JPS635485A - Image data compression circuit - Google Patents

Abstract

PURPOSE:To improve the compressibility by dividing color image information represented as multivalued information at every primary color into monochromatic image information and color information and compressing them with a picture element unit. CONSTITUTION:The display areas of respective display colors are segmented in parallel in a subscanning direction. Color display information are stored in memories 41-43 at every RGB, read in parallel by a raster scanning and converted to monochromatic display information represented by one bit at every picture element in a OR circuit 1'. The output of the circuit 1' is selected 6, compressed 3 at every scanning line unit by the use of code P (n) indicating the selected memory and the number of the picture elements D (m) and filed together with attribute information except the type of the primary color. In a color information forming part 2, compression information is restored and at the time of writing in the memories 41-43, information is formed in a form capable of using the color information as a memory selection signal as it is. Namely, the color information is formed and filed by the start and the end of the scanning line by a code EOL and the completion of the information by a code RTC. According to such constitution, a compression processing time is shortened and the quantity of the information after the compression can be reduced.

Description

[Detailed Description of the Invention] [Summary] By configuring color image data expressed as multi-value data for each primary color in pixel units to be compressed separately into monochrome image data and color data, the compression ratio can be improved. I tried to improve it.

[Industrial application field]

The present invention relates to an image data compression circuit.

Image data consists of 9 images and figures as a structure of pixels.
This is expressed as bit data in pixel units.

Therefore, image data has a very large amount of data, but on the other hand, it is characterized by a relatively high degree of redundancy. For this reason, data compression is usually applied when files or transfers are made.

The aim is to reduce file capacity and improve transfer speed.

In particular, in the case of color image data, each pixel is generally represented by multivalued data for each of the three primary colors of blue, green, and red, so the amount of data is about three times that of monochrome data.

At this time, it is particularly desired to improve the pressure ER efficiency in color image data.

[Conventional technology]

Figure 4 is an explanatory diagram of the first conventional example, which is used when filing color display data written in the image memory (also called frame memory) in a color display device. .

As the image memory, red (R), green (G), blue (B)
It has three image memories, a first image memory 41, a second image memory 42, and a third image memory 43, for each of the three primary colors, and the color display data is converted into 3-bit data for each primary color in pixel units. Write as.

When compressing and filing this, the contents of each image memory 41 to 43 are read separately by rask scanning, and the compression processing unit 3' uses a one-dimensional encoding method that is internationally standardized for facsimile. M H (M
Data is compressed line by line (scanning line) using a modified Huffman (modified Huffman) method, a two-dimensional encoding method (MR (Modified Read)), etc.

It is stored in file 5 with attribute data such as primary color type, line length, and number of lines.

FIG. 5 is an explanatory diagram of the second conventional example, and in this case,
1st line data stored in the first image memory 41, 1th line data stored in the second image memory 42, 1st line data stored in the third image memory 43・Read the second line data stored in the first image memory 41 serially in order, and read the first line data of the first image memory 41 and the first line data of the second image memory 42. The data and the data of the first line of the third image memory 43 are connected in series to form one line, and the second and subsequent lines are similarly processed by the compression processing unit 3' using the same method as in the first conventional example. The data is compressed using , and attribute data is attached to each line and stored in file 5.

[Problem that the invention seeks to solve]

In the first conventional example, it is necessary to compress data for each primary color, so if this is done in one compression processing section, there is a problem that it will take approximately three times as much processing time as in the case of monochrome.

In the second conventional example, the amount of data to be compressed per line is three times that of monochrome, so there is a problem that data compression similarly requires approximately three times as much processing time.

Further, in both conventional examples, the amount of data after compression is nearly three times that of the monochrome case, so there are problems in that a large-capacity file device is required and it takes a long time to restore the data.

That is, two objects of the present invention are to reduce the processing time required for data compression and to reduce the amount of data after compression.

[Means for solving problems]

The image data compression circuit according to the present invention is as shown in the principle diagram of FIG.

and a data conversion unit 1 that converts color image data expressed as multi-value data for each primary color in units of pixels into monochrome image data.

and a color data generation unit 2 that generates color data representing color attributes of each pixel from the color image data.

The component includes a compression processing section 3 that compresses the converted monochrome image data and the generated color data for each scanning line.

[Effect]

Pattern information and color data expressed in the form of monochrome image data are extracted from color image data by a data converter 1 and a color data generator 2, respectively, and these are compressed separately.

The amount of data in the former is approximately one-third of multicolor image data, and the amount of data in the latter is used when there are only a few types of display colors, or when the display area is predetermined for each display color. In many cases, the amount of data can be significantly reduced, and the processing time and amount of data after compression can be reduced accordingly.

[Embodiment] Fig. 2 is a configuration diagram of the embodiment, in which, in addition to the symbols explained in the conventional example and the principle diagram, 1' is an OR circuit used as a data conversion section, and 6 is an output or an output of the OR circuit 1'. Selection circuit (MPX) that selects the output of the color data generation section 2
represents.

The functions and operations of each part will be described below in the case of compressing color display data displayed in a pattern as shown in FIG. 3(a).

In this example, one display color is three colors: red, edge, and blue.

This is a case where the display area on the display surface for each display color is divided parallel to the sub-scanning direction.

This color display data is divided into red, green, and blue colors.

For the first image memory 41, second image memory 42, and third image memory 43, respectively.

The information is stored as shown in FIG. 3 (bl to (d)).

The stored contents of each image memory 41 to 43 are read out in parallel by rask scanning under the control of a control section (not shown), and are read out in parallel for each pixel in an OR circuit 1'.
Converted to monochrome display data expressed in bits.

The output of the OR circuit 1' is given to the compression processing section 3 via the 2 selection circuit 6, and is processed by the MH method of the -dimensional encoding method.
The data is compressed line by line (scanning line) and stored in the file 5 as compressed pattern data along with other attribute data excluding the type of primary color.

In the color data generation section 2, when the compressed data is restored and written again to the original first image memory 41, second image memory 42, and third image memory 43, one color data is directly used as an image memory selection signal. In order to make it usable, color data is generated in the following form.

That is, in order to write the color image data as illustrated in FIG. is not written to either the second image memory 42 or the third image memory 43.

That is, there is no need to select an image memory for this one pixel. Therefore, in the sense of not selecting any image memory and in the sense of 1 pixel, (P
It is expressed as TO1+l]l)).

The second pixel, the first pixel, is “l” and is written into the first image memory 41. Also, from the 3rd pixel to the 8th pixel,
Since it is '0', there is no problem in selecting any image memory. In other words, there is no problem in writing to the same first image memory 41 as the second pixel.

Therefore, for the 7 pixels from the 2nd pixel to the 8th pixel, (P l+ +D (7
It is expressed as 1).

Similarly for the 9th and 10th pixels.

It is expressed as (P (4) + D (2)).

Note that P(0) does not select any image memory,
P(1) selects the first image memory 41.

P(2) selects the second image memory 42. P(
31 selects a first image memory 41 and a second image memory 42. P(4) selects the third image memory 43. P (51 is the first image memory 41
and the third image memory 43.

That is, for the data on the 7th line.

(P (ol + D l) + P (11 + D
It is expressed as (71+P'(4)+D(2)).

Similarly, color data as shown in FIG. 3(e) is applied to all lines (however, the EOL at the beginning of the first line represents the start code of the color data, the other EOLs represent the end code of the line, and the RTC (representing the end code of color data and the last line end code) can be generated.

Note that this can be represented by a planar figure corresponding to the display surface as shown in FIG. 3(f).

The color data generated by the color data generation section 2 is 1
A code P(nl (n = 0
．． 1, 2. ) and the number of pixels 1]ml (m=l.

2. , , ) by the run length of white pixels and the run length of black pixels, respectively.

Using the MH method, which is a -dimensional encoding method, data is compressed line by line and stored in file 5 as 9-color information compressed data.

In the above embodiment, when generating one color data, for example, the 3rd to 8th pixels of the 7th line are "O" (see Fig. 3 (al)), and it is difficult to decide which image memory to write to. Since there is no problem with this, it is written in the first image memory 41, which is the same as the second pixel.
This is very effective in increasing compression efficiency.

〔Effect of the invention〕

As explained above, the image data compression circuit according to the present invention is configured to compress color image data separately into monochrome image data and color data, thereby reducing the amount of data to be compressed. The processing time required for data compression 7 can be shortened, and the amount of data after compression can be reduced.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the principle of the present invention. FIG. 2 is a configuration diagram of the embodiment. FIG. 3 (al to ffl are explanatory diagrams of the embodiment. FIG. 4 is an explanatory diagram of the first conventional example. FIG. 5 is an explanatory diagram of a second conventional example. In the figure. 41 is the first image memory. 42 is a second image memory. 43 is the third image memory. Figure 1 Figure 2 (+11 Main scanning direction → Fig. 3 h　　　＼　　＼ Figure 4 h　　　h　　＼ Figure 5

Claims (1)

[Scope of Claims] A data conversion unit (1) that converts color image data expressed as multi-value data for each primary color in units of pixels into monochrome image data; A color data generation section (2) that generates color data; and a compression processing section (3) that compresses the converted monochrome image data and the generated color data for each scanning line.
).