JPH01279285A - Picture display - Google Patents

Abstract

PURPOSE:To reduce the quantity of data stored in a color designating information storing section and correlation table storing section by storing correlation tables indicating picture data corresponding to each color designating information belonging to each small area composed of plural picture elements in the correlation table storing section. CONSTITUTION:Small areas which respectively contain prescribed numbers of picture elements are set and the color of the part of an original picture corresponding to each small area is separated into color groups of prescribed kinds of colors. Then the color groups of one picture amount are stored in the color designating information storing section 2. Moreover, correlation tables indicating color designating information in corresponding to the picture data required for displaying each color of the color groups defined to each small area on a display section 4 are stored in the correlation table storing section 3 in advance. Since the color designating information is the information which distinguishes the color of the color group relevant to each small area, the quantity of the information can be made smaller when the number is limited to a small number. Thus the quantity of the information stored in the color designating section 2 can be reduced.

Description

[Detailed Description of the Invention] [Summary] An image display device having a display section that displays an image based on image data representing a color etc. corresponding to each pixel, which requires less storage capacity, and The purpose of the present invention is to provide an image display device that can display a significantly larger number of colors at the same time, and includes a readout control unit that sequentially instructs each pixel to be displayed to be read out, and a screen of the display unit. At least one color that divides a pixel into a plurality of predetermined small regions into small regions each consisting of a plurality of predetermined pixels, and specifies to which color each pixel belonging to the small region corresponds among a group of colors previously associated with each small region. A configuration including a color specification information storage section that stores color specification information for a screen, and a correspondence table storage section that stores, for each small area, a correspondence table representing image data corresponding to each color specification information belonging to the small area. It is.

(Industrial Application Field) The present invention relates to an image display device that performs color display, and more particularly to an image display device that has a display section that displays an image based on image data representing a color or the like corresponding to each pixel.

[Conventional technology]

Conventionally, in color gradation images, each pixel is R (Red),
G (Green), B (Blue)
It is expressed as tristimulus values, and currently, a length of 8 bits each for RGB is often used. This allows approximately 16 million colors to be displayed per -pixel.

However, if each pixel has 8 bits of RGB, the amount of data becomes large, so inexpensive color display devices require L
A method using UT (Look Up Table) is adopted.

There was an image display device that adopted this method as shown in FIG.

This device is an image display device having a display section 24 that displays an image based on image data representing the color etc. corresponding to each pixel, and as shown in FIG. 3, for each pixel on the screen, 1 for specifying the image data corresponding to the relevant pixel
It has a frame buffer memory 22 that stores color designation information for a screen, and a correspondence table storage section 23 that stores a LUT as a correspondence table representing image data corresponding to the color designation information.

Here, the image data is data representing each intensity for each RGB corresponding to each pixel, and based on the data, colors for displaying each corresponding pixel are displayed on the display unit 24 by additive color mixing. belongs to.

The display unit 24 is a DA converter 24r that converts data corresponding to each RGB from digital to analog and outputs a corresponding analog signal.

24g, 24b, and a color CRT 24c that sequentially displays corresponding pixels based on output analog signals.

In this example, by using the image data bits in the LUT, 256 colors out of 16 million colors can be displayed simultaneously.

That is, by using an 8-bit LUT for each color as in this device, the amount of data stored in the frame buffer memory 22 is smaller than when directly storing image data representing a color gradation image of 8 bits each for RGB. Thus, the amount of data is reduced to 1/3.

For example, in a device that uses an LUT when one screen has 512 x 512 pixels, the amount of data in the frame buffer memory 22 per screen is 262 kB, and the amount of data in the LUT is 768 B.

On the other hand, it has been known that since the correlation between images is large in local areas, there is little deterioration in image quality in terms of viewing angle even if the images are displayed using a small number of colors.

Traditionally, some image compression methods take advantage of this property.

In the block encoding method, for example, the IEICE is divided into small areas (blocks), each block is assigned two brightness levels, and each pixel is encoded by specifying which of the two brightness levels it belongs to. There was something to do.

This encoding method has the feature that encoding can be performed using a small number of bits without sacrificing gradation or definition.

Also, for color images, there is a coding method that expresses each block with two colors (IEEJ 1985 National Conference Proceedings No. 31 (1985) "Development of a two-color block coding method for color images") and In general, a coding method (IEICE technical research report IE86-65R multi-gradation block coding of color images) has been proposed that adaptively expresses images using one or more few colors.

However, when using the conventional block encoding method, as shown in FIG.
For each pixel belonging to the block, the image data representing the color corresponding to the block is converted into image data for each 8 bits of RGB for each pixel, and then stored in the frame buffer memory. 42, and a readout control section 41 reads out the image data corresponding to each pixel and directly displays it on the display section 44.

(Problems to be Solved by the Invention) By the way, in the conventional device shown in FIG.
The colors that can be simultaneously displayed on the screen of the display section 24 correspond to the capacity of the frame buffer memory 22 mentioned above, and due to the size of the capacity, the limit is 28 to 212 colors.

For this reason, the image quality varies depending on the image, and when the number of colors in the original image is large, the image quality deteriorates.

Furthermore, when trying to improve image quality, the problem is what colors should be registered in the LUT, and various methods are being studied. However, determining the representative color to be registered in the LUT involves dividing the RGB three-dimensional space using the colors that appear on one screen, which poses the problem of requiring a complex algorithm and a large amount of calculations. Was.

Furthermore, even in the apparatus shown in FIG. 4, since image data is directly stored in the frame buffer memory 42, the frame buffer memory 42
Not only does this require a memory with a large capacity, but if the capacity is limited, the image quality deteriorates.The present invention therefore aims to solve the above problems. The purpose of this project is to provide an image display device that requires less storage capacity and can display a significantly larger number of colors at the same time.

(Means for Solving the Problems) In order to solve the above technical problems, the present invention provides a display unit that displays an image based on image data representing a color etc. corresponding to each pixel, as shown in FIG. 4, the readout control section 1 sequentially instructs each pixel to be displayed to be read out, and a small area consisting of a predetermined plurality of pixels that constitutes the screen of the display section 4. Color specification information that stores at least one screen worth of color specification information that specifies to which color each pixel belonging to the small area corresponds, out of a group of colors previously associated with each small area. It has a storage section 2 and a correspondence table storage section 3 that stores, for each small area, a correspondence table representing image data corresponding to each color designation information belonging to the small area.

[Effect]

When displaying an image using this device, a small area containing a predetermined number of pixels on the screen is set in advance.

The reason for setting the small area here is that it can be assumed that the change in color within the range of the small area is generally small, so the number of colors used within the area is reduced to a small number. This is because it can be limited.

Therefore, the "predetermined number" is the number of pixels within a range where the change in color is small, and may vary depending on the image.

For each small region, the colors of the image corresponding to the part of the small region of the original image are decomposed into a color group consisting of a predetermined number (generally a small number) of colors, and the color is made to correspond to each color of the color group. At least one screen worth of color designation information for designating each color from a group is stored in a color designation information storage section 2.

Further, in the correspondence table storage section 3, a correspondence table representing the color designation information is stored in advance in correspondence with the image data necessary for displaying each color of the color group determined for each small area on the display section 4. Store it.

In this way, the image data necessary for displaying each pixel is not directly stored in the color specification information storage section 2, but only the color specification information necessary for specifying each color of the color group included in each small area is used. The correspondence between each color designation information and each image data is stored in the correspondence table storage section 3.

Therefore, since each color specification information is information that distinguishes which color (image data) of the color group belongs to each small area, if the number of colors belonging to the color group is limited to a small number (usually 2 1) A small amount of information is sufficient, and 1
Although the number of pixels included in the screen is enormous, and the amount of information of image data that displays the color corresponding to each pixel is also large, the amount of information stored in the color specification information storage section 2 is compared to the conventional method. It can be made smaller.

In order to display each pixel on the display section 4, the readout control section 1 sequentially issues a readout command to the color designation information storage section 2 and the correspondence table storage section 3.

The color designation information corresponding to the corresponding pixel stored in the color designation information storage section 2, which has received a reading command from the readout control section 1, is read out and sent to the correspondence table storage section 3.

At that time, among the image data corresponding to the color group of the small area to which the pixel that has been commanded to be read by the readout control unit 1 belongs, the image data designated by the color designation information is sent to the display unit 4 and the pixel is will be displayed.

〔Example〕

Next, embodiments according to the present invention will be described.

As shown in FIG. 2, this embodiment has a readout control section 11, a frame memory 12 as a color designation information storage section 2, a correspondence table storage section 13, and a display section 14.

The readout control section 11 has a line counter lla and a pixel number counter llb.

The line counter lla and the pixel number counter 11b are counters that generate addresses for specifying rows and columns for the frame memory 12 and the correspondence table storage section 13, respectively, from left to right or from top to bottom of the display screen. This indicates the pixel position during scanning in this order.

The frame memory 12 serving as the color specification information storage section 2 is configured to correspond to the screen of the display section 14 (512x512) w.
ord x 1 bit configuration, and for each block as a small area of 4 x 4 pixels, 1 bit of color designation information indicating which of the two representative colors is to be displayed for each pixel belonging to the block. is stored.

The correspondence table storage section 13 stores a predetermined digit part of the address specified by the line counter lla and the pixel number counter llb and 1 bit as the color designation information. L of
This is a memory 13b that stores UT.

In the LUT stored in the memory 13b, two-color gradation data as image data is written in an 8-bit format for each of RGB in the order of blocks appearing during scanning. The capacity of the memory 13b is (512/4X 512/4X
2) wordx 3Byte=32kwX 3Byte
=96kB.

Further, the display unit 14 includes a DA converter 14r that converts digital data corresponding to each RGB color as the read image data into a signal as analog data.
, 14g, 14b, and a color CRT 14c that displays a desired image based on the signal.

This embodiment operates as follows.

The pixel number counter Ilb and the line counter ll
If the contents of a are both 0, the color CRT 14c
Point to the pixel at the top left corner on the screen, and press both counters
When the contents of a and b are both expressed in hexadecimal notation (IFF
)X, the position of the lower right corner shall be displayed on the screen.

The pixel number counter llb counts up by 1 from 0, and when it reaches (IFF)X, it overflows, the contents are cleared, and the count-up operation is repeated again.

At the same time, the line counter lla starts from 0, and each time the pixel counter llb overflows, it receives a carry from the pixel counter llb and counts up by 1.

When both the line counter lla and the pixel number counter 11b reach (IFF)X, one scan for one screen from left to right and top to bottom is completed.

Now, as in this example, the pixel number counter llb is (OOE)
, the case where line counter Lla points to (009)x will be explained.

One bit is read out from the frame memory 12 as color designation information stored at each pixel position accessed by both counters 11a and 11b. The information for this 1 pit 1 is stored in the address register 13 of the correspondence table storage section 13.
It is held at the least significant bit (LSB) of a.

Next, line counter lla and pixel number counter llb
The upper seven bits of the address register 13a are held in the upper and middle positions of the address register 13a, respectively.

Therefore, the address register 13a specifies the color of the pixel position of the pixel number counter lla and line counter lla in the LUT, and this representative color is read out from the memory 13b of the corresponding table storage unit 13. .

The read representative colors are 8-bit data for each of RGB and are sent to the DA converters 14r, 14g, and 14 of the display section 14, respectively.
The image data is sent to the color CRT 14c as each image data, and a signal having a corresponding level is subjected to digital-to-analog conversion (DA conversion) and is sent to the color CRT 14c.

Note that although the above description concerns a specific pixel position, the same applies to other pixel positions.

As pixel positions are designated by the pixel number counter llb line counter 11a from left to right and from top to bottom, the representative colors on the LUT at the corresponding positions are read out and sequentially displayed.

Furthermore, although RGB signals are used in this embodiment, this can be expressed by two colors for each block using data from another color system such as YIQ, and then converted to RGB by calculation before DA conversion. After the DA conversion, the data may be converted to RGB using a matrix circuit.

Furthermore, although this embodiment shows an example in which each block is expressed in two colors, it is not limited to two colors if data from the above-mentioned document "Multi-gradation type block coding of color images" is used.
It is also possible to display in 4 colors, 8 colors, etc.

Furthermore, although this embodiment describes only color display, even in the case of monochrome gradation images, the three components of RGB are 1
The present invention can be applied in the same manner even if it is only a component.

Furthermore, the present invention may be applied by treating a color image as three monochrome images, assuming that there are three separate image data components.

〔Effect of the invention〕

As explained above, in the present invention, the amount of data to be stored in the color designation information storage section and the correspondence table storage section can be made relatively small. For example, in this embodiment, the amount of data is 4 bits/pixel, which is approximately 1/2, compared to 8 bits/pixel in the prior art.

However, the number of colors that can be displayed simultaneously can be significantly increased compared to the conventional example (for example, in this example, 512/4
x512/4 x2=215 colors). Therefore, better image quality can be obtained than in the conventional method, and the capacity required for each storage section is also smaller than in the conventional method.

Further, the representative color can be easily determined for each small area.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of the principle of the present invention, FIG. 2 is a diagram showing an image display device according to an embodiment, FIG. 3 is a diagram showing an image display device according to a conventional example, and FIG. 4 is a diagram showing another conventional image display device. FIG. 2 is a block diagram according to an example. 1.11... Readout control section 2.12... Color specification/1h information storage section 3.13... Correspondence table storage section 4.14... Display section゛] is Corridor 7'Q 'l' / '70 Figure 4

Claims (1)

[Claims] In an image display device having a display unit (4) that displays an image based on image data representing a color etc. corresponding to each pixel, sequential reading is performed for each pixel to be displayed. A readout control unit (1) that issues commands; and a readout control unit (1) that divides the pixels constituting the screen of the display unit (4) into small areas each consisting of a predetermined plurality of pixels, and divides the pixels of the display unit (4) into small areas each consisting of a predetermined plurality of pixels, and also divides the pixels of the display unit (4) into a plurality of predetermined small areas, and divides the pixels of the screen into a plurality of predetermined small areas, and divides the pixels of the screen of the display unit (4) into a plurality of predetermined small areas, and also divides the pixels of the screen of the display unit (4) into a plurality of predetermined small areas. Among them, a color specification information storage section (2) that stores color specification information for at least one screen specifying which color each pixel belonging to the small area corresponds to; A correspondence table storage unit (
3) An image display device comprising: