And a parameter input means for inputting a second parameter for The first of which
A gamma conversion circuit, characterized in that gamma conversion data selected by a parameter is created based on a second parameter for creating conversion data and written in the memory.