JPH03168797A - Gradation converting circuit - Google Patents

Abstract

PURPOSE:To obtain a sufficient contrast by providing plural gradation register blocks stored with gradation blocks corresponding to plural gradation conversion characteristics corresponding to color data and control signal input terminals for inputting control signals for selecting one of the gradation register blocks. CONSTITUTION:The gradation register blocks 13A - 13E consist of 64 gradation registers stored with gradation data D'Y corresponding to gradation conversion characteristics and, for example, the gradation register block 13A is stored with specific values in respective gradation registers. Further, the respective registers of other gradation register blocks 13B - 13E are stored with values found from respective gradation conversion characteristics B - E previously. Further, conversion control signals SCA - SCE for selecting one of the five gradation register blocks 13A - 13E are inputted to the input terminals 14A - 14E. Consequently, the sufficient contrast is obtained regardless of a color to be displayed and the kind of a panel display.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a gradation conversion circuit used when displaying image data on a panel display.

``Prior Art'' FIG. 14 is a block diagram showing an example of the configuration of a graphics section of a 7<-sonal computer to which a conventional gradation conversion circuit is applied.
PU (central processing unit), 2 is video memory (VRAM) in which image data consisting of color codes is stored, 3 is C
The RT display 4 is a black and white panel display such as a plasma display, a crystal panel, or an EL display.

A display controller 5 generates a display address for VrtAM2 and generates a line clock and a frame clock to be supplied to the CRT display 3 or panel display 4.

Furthermore, 8-bit image data supplied from the display controller 5 is input to R (red), G (green), . B (blue) each 6
This is a color register table for converting into bit color data, and FIG. 15 shows an example of the configuration of the color register table 6. Color register table 6 has 256 color registers. This color register has an 18-bit structure, and each color data of R, G, and H is stored in 6 bits each.

In addition, in FIG. 14, 7 is a gradation conversion circuit,
R, G, supplied from the color register table 6
Each color data (256 colors) of H is divided into 16 gradations or 32
Convert to gradation data.

The gradation conversion displayed on the panel display 4 is R.
, G, H as color data Da, Da
, DB, and the gradation data to be converted is data Dy. Generally, this is performed based on the following equation.

Dy=0.3DR+0.5 9Da+0.1 1De・
・■ In such a configuration, when displaying image data on the CRT display 3, the display controller 5
Image data consisting of color codes is sequentially read from the VRAM 2 in synchronization with the display on the RT display 3. One of the 256 color registers in the color register table 6 is designated by the value of this color code, and the color data stored in the designated color register is supplied to the CRT display 3. As a result, the CRT display 3 displays a color corresponding to the above-mentioned color data.

Note that the color register has a 18-bit configuration, so 2
6 2, 1 4 4 (2") colors can be expressed. Also, since the color register table 6 is composed of 256 color registers, the CRT display 3 can display 262,144 colors. It is possible to display 256 colors.

On the other hand, when displaying image data on the panel display 4, the display controller 5 sequentially reads image data consisting of color codes from the VRAM 2 in synchronization with the display on the panel display 4. One of the 256 color registers in the color register table 6 is designated by the value of this color code, and the color data stored in the designated color register is supplied to the gradation conversion circuit 7. This gradation conversion circuit 7 converts color data into 16 gradation or 32 gradation data. This data is then supplied to the panel display 4, and the panel display 4 performs black and white display based on this data.

Note that the gradation DY shown by the formula (2) is expressed by 6 bits from 0 to 63. For example, in the case of ■6-gradation display, 16 gradations are assigned by the value of the upper 4 bits. Similarly, in the case of 32-gradation display, 32 gradations are assigned using the value of the upper 5 bits.

``Problems to be Solved by the Invention'' By the way, in the graphic section of the conventional personal computer described above, when displaying image data on the panel display 4, the limit is 16 gradations or 32 gradations. The disadvantage was that depending on the color, sufficient contrast could not be obtained.

Further, since plasma displays, liquid crystal panels, and EL displays each have different characteristics such as contrast, there is a drawback that depending on the type of panel display 4, sufficient contrast cannot be obtained.

The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to provide a gradation conversion circuit that can obtain sufficient contrast regardless of the color to be displayed or the type of panel display.

"Means for Solving the Problem" The present invention provides a gradation conversion circuit that converts color data supplied from a color register table into gradation data for a panel display, which performs a plurality of gradation conversions corresponding to the color data. A plurality of gradation register blocks each including a plurality of gradation registers storing gradation data according to characteristics, and a second one of the plurality of gradation register blocks, ! and a control signal input terminal into which a control signal for selecting the selected item is input.

"Operation" According to the present invention, when displaying image data on a panel display, for example, a gradation register block is selected according to the gradation conversion characteristic to which a control signal is input from the control signal input terminal. Then, when color data is supplied from the color register table, this gradation conversion circuit
Since a certain tone register block has already been selected, one tone register corresponding to color data is selected in this tone register block. Then, the selected gradation register outputs gradation data.

As a result, the gradation data is supplied to the panel display, and the panel display displays a predetermined gradation based on the gradation data to create a screen.

"Embodiment" First, before describing an embodiment of the present invention, a basic idea for solving the above-mentioned problem will be explained.

In the color register table 6 shown in FIG.
For example, R color data is 6 bits, so it takes values from 0 to 63, and is usually stored so that as the value increases, the red color becomes brighter. In other words, gradation is applied to the red color.

Furthermore, the gradation characteristics of the panel display 4 include linear and nonlinear gradation characteristics. Furthermore, depending on the color, contrast may be better achieved by non-linearly converting the gradation characteristics than by linearly converting the gradation characteristics.

Therefore, in the present invention, five types of gradation conversion characteristics shown in FIGS. 2 to 6 are prepared. Among these, the characteristics shown in Figure 2 are:
This is a linear conversion characteristic used in conventional technology.

That is, in the gradation conversion circuit, the R. The gradations obtained from the 6-bit values (0 to 63) of each color data of G and H are shown in Figure 2~
It is converted into a gradation having the characteristics shown in FIG. As a result, compared to the past, it is possible to provide contrast regardless of the displayed color or the type of panel display.

In fact, Figures 7 to ■! The characteristics of 16-gradation conversion shown in the figure are used approximately. In FIGS. 7 to 11, the characteristics A-E are the curves a''=e in FIGS. 2 to 6, respectively.
It corresponds to

This allows five types of 16-gradation conversion.

Here, these gradation conversion characteristics will be explained in more detail using the characteristics shown in FIGS. 2 and 7 as examples.

Since 6 bits, that is, values from 0 to 63, are converted into 16 gradations, it is sufficient to sequentially allocate four gradations to one gradation according to the following equation.

An example is shown in FIG.

64÷16=4···■ Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing the structure of a tone conversion circuit 7 according to an embodiment of the present invention.

Note that the other circuits of the graphic circuit of the personal computer have the same configuration as shown in FIG. In Figure 1, 9
~tl. are R, G, H color data DR, DC, respectively supplied from the color register table 6. DB
The input terminal 12 is a color/gradation conversion circuit that converts the input color data D*, Da, Do into 6-bit gradation data Dy based on the equation (2).

The lock consists of 64 gradation registers in which gradation data D'a corresponding to the gradation conversion characteristics shown in FIGS. 7 to 2 are stored. The values shown in FIG. 12 are stored in advance in each gradation register. In addition, other gradation register blocks 13. -13
．． The values obtained from the respective gradation conversion characteristics BE shown in FIGS. 8 to 11 are also stored in advance in each gradation register.

Further, 14A-146 are control signal input terminals to which a conversion control signal SCA-SCTR for selecting one of the five tone register blocks 13A-13H is input, and 15 is converted tone data. D' is a gradation data output terminal.

In such a structure, when displaying image data on the panel display 4, for example, the conversion control signal SCA is inputted from the input terminal 14A to select the gradation register block 13A among the five types of gradation register blocks ISA-13H.
In other words, the tone conversion characteristic A shown in FIG. 7 is selected. Then, when the display is synchronized and the image data consisting of the color code is sequentially read from the VRAM 2, the 25
Any one of the six color registers is specified, and the color data D n stored in the specified color register
, D c, and D B are supplied to the gradation conversion circuit 7.

As a result, in the color/gradation conversion circuit I2, the input color data DR. D c and D s are converted into 6-bit gradation data Dy based on equation (2). Furthermore, in this gradation conversion circuit 7, the gradation register block 13A has already been selected, so one gradation register corresponding to the gradation data Dy is selected in this gradation register block 13A. Then, from the selected gradation register, 4-bit gradation data D'y is outputted from the gradation data output terminal l5.

As a result, the gradation data D'A is changed to the panel display 4.
On the panel display 4, a predetermined gradation display is performed based on the gradation data D'y, and a screen is created.

In the embodiments described above, 16-gradation display has been described, but 32-gradation display can also be realized using the same concept.

Further, by applying the above-mentioned concept, it is possible to convert the gradation using gradation conversion characteristics other than those shown in FIGS. 2 to 6. For example, when inverting black and white, the gradation conversion characteristics shown in FIG. 13 may be used.

In this way, just by changing the value of the tone register,
Characteristics different from the gradation conversion characteristics prepared in advance can be easily realized.

"Effects of the Invention" As explained above, according to the present invention, there is an effect that sufficient contrast can be obtained regardless of the displayed color or the type of panel display.

Furthermore, if the contrast is not sufficient after executing the application program, the user can select another tone conversion characteristic by inputting a control signal.

Furthermore, the gradation conversion characteristics can also be selected in accordance with the characteristics of the panel display used.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of a gradation conversion circuit 7 according to an embodiment of the present invention, FIGS. 2 to 6 are diagrams each showing an example of gradation conversion characteristics, and FIGS. 16
12 is a diagram showing an example of the configuration of the gradation register block 13A, FIG. 13 is a diagram showing an example of the gradation conversion characteristic of black and white inversion, and FIG. 14 is a diagram showing an example of the gradation conversion characteristic of the conventional FIG. 15 is a block diagram showing an example of the configuration of a graphics section of a personal computer to which a gradation conversion circuit is applied. FIG. 15 is a diagram showing an example of the configuration of the color register table 6. 13A-131...Gradation register block, 14
A~l41...Control signal input terminal.

Claims (1)

[Scope of claims] In a gradation conversion circuit that converts color data supplied from a color register table into gradation data for a panel display, gradation data according to a plurality of gradation conversion characteristics corresponding to the color data. and a control signal input terminal to which a control signal for selecting one of the plurality of grayscale register blocks is input. A gradation conversion circuit characterized by: