JPH08294142A - Image information compression method and image display device using this method - Google Patents

Abstract

PURPOSE: To obtain the compression effect equal to or over that of the IPEG method or the like without using discrete cosine transformation in the compression method of image information. CONSTITUTION: Image information expressed in RGB is converted into YIQ expression (100) and only color information (I.Q) is averaged for each square area of 4-pixel (200) and the averaged color information (I, Q) is stored as 4-pixel data (300). Then differential run length compression is applied to each of the luminance information (Y) and the color information (I.Q) after compression, that is, a difference between adjacent data is obtained and only data of the difference 0 are subject to run length coding (400), and Huffman compression is applied succeedingly (500), and then the compression processing is finished. When the image information is expanded and displayed, the processing reverse to the processing above is executed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image information compression method for compressing image information, and an image display device for compressing and storing image information and reading the image information to display an image on a display.

[0002]

2. Description of the Related Art At present, various methods of compressing image information are known, but there is no deterioration of the image and
As a method with extremely high compression efficiency, for example, compression methods such as JPEG (Joint Photographic Experts Group) and MPEG (Motion Picture Experts Group) that are standardized by ITU (formerly CCITT; International Telegraph and Telephone Consultative Committee) are typical. Is widely known.

[0003]

However, the above-mentioned JPEG
In the image information compression method by MPEG or MPEG, a so-called discrete cosine transform (DCT) is used in the compression process. Therefore, when this is realized by hardware or software, the hardware configuration or the volume of software is There is a problem that the system becomes large in scale and the cost of the system becomes high.

In addition, when the discrete cosine transform (DCT) is used for an image with a drastic change and a clear boundary of an object to be drawn, for example, an image in which a large number of black characters are drawn on a white background, There is also a problem that the image is distorted at the boundary of the object and a high data compression rate cannot be expected.

The present invention has been made by paying attention to such a problem, and the IPE can be performed without using the discrete cosine transform.
An object of the present invention is to provide an image information compression method capable of obtaining a compression effect equal to or higher than that of G and the like, and an image display device using this method.

[0006]

In order to achieve the above object, according to the invention of claim 1, in the image information compression method for compressing color image information, the color image information is separated and converted into luminance information and color information. And compressing only the separated and converted color information.

According to the second aspect of the invention, in the image information compression method for compressing the image information consisting of the image information sequence, the difference between adjacent image information in the image information sequence is calculated, and there is a difference. In the case where the difference is the difference information indicating the difference, when there is no difference, the run information indicating that there is no difference and the length information indicating the number of consecutive times without difference are used to compress the image information sequence. Characterize.

According to the third aspect of the invention, in the image information compression method for compressing color image information, the color image information is separated and converted into luminance information and color information, and the separated and converted color information is obtained. Only the difference between the adjacent image information is calculated for each image information sequence of the separated and converted luminance information and each image information of the compressed color information, and if there is a difference, the difference is calculated. While outputting the difference information indicating that there is no difference, it is compressed into run information indicating that there is no difference and length information indicating the number of consecutive times without difference, and further Huffman compression is performed for each compressed image information sequence. It is characterized by:

According to the invention described in claim 4,
Alternatively, in the image information compressing method according to claim 3, the color image information is arranged in a matrix based on the position of the color image, and the compression of the color information is performed by adjoining x of the image information arranged in the matrix. It is characterized in that an average is taken for each of a plurality of color information for each predetermined size in the direction or the y direction, or for each matrix of a predetermined size, and the average value is used as the value of each color information.

Further, in the invention according to claim 5, in the image display device for compressing and storing the color image information and reading the compressed image information to display the color image on the display, the color image information is displayed. Image information converting means for separating and converting luminance information and color information, color information compressing means for compressing only the color information separated and converted by the image method converting means, and separated and converted by the image information converting means. Image information storing means for storing the luminance information and the color information compressed by the color information compressing means, and the luminance information and the color information of each pixel to be displayed on the display are read out from the image information storing means to obtain the color. Display control means for converting the image information to display a color image on the display.

Further, in the invention according to claim 6, in the image display device for compressing and storing the image information consisting of the image information sequence and reading the compressed image information to display the image on the display. The difference between adjacent image information in the image information sequence is calculated, and if there is a difference, it is used as difference information, and if there is no difference, run information indicating that there is no difference and continuous without difference With the length information indicating the number of times, a differential run-length compression means for compressing the image information sequence, and a Huffman tree is created based on the image information sequence compressed by the differential run-length compression means, and the Huffman The Huffman compression means for Huffman compression of the image information sequence according to the tree and the image information sequence compressed by the Huffman compression means are described. And image data sequence storage means for the image data sequence stored in the image information sequence storage means is read,
Huffman decompression means for decompressing the image information sequence before Huffman compression according to the Huffman tree, and the image information sequence decompressed by the Huffman decompression means, and the image information before the process by the process reverse to that of the differential run-legging means. A differential run-length expansion unit for expanding the sequence, and a display control unit for reading out each image information forming the image information sequence expanded by the differential run-length expansion unit and displaying an image on a display. It is characterized by

According to the invention of claim 7, in the image display device for compressing and storing the color image information and reading the compressed image information to display the color image on the display, the color image information is stored. Image information converting means for separating and converting luminance information and color information, color information compressing means for compressing only the color information separated and converted by the image method converting means, and separated and converted by the color information compressing means. For each image information sequence of the luminance information and each image information of the compressed color information, the difference between adjacent image information in each image information sequence is calculated, and if there is a difference, difference information indicating the difference When there is no difference, the run information indicating that there is no difference and the length information indicating the number of consecutive times without difference are used as the difference run length conversion for compressing each image information sequence. Huffman compression for compressing the image information sequence according to the Huffman tree while creating a Huffman tree for each image information sequence compressed by the reducing unit and the differential run length compression unit. Means, image information sequence storage means for storing each image information sequence compressed by the Huffman compression means, and each image information sequence stored in the image information sequence storage means is read out and Huffman compression is performed according to the Huffman tree. Huffman decompression means for decompressing each preceding image information sequence, and each image information sequence decompressed by the Huffman decompression means are decompressed to each image information sequence before the processing by a process reverse to that of the differential run-legging compression means. Differential run-length expansion means and each image information sequence expanded by the differential run-length expansion means Each image information of luminance information and hue information constituting converted into color image information, characterized by comprising a display control means for displaying a color image on a display.

According to the invention described in claim 8,
Alternatively, in the image display device according to claim 7, the color image information is arranged in a matrix based on the position of the color image, and the compression of the color information is performed in the adjacent x direction of the image information arranged in the matrix. Alternatively, it is characterized in that an average is taken for a plurality of color information for each predetermined size in the y direction or for each matrix of a predetermined size, and the average value is used as the value of each color information.

[0014]

According to the present invention, when the color image information is compressed, the color image information is separated and converted into the luminance information and the color information, and only the separated and converted color information is compressed.

Further, when compressing image information consisting of an image information sequence such as color image information, the difference between adjacent image information in the image information sequence is calculated, and if there is a difference, the difference is calculated. The image information is compressed into run information indicating that there is no difference when there is no difference and length information indicating the number of consecutive times without difference.
Further, after this differential run length compression, Huffman compression is further performed in order to improve the compression efficiency.

When decompressing and displaying the image information compressed in three stages as described above, first, the Huffman decompression process, which is the reverse process of the Huffman compression, is performed, and then the differential run length compression is performed. The reverse run length expansion process, which is the reverse process, is performed, and the luminance information and the color information that is compressed and not restored are converted into color image information and displayed based on this color image information.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an image compression method according to the present invention and an image display device using this method will be described below with reference to the drawings.

FIG. 1 shows the configuration of an embodiment of an image display device using the image compression method according to the present invention.

This image display device is provided as a display device for a display unit of a game board of a pachinko machine, and comprises a display module 1, an LCD display section 2 and a table control section 3.

The display module 1 includes a CPU 11 for giving a logical command relating to image display, a program ROM 12 in which an operation program of the CPU 11 is stored, and a character ROM 13 in which image information compressed in three stages as described later is stored. And V composed of two DRAMs or the like for storing display data obtained by expanding the compressed image information.
The compressed image data is read from the RAM 14 and the character ROM 13 based on a command from the CPU 11, the data is reproduced in the VRAM 14 and temporarily stored, and the data in the VRAM 14 is read at an appropriate timing to be displayed on the LCD display unit 2. It has a display controller 15 for displaying and processing a display image.

The LCD display section 2 is an STN or TFT.
System LCD, NT sent from the display module 1
The image is displayed based on the SC signal or the RGB signal.

The platform controller 3 is a circuit that generates so-called hit information for the pachinko machine and controls the hitting operation of various operating devices (not shown) in the pachinko machine. And a display control signal based on the hit operation control signal is sent via the parallel I / F to the CPU 11 of the display module 11.
To be sent to.

FIG. 2 shows a detailed internal structure of the display controller 15.

The display controller 15 includes a CPU interface 15a and a Huffman table.
RAM 15b, Huffman decompression circuit 15c, differential run length decompression circuit 15d, hardware drawing circuit 15e consisting of BitBit (enlargement / reduction rotation circuit) and straight line drawing circuit, DRAM controller 15f, cache memory (Cache) 15g, It is composed of a YUV (YIQ) -RGB conversion circuit 15h, a command processing sequencer 15i having a register, an LCDC register 15j, an image processing circuit 15k, an LCD controller 15m and the like.

Next, a method of compressing the image information according to the present invention stored in the character ROM 13 of the image display device configured as described above will be described.

FIG. 3 shows an outline of the image information compression method according to the present invention.

First, full-color image data represented by 8 bits of RGB on a computer device is separated and converted into YIQ representation, that is, luminance information (Y) and hue component (U).
And color information (U · V) composed of the color component (V) and converted into 5-bit information (step 100).

Next, in the state where only the color information (I · Q) is arranged in a matrix state, it is in four directions, that is, x,
An average is taken for each four-pixel square area adjacent in the y direction (step 200), and the averaged color information (I.
Q) is stored as the data of the four pixels (step 300). In the present embodiment, the description will be made by averaging four pixels adjacent to each other in the x and y directions. However, in the present invention, each of the color information arranged in a matrix state is adjacent to either the x direction or the y direction. Alternatively, an average may be taken for each arbitrary size or for a matrix of a size other than 4 pixels, and the average value may be used as the averaged value of each color information.

Therefore, the amount of color information (I · Q) is 1/4 each, and the amount of luminance information (Y) and color information (I · Q) before the separation conversion of this color information is respectively reduced. If it is 1, it is 3 as a whole, and it is 1 + 1/4 after separation and conversion of color information
+ 1/4 = 1.5, which means that the total amount of information is compressed to 1/2 of that before the separation conversion.

Then, each of the luminance information (Y) and the color information after the separation conversion is compressed by the differential run length coding method described later (step 400), and then compressed by the Huffman coding (step 500). , The compression process ends.

4A to 4D respectively show YIQ (YU) from the RGB image data of step 200 shown in FIG.
V) Shows the state of the image data when the image data is converted and compressed.

First, (a) shows image data Rmn, Gmn, of each RGB color represented by 8 bits of RGB.
Bmn (where m and n are natural numbers) is arranged in a matrix for each R, G, and B plane based on the position of each color image.

Then, the image data represented by each color of RGB is converted into luminance information (Y) and hue / color information (I / Q) which is two components of color information.

(B) shows a state in which each color image data of RGB is converted into luminance information (Y) and hue / color information (I / Q).

This conversion is performed by the matrix of 3 rows and 3 columns shown below. It should be noted that this matrix is a matrix expressing the NTSC signal, and the NTSC signal is generally Y
Since it is called IQ, the luminance information (Y) and the hue / color information (U / V) Y, U, and V are called Y, I, and Q, respectively. Y = 0.30 x R + 0.59 x G + 0.11 x B (0 ≤ Y ≤ 255) I = 0.60 x R-0.28 x G -0.32 x B (-153 ≤ I ≤ 153) Q = 0.21 x R -0.52 x G + 0 .31 x B (-132.6 ≤ Q ≤ 132.
6) When the I and Q components are 127 or more and -128 or less, the data are treated as 127 and -128, respectively.

Next, band compression of the color information is performed from the state shown in (b).

(C) shows a state in which the color information is band-compressed in each plane.

That is, the hue / color information (I / Q), which is two components of the color information, takes the average value of the values of 4 pixels adjacent to each other on two sides, and stores the average value as a representative value of 4 pixels and displays it. In doing so, the representative value is used as a value of 4 pixels. For example, in the case of color information "Q11, Q21, Q12, Q22" of 4 pixels in which two pieces of the Q plane are adjacent, the 4 pixe
The average value of l is set to Q1, and the average value Q1 is set to 4pixe.
It is stored as a representative value of l. By this operation, the I and Q components of the color information are reduced to 1/4.

Finally, the state shown in (c) is converted into discrete data.

(D) shows a state in which the luminance information (Y) and the hue / color information (I / Q) after compression are converted into discrete values.

That is, the data of each YIQ component is simply right-shifted by 3 bits so that the lower 3 bits of each data are discarded to form a discrete value of 5 bits.

The image information of the luminance information (Y) and the color information (I / Q) thus compressed is subjected to decompression processing such as differential run length decompression and Huffman decompression, which will be described later. It will be stored as display image data in the VRAM 14 shown in FIG.

Next, the compression processing by differential run-length coding in step 400 shown in FIG. 3 will be described.

FIG. 5 shows this differential run-length compression algorithm.

As a premise of this processing, the image information to be compressed, that is, each image information of YIQ expression, is
A maximum of N image information sequences are configured, and the differential run length compression processing is performed for each image information sequence, and the differential value after compression, the run R value, and the length L value are represented by 5 bits. I shall. Further, in the differential run-length encoding compression of the present embodiment, only the difference 0 is compressed and output by the run-length encoding, so the value of the run R is always 0, and the length of 0 is always followed by that length. L will come.

First, in this run length compression processing, n
Is set to 0, the initial value (Do) of the image information to be compressed is read (step 405), and then the initial value (Do) is output (step 410), and n is increased by +.
The next image data (Dn) is read by incrementing by 1, and 0 is set as the initial value of the length L (step 415).

Then, the calculation process of Dn-1-Dn, that is, the difference between the adjacent image data Dn-1, Dn is calculated and output (step 420), and subsequently, whether Dn and Dn-1 are equal or not. , That is, Dn-1-D in step 420
It is determined whether or not the calculation result of n is 0 (step 425).

Here, when Dn ≠ Dn−1, that is, D
If the calculation result of n-1-Dn is not 0 (step 4)
25 “No”), which indicates that there is a difference between the adjacent image data Dn−1, Dn, the n is compared with the number N of data (step 430), and n is N.
If it is larger (step 430 “No”), it means that there is no more image information to be compressed, so this run length compression processing is terminated, while if n is N or less (step 430 “ Yes "), and then, returning to step 415, n is incremented by +1 to read the next data Dn or the like, and the processing of step 415 and thereafter is performed.

On the other hand, when Dn = Dn-1, that is, Dn
If the calculation result of -1-Dn is 0 (step 425
First, the length L set to 0 is incremented by +1 (step 435), and then it is determined whether or not the length L is the maximum number 31 that can be represented by 5 bits or less (step 440). ).

Then, at this judgment, the length L is 31.
If it is determined that the value is larger than the value (step 440 "N
o ”), 31 is output as the length L (step 445), and the length L is reset to 0 (step 4).
50). Before the 31 length L output here, the difference 0 which is the run R of this length L is always output in the process of step 420.

On the other hand, when the length L is determined to be 31 or less (step 440 “Yes”), subsequently, as in step 430, the n and the number of data N are compared in size (step 440). 455), and n is larger than N (step 455 “No”), it means that there is no image information to be compressed, and the current length L
Is output (step 460) and this run-length compression processing is terminated. Even in this case, the difference 0 which is the run R of the length L is output in the process of step 420 before the length L output here.

On the other hand, when n is N or less (step 455 "Yes"), n is incremented by +1 to read the next data Dn (step 46).
5) Further, it is judged whether or not the difference between the new data and the previous data is 0, that is, Dn = Dn-1 (step 470).

If Dn ≠ Dn−1 (step 470 “No”), it means that the difference is not 0 and the continuation of the difference 0 has been interrupted.
n is output (step 475), the process returns to step 415, the next data Dn is read, and the processing from step 415 onward is performed.

On the other hand, when Dn = Dn-1, that is, when the difference between Dn-1 and Dn is 0 (step 470 "Yes"), the data of difference 0 is still continuous. Therefore, the process returns to step 435 to perform the +1 count-up process of the length L to update the length L, and the processes of step 435 and thereafter are executed.

In this way, the image information sequence consisting of N pieces of image information is subjected to differential run length encoding, that is, run length encoding of the difference 0 is performed only when the difference between adjacent image information is zero. , N pieces of image information sequences can be represented by a data sequence of a difference value other than the difference 0, a run R of the difference 0, and a length L of the difference 0.

The compression by such differential run length coding is performed for each image information of YIQ expression to be compressed.

FIG. 6 shows specific data compression by the run-length compression shown in FIG.

(A) shows a specific example in the case where run length compression is performed in the case where there are 31 or more consecutive differences.

First, the difference between adjacent pixel information in the pixel information string data D1 of 0, 1, 2, 2, ... Is calculated, and the difference information of 1, 1, 0, 0 ,. Get column D2.

In this embodiment, this difference information string D
2 is used to perform data compression by differential run-length coding.

As described with reference to FIG. 5, the differential run-length coding is the normal run-length coding, that is, the difference 0 is output as the run R only when the difference is 0 in the difference information sequence D2. It is an encoding method that counts the number of consecutive times of the difference 0 that is R and outputs the number of consecutive times as the length L, and when the difference is not 0, outputs the value of the difference as it is.

In this case, the value of the initial value of the difference information sequence D1 is output as the initial value of the run-length encoded output D3, and the difference and the length L are represented by 2's complements, and the initial value and the run R Shall be represented by an unsigned integer.

Therefore, in the case of the example shown in (a), the initial value 0 of the image information sequence D1 to be compressed is first output as the initial value, and then the differences 1 and 1 of the difference information sequence D2 are output as they are. Then, since 0 continues three times in the difference information sequence D2, the run R is 0 and the length L is 3
Is output, and the run-length encoded output is 0, 1, 1,
0, 3, ...

Therefore, in the case of the example shown in (a), since the state of the difference 0 is not so continuous, it is understood that the data is not compressed so much only by this run length compression processing.

(B) shows a specific example in which data is compressed by differential run-length coding when 31 or more differences 0 continue.

First, as shown in the figure, the image information sequence D1 is ..., 9, 5, 2, ... (2 consecutive 68 times) ...
It is assumed that 68 2s continue, such as 2, 8 ...

Then, the difference between adjacent pixel information in the image information sequence D1 is calculated to obtain the difference information sequence D2. In this figure, the difference information sequence D2 is
Although not shown, it is assumed that the difference 0 is 67 times continuous due to 68 continuous data 2.

Next, the run-length encoded output is obtained from the difference information sequence D2. At this time, in the present embodiment, each data such as the difference value and the length L is represented by 5 bits,
That is, since only a maximum number of 31 can be expressed, the maximum number of lengths L is 31, and the run R with a difference of 0 is 3
In the case of continuous one or more times, the difference 0 which is the run R and the length 31 which is the length R thereof are repeated.

Therefore, in the case of the example shown in (b), since the difference 0 continues 67 times at the 2nd data of the image information sequence D1, the run-length encoded output is ...
It is compressed as 4, -3,0,31,0,31,0,5,6, ....

Therefore, in the case of the example shown in (b), since the state of the difference 0 is large and continuous, it can be understood that the data can be sufficiently compressed only by the compression processing by the difference run length encoding. It can be seen that the compression processing by the run length coding is more effective as the number of consecutive times of the state of the difference 0 is larger.

Next, the Huffman compression process of step 500 shown in FIG. 3 will be described.

The Huffman compression process is a process of compressing the run-length coded data by Huffman coding which is a kind of entropy coding, and the data distribution of the image information file represented by a fixed bit length is calculated. Look up,
It is a table conversion process from a fixed bit length to a variable bit length, which is represented by a short bit number in order from the one with the highest occurrence frequency, and is encoded by the following procedure to perform data compression.

[0073] First, the entire image information file is read and the data distribution is checked. ． A Huffman tree (conversion table) is created based on the result of (1) so that it is represented by a short code bit in descending order of appearance frequency. ． Compress each data of the image information file read based on the Huffman tree created in. The created Huffman tree must be attached to the compressed data as a table.

Now, the procedure for creating the above Huffman tree will be described.

The Huffman tree is branched from each node in two directions, left and right. To express this in a table, two tables are prepared. However, it suffices that the number of tables is logically two. In practice, a continuous address space is divided into two, and the most significant bit of the address is used for left and right distinction. Here, the case of going to the right is "1", and the case of going to the left is "0".

The root position (address) of the Huffman tree is defined at any position in the table on the compression side and the decompression side in advance, and is normally set to zero. Also, roo
The position of t must be the same on the left and right tables.

The data width (word length) of the Huffman table is prepared to be one bit larger than the number of bits of data to be handled. Here, a large number of prepared 1 bits is taken as the MSB, and the role of the bit indicating whether or not there is a node is assigned to this bit, and the MSB of the read data is assigned.
If is less than 1, the data less than MSB indicates the position of the table to be traced next, and if MSB is 0, it is the top of the tree, and the data less than MSB represents the decompressed result.

According to the Huffman table created in this way, the Huffman compression can be executed by converting the data after the differential run-length encoding compression which is the compressed data.

Next, a concrete example of the Huffman coding compression will be briefly described. For example, assume that the following 16 data strings are Huffman-coded and compressed. e, c, d, c, d, d, e, e, a, e, f, b,
f, f, f, f

.. First, when the distribution of data in this data string is examined, it becomes a: 1 b: 1 c: 2 d: 3 e: 4 f: 5

.. A Huffman tree is created based on the result of. 7A to 7D show the procedure for creating the Huffman tree in this case.

First, as shown in (a), a tree is created by grouping two items having a low occurrence frequency. In this example, a
Since the occurrence frequency of both and b is the minimum, a tree of a and b is created, and this node (node) is set to A.

Considering the set formed in (a) as one data, the occurrence frequency of this data group A is 1 + 1 = 2, and this A and the remaining data string (c ~
In f), the smallest occurrence frequency is that A and c are both 2 and the smallest. Therefore, as shown in (b), a tree is further created with A and c, and this node is designated as B. .

Further, the frequency of occurrence of the data group B completed in (b) is (1 + 1) + 2 = 4, which is the sum of the frequency of occurrence of A and the frequency of occurrence of c, and this B and the remaining data string (d ... Since the minimum occurrence frequency in f) is 4 of B and d, as shown in (c), a tree is further created with B and d, and this node (node) is designated as C.

Furthermore, the occurrence frequency of the data group C completed in (c) is ((1 + 1) +2) + 3 = 7, which is the smallest in the occurrence frequency among this C and the remaining columns (e, f). Things are 4 of e and 5 of f, so this time (d)
As shown in, a tree is created with e and f, and this section (node
e) and C are connected to form a tree. This completes the tree for this example.

In the tree as shown in (d), among the branches of each node, 1 is for branching to the right and 0 for branching to the left.

Next, Huffman compression is performed by encoding a data string from this tree. Encoding causes the data to be encoded to be traced backwards towards the root of the tree.

Then, the above a to f are a → 0000 b → 1000 c → 100 d → 10 e → 01 f → 11, respectively.

Therefore, the original data string "e, c, d, c,
d, d, e, e, a, e, f, b, f, f, f, f "
Is "0110010100101001010000
It is expressed as 01111000011111111 ", which means that the Huffman compression is performed.

The image information compressed in the three stages of color information compression, differential run length compression, and Huffman compression as described above is stored in the character ROM 13 of FIG.

Therefore, according to the present embodiment, the color image information represented by RGB is converted into the YIQ representation, and the two components (I, Q) of the color information are each compressed to ¼, and Since the data compression by the differential run length coding and the Huffman coding is performed for each image information of the YIQ expression, the discrete cosine transform (DCT) adopted in the image compression method by JPEG or MPEG.
It is possible to obtain a compression effect equal to or higher than that of IPEG or the like without using, and the hardware configuration and software volume can be made small, and the system cost can be reduced.

Further, in the present embodiment, since the data compression is performed without using the discrete cosine transform (DCT), an image with a drastic change and a clear boundary of the drawn object, for example, black characters on a white background is used. Even in the case of image information of an image in which a large number of is written, a high data compression rate can be expected without the image of the boundary portion being distorted.

Next, the process of expanding the image information compressed as described above and displaying it will be described.

The process for expanding and displaying the compressed image information is as shown in FIG. 1 after the apparatus is started up by turning on the power or from the platform controller 3 to various operating devices (not shown). The CPU 11 receives a display control signal based on the hitting motion control signal, and the display controller 15 causes the character ROM 13 to operate according to an instruction from the CPU 11.
This is a process for reading the compressed image information from.

FIG. 8 shows a procedure for expanding and displaying the compressed image information read from the character ROM 13.

In this data decompression processing, the display controller 15 basically performs decompression processing in reverse to the three-stage image information compression processing shown in FIG. The Huffman decompression circuit 15c (see FIG. 2) refers to the Huffman table RAM 15b and performs Huffman decompression processing that is the reverse of the Huffman coding and compression processing (step 600), and then the differential run length decompression circuit 15d performs the differential run. A differential run length decompression process that is the reverse of the length coding compression process is performed (step 700), and the hardware drawing circuit 15e outputs D.
The expanded image information is stored in the VRAM 14 via the RAM controller 15f (step 800).

Therefore, the image information stored in the VRAM 14 is YIQ-expressed image information after compression processing by the average value of the color information (I, Q) shown in step 300 in FIG. ) Will be stored in the VRAM 14 in a state of being compressed to 1/4.

Then, the hardware drawing circuit 15e outputs D
The image information stored in the VRAM 14 is read out via the RAM controller 15f, and the image information read out by the YUV-RGB conversion circuit 15h is converted from YIQ representation into RGB representation (step 900). An image is displayed on the LCD display unit 2 based on the image information converted into the RGB representation.

Therefore, according to this embodiment, the luminance information (Y) of the image information represented by YIQ is restored to the state before compression, but the color information (I, Q) is restored to the state before compression. The image information, which is not completely restored and is compressed to 1/4 of that before compression, is converted from YIQ representation to RGB representation and displayed as an image as it is.

Next, each process of the data decompression process shown in FIG. 8 will be described in detail. First, the Huffman decompression process of step 600 in FIG. 8 will be described.

In the Huffman decompression process, that is, the decompression process of the data compressed by the Huffman coding, the compressed data is shifted bit by bit, and this is converted into ro of the Huffman tree.
This is done by tracing from ot.

Assuming that the Huffman tree is traced according to the rules described for the Huffman compression, if the MSB of the first input data is 1, the data at the root position in the right table is read and the MSB of the data read here is read.
When is 0, the lower bits less than the MSB of the data just read become decompressed data, and the MS of the read data
If B is 1, 1 bit is further acquired from the next data, and that bit is used as the left / right distinction of the next Huffman table, and the data of the Huffman table at the position represented by the bits less than the MSB of the previously read data. Read. Then, such a work is repeated to trace the end of the Huffman table.

A specific example of the Huffman decompression process will be described below.

This decompression processing is performed by the Huffman decompression circuit 15c (see FIG. 2) in the display controller 15, and the Huffman decompression circuit 15c outputs the word length image information 5b.
Compress to it. The Huffman table at this time is 6b
Since it is necessary to prepare two types of Left and Right with an it width of 31 and a size of 6 bits in total.
A memory of × 31 × 2 = 372 bits is required, the address of the Huffman table output from the display controller 15 is 7 bits (bit6 to bit0), and Left and Right are distinguished by the most significant bit (bit6).

When the most significant bit (bit5) of the Left and Right tables is 0, the lower 5
The information of bits (bit4 to bit0) becomes the decoded data as it is, and when the most significant bit is 1, the lower 5 bits
The information of t (bit4 to bit0) indicates the address of the next table.

FIGS. 9A and 9B show a specific example of the Huffman tree and data stored in the memory according to the Huffman tree.

Here, the root is set to 20 for convenience of explanation.
It is assumed that the image information “02” is compressed to “011” based on this Huffman tree.

. First, since the carry obtained by shifting "011" to the left is "0", the Left table shown in (b) is referred to. The beginning of extension is (a)
Since it is traced from the root position of the Huffman tree shown in,
The address 20 of the Left table is read. Le
“61H” is read from the address 20 of ft.
This is MSB = 1, bit6 to bit0 = 21H, and M
Since SB = 1 indicates that it is not the end of the Huffman tree, it indicates that the next node (node) is at 21H of the table at bit6 to bit0.

.. Since the end of the Huffman tree could not be reached, the compressed data was further shifted to the left and shifted by 1 bit, so the rest was 2 bits of "11". Get "1" for carry. Ri shown in (b) because the carry is "1"
Referring to the ght table, its position was obtained at 21
Since it is H, “62H” is read from Right 21. This is MSB = 1, bit6 to bit0 = 2
2H indicates that MSB = 1 is not the top of the tree, so the next section (node) is set at bit6 to bit0.
Is at 22H in the table.

.. Like the above, since the end of the tree could not be reached, the compressed data is further shifted to the left, and
Since it has been bit-shifted, the rest is 1 bit of "1", which is shifted to the left to obtain "1" for the carry. Ri shown in (b) because the carry is "1"
Refer to the ght table, the position was obtained in 22
Since it is H, “02H” is read from Right 22. This is MSB = 0, bit6 to bit0 = 0
It becomes 2H, which means that MSB = 0 and thus the end of the tree, and bit 6 to bit 0 indicates that the target decompressed data is 02H.

With the above, the operation of the Huffman decompression processing by the Huffman decompression circuit 15c is completed.

Next, the differential run length expansion processing of step 700 in FIG. 8 will be described.

FIG. 10 shows an algorithm of the differential run-length decompression process, that is, the decompression process which is the reverse process of the differential run-length coding compression.

This differential run length expansion processing is performed by the differential run length expansion circuit 15d in the display controller 15. Basically, the processing opposite to the compression processing by the differential run length encoding shown in FIG. The data after the run length compression processing is expanded to N data before the compression.

First, the differential run length decompression circuit of the display controller 15 sets i to 0 by starting this processing, and sets the initial value D0 (i = 0) of the Huffman decompressed differential run length compressed data. ) Is read (step 705), and then its initial value D0 is output as the initial value of the data before differential run-length encoding compression, and
The n is set to 1 (step 710).

Then, while reading the next data D,
i is incremented by +1 (step 715), the decompressed data Di-1 immediately before is added to the data D newly read from the differential run-length compressed data, and set as new decompressed data Di. (Step 720),
Then, it is judged whether or not the read data D is 0, that is, the run R showing the difference 0 (step 725).

Here, the read data D is not 0,
That is, when it is determined that the data D is not the run R indicating the difference 0 (step 725 “No”), there is a difference between the data before compression, and the data is compressed by the difference run length conversion. Since it indicates that there is no data, the data Di of the value calculated in the above step 720 is output as the data Dn before compression, and n is incremented by +1 (step 730), and then n is the number of data before compression. It is determined whether N is exceeded (step 750).

When it is determined that n exceeds the number N of data before compression (step 750 "Yes"),
Since all the data that has been subjected to the differential run length compression processing has been expanded to the data before the compression, this expansion processing is ended. On the other hand, n is the number of data before compression N
If it is determined that the value does not exceed (step 750
“No”), which indicates that all the data that has been differentially run-length compressed has not been decompressed to the data before the compression. Therefore, the process returns to step 715 and the Huffman decompression, that is, the difference is performed. The next run-length compressed data D is read, i is incremented by +1 and the processing from step 715 onward is repeated.

On the other hand, when it is judged that the read data D is 0, that is, the run R indicating the difference 0 (step 725 “Yes”), the difference between the data before compression is 0, Since it is shown that the data continuous with the difference 0 is compressed by the difference run length conversion, the length L of the difference 0, which is the next data D, is further read (step 735).

In this case, first, step 72
The data Di calculated by 0 is output as the uncompressed data Dn, n is further incremented by +1 and the read data D indicating the length L with a difference of 0 is decremented by -1 (step 740). -1 It is determined whether the decremented data D has become smaller than 0 (step 745).

If the new data D is not smaller than 0, that is, if the data D indicating the length L with a difference of 0 is judged to be 0 or more (step 745 "N
o ″), which means that the difference 0 is still continuous, the process returns to step 740 again, and the data Di calculated in step 720 is output as the uncompressed data Dn, and n is further incremented by +1. , And the difference is 0
The read data D, which is the length L of, is decremented by -1.

As a result, it is possible to output the continuous data Di before compression with the difference 0 for the length L times of the difference 0.

On the other hand, if it is judged that the data D after -1 subtraction becomes smaller than 0 (step 745).
“Yes”), which means that the continuous processing with the difference of 0 has ended, so that, similarly to the processing after the processing of step 730, n which is subsequently incremented by +1 in step 740 is the number of data before compression N It is determined whether or not the value has exceeded (step 750).

If it is determined that n does not exceed the number N of data before compression (step 750 "N
o ”), which indicates that there is data D that has been differentially run-length compressed, the process returns to step 715, the next Huffman-decompressed data D is read, and i is incremented by +1. Step 715 again
While repeating the following process, when it is determined that n exceeds the number N of data before compression (step 75)
0 “Yes”), the decompression process of the differential run length compression is ended.

If such differential run-length expansion processing is performed for each piece of image information in the Huffman expanded YIQ expression, for example, differential run-length compression processing is performed as shown in FIGS. 6 (a) and 6 (b). The data D3 can be decompressed to the uncompressed data D1.

Next, the process of storing the Huffman-decompressed and differential run-length-decompressed data in the VRAM 14 at step 800 in FIG. 8 will be described.

FIG. 11 shows a data storage state in this VRAM 14.

This VRAM 14 has 15 bits as shown in the figure.
Two DRAMs 14a, 14 that store data in bits
b, each of which stores three pieces of image information represented by 5 bits at the same address.

For example, in the DRAM 14a, differential run length expanded image information such as "Y00, I00, Q00" is stored at the highest address in the figure, and "Y10" is stored at the next address. , Y01, Y11 ", and the color information of each luminance information Y10, Y01, Y11 is not stored.

This is the color information I00, Q00 of the luminance information Y00.
Represents the luminance information Y10, Y01, Y11 by compressing the color information.
Since the average value of the color information of is used, each luminance information Y1
The color information of 0, Y01, Y11 is the color information I0 of the luminance information Y00.
This is because the values are the same as 0 and Q00, and the values of the color information I00 and Q00 can be used.

Therefore, in the DRAM 14a, "Y40, I20, Q20" are stored next, and subsequently the luminance information "Y50, Y41, Y51" having the common color information I20, Q20 is stored.

The DRAM 14b includes the DRAM 14
Similarly to a, first, "Y20, I10, Q10", and then luminance information "Y30, Y2" which is common to the color information I10, Q10.
1, Y31 ", then" Y60, I30, Q30 ", and subsequently luminance information" Y70, Y61, Y "which is common to the color information I30, Q30.
It is stored as 71 ”.

Therefore, according to the present embodiment, the luminance information Y is unchanged and the two components of the color information I and Q are compressed to ¼, respectively. If each YIQ is set to 1, and the total is 3, the data amount after compression is 1 + 1/4 + 1/4 = 1.5.
The storage capacity of 14 is 1/2 times that of the conventional one, and the memory cost can be reduced.

The display controller 15 is an LCD
When displaying an image on the display unit 2, the image information in YIQ expression stored in the VRAM 14 is read and converted into image information in RGB expression (step 900). At that time, VRA
Since the image information of the YIQ expression stored in the M14 is stored as shown in FIG. 11, the access to the VRAM 14 which is conventionally required four times to read the image information for four pixels is performed twice. Access is enough.

That is, assuming that the image information is read for each pixel by one access, it is necessary to read the image information for four pixels four times in the conventional case, but in the present embodiment, it is necessary. , For example, in the case of the VRAM 14a shown in FIG.
"Y00, I00, Q00" can be read by the second access, and "Y10, Y01, Y11" can be read subsequently by the second address, and the color information I, Q of each luminance information Y10, Y01, Y11 can be read.
Is not read directly, but the brightness information Y10, Y01,
The color information I and Q of Y11 is the color information I00 and Q00 of the luminance information Y00.
Since the same value can be used as the color information of each luminance information Y10, Y01, Y11 in the display controller 15,
Since the image information for four pixels is read out, the access can be completed twice as much as the conventional one.

Therefore, according to the present embodiment, the image information compressed by the Huffman coding and the differential run length coding is expanded, but the color information compressed after being converted into the YIQ representation is not expanded and is stored in the VRAM 14. Store and LC
Since the display on the D display unit 2 is performed, the storage capacity of the VRAM 14 becomes half that of the conventional one, and the number of accesses to the image information stored in the VRAM 14 is reduced, so that the display speed of the image can be increased. it can.

[0137]

As described above, in the present invention, color image information is separated and converted into luminance information and color information, the color information is compressed, and the differential run length code is applied to each image information. And Huffman coding are used for data compression, so JPEG and MP
Without using the discrete cosine transform (DCT) used in the image compression method by EG, it is possible to obtain a compression effect equal to or higher than that of IPEG, etc., and reduce the hardware configuration and software volume. It is possible to reduce the system cost.

In the present invention, the discrete cosine transform (D
Since I tried to compress the data without using (CT),
Even in the case of image information where the change is extreme and the boundary of the drawn object is clear, for example, the image in which many black characters are written on a white background, the image at the boundary is not distorted and the data compression rate is high. Can be expected.

Further, in the present invention, the image information compressed by the Huffman coding and the differential run-length coding is expanded, but the compressed color information is stored in the image memory without being expanded and is displayed on the display unit. Since it was made to display,
The storage capacity of the image memory is reduced as compared with the conventional one, and the number of times the image information stored in the image memory is accessed is reduced, so that the display speed of the image can be increased.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a configuration of an embodiment of an image display device according to the present invention.

FIG. 2 is an explanatory diagram showing a detailed internal configuration of a display controller.

FIG. 3 is a flowchart showing an outline of image information compression processing.

FIG. 4 is an explanatory diagram showing a state of image information when converting and compressing RGB representation into YIQ representation.

FIG. 5 is an explanatory diagram showing a run length compression algorithm.

FIG. 6 is an explanatory diagram showing specific data compression by run-length compression.

FIG. 7 is an explanatory diagram showing an example of creating a Huffman tree.

FIG. 8 is a flowchart showing a procedure of decompression processing of compressed image information.

FIG. 9 is an explanatory diagram showing a specific example of a Huffman tree and data stored in a memory according to the Huffman tree.

FIG. 10 is an explanatory diagram showing an algorithm of decompression processing of this differential run-length encoding.

FIG. 11 is an explanatory diagram showing a data storage state in the VRAM.

[Explanation of symbols]

 1 display module 2 LCD display unit 3 units control unit 11 CPU 12 program ROM 13 character ROM 14 VRAM 15 display controller 15b Huffman table RAM 15c Huffman expansion circuit 15d differential run length expansion circuit 15h YUV-RCB conversion circuit 15m LCD controller

Claims (8)

[Claims] 1. An image information compression method for compressing color image information, wherein the color image information is separated and converted into luminance information and color information, and only the separated and converted color information is compressed. Image information compression method. 2. An image information compression method for compressing image information consisting of an image information sequence, wherein a difference between adjacent image information in the image information sequence is calculated, and if there is a difference, a difference indicating the difference. The image information compression method is characterized in that the above-mentioned image information sequence is compressed using run information indicating that there is no difference when there is no difference and length information indicating the number of consecutive times without difference, as information. 3. An image information compression method for compressing color image information, wherein the color image information is separated and converted into luminance information and color information, and only the separated and converted color information is compressed and separated and converted. Luminance information and for each image information string of each image information of the compressed color information, the difference between adjacent image information is calculated, and if there is a difference, the difference information indicating the difference is output, If there is no difference, the run information indicating that there is no difference and the length information indicating the number of consecutive times without difference are compressed, and further Huffman compression is performed for each image information sequence after compression. Information compression method. 4. The color image information is arranged in a matrix based on the position of the color image, and the compression of the color information is performed in a predetermined size in the adjacent x direction or y direction of the image information arranged in the matrix. The image information according to claim 1 or 3, wherein an average is taken for each of a plurality of color information for each size or for each matrix of a predetermined size, and the average value is used as a value of each color information. Compression method. 5. In an image display device for compressing and storing color image information and reading the compressed image information to display a color image on a display, the color image information is separated into luminance information and color information. Image information converting means for converting the color information, color information compressing means for compressing only the color information separated and converted by the image method converting means, luminance information separated and converted by the image information converting means, and the color information compression Image information storage means for storing the color information compressed by the means, and the luminance information and color information of each pixel to be displayed on the display are read out from the image information storage means, converted into color image information, and displayed. An image display device, comprising: a display control unit for displaying a color image on the display unit. 6. An image display device for compressing and storing image information consisting of an image information sequence, and reading the compressed image information to display an image on a display, wherein each adjacent image in the image information sequence is The difference between the information is calculated, and when there is a difference, the difference information indicating the difference is set, and when there is no difference, the run information indicating that there is no difference and the length information indicating the number of consecutive times without difference are set. ,
A differential run-length compression means for compressing the image information sequence, and a Huffman tree is created based on the image information sequence compressed by the differential run-length compression means.
A Huffman compression means for Huffman-compressing the image information string according to the Huffman tree, an image information string storage means for storing the image information string compressed by the Huffman compression means, and an image stored in the image information string storage means. The information sequence is read out, and the Huffman decompression means for decompressing the image information sequence before Huffman compression according to the Huffman tree, and the image information sequence decompressed by the Huffman decompression means are processed by the reverse processing of the differential run-legging means. A differential run-length expansion unit for expanding the image information sequence before processing, and a display control for reading out each image information forming the image information sequence expanded by the differential run-length expansion unit and displaying an image on the display. An image display device comprising: 7. An image display device for compressing and storing color image information and reading the compressed image information to display a color image on a display, wherein the color image information is separated into luminance information and color information. Image information converting means for converting, color information compressing means for compressing only color information separated and converted by the image method converting means, luminance information separated and converted by the color information compressing means, and compressed color For each image information string of each image information of information,
The difference between adjacent image information in each image information sequence is calculated, and if there is a difference, it is used as difference information, and if there is no difference, run information indicating that there is no difference and no difference With the length information indicating the number of consecutive times, the differential run length compression means for compressing each of the image information sequences, and each image information sequence compressed by the differential run length compression means, based on each image information. Huffman compression means for creating a Huffman tree and Huffman compressing the image information sequence according to the Huffman tree, image information sequence storage means for storing each image information sequence compressed by the Huffman compression means, and the image information Each image information sequence stored in the column storage means is read out and expanded to each image information sequence before Huffman compression according to the Huffman tree. Mann decompression means, and differential run length decompression means for decompressing each image information sequence decompressed by the Huffman decompression means to each image information sequence before the process by a process reverse to that of the differential run length compression process. Display control means for converting each image information of luminance information and hue information forming each image information sequence expanded by the differential run-length expansion means to color image information and displaying a color image on a display, An image display device comprising. 8. The color image information is arranged in a matrix based on the position of the color image, and the compression of the color information is performed in a predetermined size in the adjacent x direction or y direction of the image information arranged in the matrix. The image display according to claim 5 or 7, wherein an average is taken for each of a plurality of color information for each size or for each matrix of a predetermined size, and the average value is used as the value of each color information. apparatus.