JP3038856B2 - Image data processing method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for processing image data, and more particularly to a method for processing image data by a bitmap method.

[Summary of the Invention]

The present invention relates to an image data processing method for dividing one screen into predetermined pixel units, setting a predetermined type of color data that can be used for each divided screen, and obtaining color data for each pixel. The color data of the pixel adjacent to the divided screen is set to the same code number as the color data of the pixel of the adjacent divided screen, and the code numbers of the color data are aligned when the image data is compressed. , So that it can be easily compressed.

[Conventional technology]

2. Description of the Related Art Conventionally, when various image data such as video signals are stored in a memory, for example, data such as color is added to each pixel constituting one screen to make digital data, and data of all pixels for one screen is stored in a memory. Was remembered.

[Problems to be solved by the invention]

However, it is better that the memory capacity for processing such image data is as small as possible, and it has been demanded that the amount of image data be compressed in some way and stored in the memory. In this case, various compression methods have been conventionally proposed, but in the conventional method, no consideration is given to compression at the stage of creating the original image data, and compression is performed depending on the state of the image. In some cases, the data amount of image data for one screen greatly differs. That is, for example, when there is a large change in color in one screen, the amount of information is generally larger than in a screen in which the change in color is small.

An object of the present invention is to enable image data to be satisfactorily compressed.

[Means for solving the problem]

The image data processing method of the present invention includes a plurality of palette data, each of which has a plurality of color data to which a code number is assigned for each color, and prepares a plurality of palette data each of which is a combination of different color data. Is divided into predetermined pixel units, the palette data usable for each divided screen is determined, and the color data of the palette data can be used for the pixels in the divided screen, and the color data used for each pixel is In the image data processing method indicated by the code number, when different pallet data is used in a predetermined divided screen and a divided screen adjacent to the divided screen,
Set the code number of pallet data used in the corresponding divided screen so that the code number of the color data of the pixel adjacent to the other divided screen is the same as the code number of the color data of the pixel of the adjacent partner. It is like that.

[Action]

By doing so, the code numbers of the color data are more likely to be aligned between the adjacent divided screens, and when compressing image data, the same code number is continuously processed in many cases. It is possible to increase the compression ratio even if different colors are used every time.

〔Example〕

Hereinafter, an embodiment of an image data processing method according to the present invention will be described with reference to the accompanying drawings.

In this example, a video signal of a still image is converted into bitmap image data using a pallet. First, bitmap image data using the pallet will be described. This bitmap image data divides the video signal of one still image into a plurality of sections. For example, as shown in FIG.
The video signal of one screen composed of 192 pixels in the vertical direction is
The image is divided into 64 × 8 pixel sections, and is divided into 768 sections of 32 sections in the horizontal direction × 24 sections in the vertical direction. in this case,
In the following description, each section is defined as one character.

Then, usable color data is set for each character, and in this example, palette data is provided as the color data. This pallet data is 8 for each still image.
Each type of palette data stores R, G, and B coloration data of 16 types of colors, and color numbers from 1 to 16 are assigned to these 16 types of colors. Has been granted.

For each of the 768 characters constituting one screen, data (hereinafter referred to as screen data) indicating which of the eight types of pallet data to use is set, and the screen data is used by each character. The pallet to be used is determined.

In the character data in which the pixel data of each character is stored, data of a color number (any number from 1 to 16) is set for each pixel, and a color number of a palette corresponding to each character is set. , The color of each pixel is determined.

By using bitmap image data using pallet data in this way, 16 colors × 8 pallets = 128 colors for the entire screen, and 128 colors can be used at the maximum. In each pixel unit, only the color numbers from 1 to 16 need to be assigned, and the data amount of the entire screen can be greatly reduced.

Here, FIG. 1 shows a configuration for displaying bitmap image data using the pallet data. In FIG. 1, (1) indicates a central control unit (CPU) for controlling image display. The CD is controlled by the central control unit (1).
One predetermined image data is read out from a disk (CD ROM) mounted on the ROM device (2), and read out from the RAM (3),
(4) and (5) are temporarily stored. In this case, RAM
(3) Store 8 types of pallet data in RAM
Screen data indicating a pallet corresponding to each character is stored in (4), and character data indicating color number data for each pixel in each character is stored in the RAM (5).

FIG. 3 and FIG. 4 are diagrams showing the storage state of the pallet data in the RAM (3), and this pallet data is stored.
The RAM (3) is called a color bank. As shown in FIG. 3, data of 16 colors of each pallet from the first pallet to the eighth pallet are stored in individual areas. As the 16-color data of each palette, as shown in FIG. 4, 16-color numbers are set by 4-bit data, and R (red), G (green), B (blue) level data is set with 5 bits.

FIG. 5 is a diagram showing the storage state of the screen data in the RAM (4), in which the character code assigned to each of the 768 characters is indicated by 10 bits, and the pallet number corresponding to each character code Can be set with 3 bits.

FIG. 6 is a diagram showing a storage state of character data in the RAM (5). FIG. 6 shows a storage area for one character, and one storage area is provided for each character. The dot number assigned to each 64 pixels is indicated by 6 bits, and 4
Bit color numbers can be set. In this case, the order in which dot numbers are assigned to 64 pixels in one character is, for example, as shown in FIG.
The second and third pixels are assigned to each pixel following the horizontal line.
Are sequentially assigned to the lower line in the same manner, and the pixel at the lower right corner is finally number 64. Therefore,
For example, as shown in FIG. 7, a predetermined character A and a character B adjacent to each other on the left and right include a pixel having a dot number of 8, 16, 24, 32, 40, 48, 56, 64 of the character A and a pixel of the character B. Pixels with dot numbers 1, 9, 17, 25, 33, 41, 49, and 57 are adjacent to each other.

Then, under the control of the central control unit (1), the color number data is read out from the RAM (5) one pixel at a time to the image display unit (6), and the color number data is read out based on the screen data stored in the RAM (4). Pallet data in RAM (3)
, And coloring of each pixel is performed. And
When the image display unit (6) performs the coloring process for all the pixels for one screen, a horizontal synchronization signal, a vertical synchronization signal, and the like are added to the data for one screen to obtain a predetermined video signal. The signal is supplied to the monitor receiver (7) and displayed on the screen of the monitor receiver (7).

In this example, when creating bitmap image data using a pallet for displaying and the like in this manner, the color data of the pixels at the left corner and the right corner in each character is converted to another adjacent pixel. The same code number (color number) is used as the color data of the pixel of the character as much as possible. For example, as shown in FIG. 7, a predetermined character A and a character B adjacent to each other on the left and right include a pixel having a dot number 8, 16, 24, 32, 40, 48, 56, 64 of the character A and a character B Pixel numbers 1, 9, 17, 25, 33, 41, 49, 57
Image data is created so that each has the same color number as much as possible. In this case, when adjacent pixels of the character A and the character B have the same color, the character A
If the same palette is used for the character and the character B, the same color number is obtained as it is. If the adjacent pixels of the character A and the character B have different colors, the character A and the character B use different numbers of palettes, and the color numbers used by the adjacent pixels are the same. Create each palette to become.

For example, when the pixel with the dot number 8 of the character A is white and the pixel with the dot number 1 of the character B is black, the color number 1 of the first palette is white and the color number 1 of the second palette is white. Is black. Then, the screen data is set so that the character A uses the first palette and the character B uses the second palette.

By doing so, the pixel of dot number 8 of the adjacent character A and the pixel of dot number 1 of the character B have the same color number, and the character data of the adjacent pixel becomes the same.

In this way, by making the color numbers of the pixels of the right and left adjacent characters the same as much as possible, the compression ratio becomes large when the bitmap image data is run-length compressed. In other words, the run-length compression will be described. For example, as shown by an arrow a in FIG. 7, pixels constituting each horizontal line are sequentially scanned to count the number of consecutive pieces of the same pixel data. When data is continuous, run-length-compressed data is added to the continuous number, and the amount of data is compressed by omitting the continuation of the same pixel data. In general, this run-length compression can greatly compress the data such as color in a single image when the change is small, but the compression amount is too large when the data such as color changes largely. There is a drawback that must not be.

On the other hand, when the bit-mapped image data of the present example is compressed by the run-length compression, the pixel data of the adjacent characters is often the same even when there is a large change in color in one image. When the pixels constituting each horizontal line are sequentially scanned, even if the character changes and the color changes, it is possible to compress the same data as the same data, and the image is based on an image with little color change. A large compression ratio can be achieved, and the data amount can be reduced.

The run-length compression is performed by, for example, the image display unit (6), and is mainly transmitted from the image display unit (6) via a predetermined transmission path or recorded (stored) in a predetermined recording medium or memory. This is done to reduce the amount of data.

In the above-described embodiment, the case where the scan is performed in the horizontal direction to perform the run-length compression has been described. However, when the scan is performed in the vertical direction and the run-length compression is performed, the pixels vertically adjacent to each character are identical. Color number.

〔The invention's effect〕

According to the present invention, the code numbers of color data are often aligned between adjacent divided screens, and when compressing image data, the same code number is frequently processed continuously. Even if the colors used are different, it is possible to increase the compression ratio when performing run-length compression.

[Brief description of the drawings]

FIG. 1 is a system configuration diagram for applying one embodiment of the present invention, and FIGS. 2, 3, 4, 5, 6, and 7 are image processing according to one embodiment. It is an approximate line figure used for explanation. (1) Central control unit, (2) CD ROM unit, (3),
(4) and (5) are RAM, (6) is an image display unit,
(7) is a monitor receiver.

Claims (1)

(57) [Claims] 1. A plurality of color data sets each having a code number assigned to each color, a plurality of palette data sets each of which is a combination of different color data are prepared, and one screen is set in a predetermined pixel unit. The palette data that can be used for each divided screen is determined, and the color data of the palette data can be used for pixels in the divided screen,
In the image data processing method in which the color data used for each pixel is indicated by the code number, when different palette data is used in a predetermined divided screen and a divided screen adjacent to the divided screen, Set the code numbers of the pallet data used in the corresponding divided screen so that the code numbers of the color data of the pixels adjacent to the divided screen are the same as the code numbers of the color data of the adjacent pixels. Image data processing method.