CA2300326C - Image data compression, decompression and display device - Google Patents
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Abstract
An image data compressing device includes: a maximal value extracting unit and a minimal value extracting unit that respectively extract a maximal value anal a minimal value from pixel values in a prescribed region of image data; a level decision unit that determines quantization levels of the pixel values in the prescribed region based on the maximal and minimal values extracted; and a comparison unit that compares the images data with the quantization levels and outputs quantized data. Since the comparison unit quantizes the pixel value in the prescribed region by comparing the image data with the quantization levels, it is possible to compress the image data with a simple configuration.
Description
IMAGE DATA COMPRESSION, DECOMPRhSSION AND DISPLAY DEVICE
~i BACKGROUND OF THE INVENTION
Field of the Invention The present invention relates to image data compressing and decompressing techniques Bused for three dimensional graphics or the like, and more particularly, to a:n image data compressing device that compresses image data taking advantage of continuity of pixel values of the image data, an image data decompressing device that regenerates image data from the compressed image data, and an image display device using the mentioned devices.
Description o:f the Background Art 1;i In recent years, display devices used for computers, such as a cathode ray tube (CRT) and a liquid crystal device (LCD), have improved in resolution, and have displayed image data ~2th increased data amounts.
Accordingly, there has been a need for image memories with larger capacities.
~i BACKGROUND OF THE INVENTION
Field of the Invention The present invention relates to image data compressing and decompressing techniques Bused for three dimensional graphics or the like, and more particularly, to a:n image data compressing device that compresses image data taking advantage of continuity of pixel values of the image data, an image data decompressing device that regenerates image data from the compressed image data, and an image display device using the mentioned devices.
Description o:f the Background Art 1;i In recent years, display devices used for computers, such as a cathode ray tube (CRT) and a liquid crystal device (LCD), have improved in resolution, and have displayed image data ~2th increased data amounts.
Accordingly, there has been a need for image memories with larger capacities.
2~~ Further, expansion of three dimensional (3D) graphics requires, not only memories for retaining color data of red (R,), green (G) and blue (B), each of several bit lengths, for each pixel of image data, but also a memory for retaining z-coordinate data indicating depth information of images as well as a memory for retraining a data indicating transparency of objects.
25 Thus, overall image memory capacity necessary for expansion of image data in 3D graphics is larger t;h~an that for two dimensional graphics.
As explained above, image memos°ies of large capacity are required because of increased resolution of display devices, and image memories of still larger capacity'are required to expand 3D graphics. This makes it 30 difficult to arrange the image memories on c:hip. In addition, since the data amount being transferred between circuits for expanding 3D graphics and image memories increases, such data transfer has become a stumbling block hindering speeding of 3D graphics processing.
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SUMMARY OF THE INVE:~1TION
An object of the present invention is to provide an image compressing device capable of compressing image data with a simple configuration.
Another object of the present invention is to provide an image decompressing device capable of restoring image data with a simple configuration.
A further object of the present invention is to provide an image display device requiring an image memory with less capacity for expansion of image data.
According to an aspect of the present invention, an image data compressing device ;includes: an extracting unit that extracts two reference values from pixel values in a prescribed region of image data; and a quantization unit that quantizes the pixel value in the prescubed region based on the two reference values extracted by the extracting unit.
The pixel value in the prescribed region is quantized by the quantization unit based on the two values extracted by the extracting unit.
Therefore, the image data can be compressed with a simple configuration.
According to another aspect of the present invention, an image data decompressing device includes: an extracting unit that extracts two 20~ reference values and quant:ized data of pixel values in a prescribed region from compressed image data; and a decompressing unit that restores the pixel value in the prescribed region based on the two reference values and the quantized data extracted by the extracting unit.
The pixel value in the prescribed region is restored by the 25. decompressing unit based on the two reference values and the quantized data extracted by the extracting unit. Therefore, the image data can be restored with a simple configuration.
According to ~~ further aspect of the present invention, an image display device includes: an image data generating unit that generates 30 image data; a first extracting unit that extracts two reference values from pixel values in a prE~scribed. region of the image data generated by the image data generating unit; a quantization unit that quantizes the pixel value in the prescribed region based on the two reference values extracted by the first extracting unit; an image memory that stores the two reference values extracted by the first extracting unit and the pixel value in the prescribed region quantized by the quantization unit as compressed image data; a second extracting unit that extracts two reference values and ai quantized data of pixel values in a prescxzbed region from the compressed image data stored i:n the image memory; a decompressing unit that restores the pixel value in the prescubed region based on the two reference values and the quantized data extracted by the second extracting unit; and a display unit that displays on a display screen based on the pixel value in 1() the prescribed region restored by the decompressing unit.
The image memory :Mores the two reference values extracted by the first extracting unit; and the pixel value in the prescribed region quantized by the quantization unit as the compressed image data. Therefore, it is possible to reduce the capacity of the image memory.
15 The foregoins; and other objects, features, aspects and advantages of the present inventi~~n will lbecome more apparent from the following detailed description of the :present invention when taken in conjunction with the accompan~~ing drawings.
BRIEF DESCRIPT:~ON OF' THE DRAWINGS
20 Figs. 1A to 1'C illustrate the concept of image data compression according to a first embodiment of the present invention.
Fig. 2 shows a schematic configuration of an image data compressing device according to the first embodiment of the present invention.
Fig. 3 shows a schematic configuration of an image data 2~ decompressing device according to a second embodiment of the present invention.
Fig. 4 shows a schematic configuration of an image display device according to a third embodiment of the present invention.
DESCRIPTION OF' THE PREFERRED EMBODIMENTS
30 First Embodiment Figs. 1A to 1C illustrate the concept of an image data compressing process according t~o the first embodiment of the present invention. As shown in Fig. 1A, the image data compressing process according to the present embodiment is performed for each pixel in a prescribed region within the image data. Here, a process of compressing adjacent four pixels (a, b, c, d) will be described as an example of the image data compressing process.
Four pixels (hereinafter, also referred to as a "pixel block") shown in Fig. 1A respectively include R, G, B and a data indicating transparency (they are collective',~y called "pixel data"). For example, pixel a includes pixel data Ra, Ga, ~Ba and aa, as shown in Fig. 1B. Assuming that each of pixel data (R, G, B and a) its expressed with 8 bits, the data amount of one pixel block becomes 128 bits (8 bits x 16).
Now, a maximal value and a minimal value are extracted for each pixel data, and the pixel data are quantized for each pixel. If the quantized data are expressed with 2 bits, the quantization can be performed with four stages from level 0 to level 3. For example, assuming that R values of pi~~els a to~ d are {4, 2, 8, 10}, the maximal value (Rmax) is "10", and the minimal value (R.min) is "2". Dividing their difference (10 -2 = 8) by the number of above-described stages (4), the width of one stage of "2" is obtained. Tllus, if 2; ~ R value < 4 (level 0), "00" is given as the quantized data; if ~( ~ R value < G (level 1), "O1" is given; if G ~ R value <
8 (level 2), "10" is given; and if 8 ~ R value ~ 10 (level 3), "11" is given as the quantized data. As a result, the quantized R values (R,quan) of respective pixels bE~come {O1, 00, 11, 11}. Therefore, the R values of four pixels can be expressed with 24 bits in total, including the maximal value of 8 bits, the mini~rial value of 8 bits, and the quantized data of 8 bits.
The G value, B value and a value are also quantized in the same manner.
By quantizing all tb.e R, G, B and a values as described above, pixel data for four pixels can be expressed with 9G bits. In the actual image data, differences between pixels tend to be smaller because of high continuity of the image data. Thus, it is possible to improve precision at the time of regenezation.
The number of pixels within a pixel block has been set as 4 (2x2) in the image data compression described above. However, if the number of pixels is made as 9 (3x3), each pixel data reduces from 72 bits (8 bits x9) to 34 bits (8 bits + 8 bits + 2 bits x9). If the number of pixels becomesl6 (4x4), each pixel data reduces from 128 bits (8 bits x1G) to 48 bits (8 bits + 8 bits +
2 bits x16). In thi:~ way, the effect of image data compression increases as the number of pixels in a pixel block unit increases.
Fi Fig. 2 is a block diagram showing a schematic configuration of an image data compressing device according to the present embodiment. The image data compressing device includes: a data buffer 1 that temporarily retains image data; a maximal value extracting unit 2 that compares input image data and extracts maximal value data; a minimal value extracting unit 3 that compares input image data and extracts minimal value data; a level decision unit 9~ that determines quantization levels (level 0 - level 3) based on the maximal value data extracted by maximal value extracting unit 2 and the minimal value data extracted by minimal value extracting unit 3; comparison units 5 - 8 that compare input image data with the lfi quantization levels output from level decision unit 4 to output quantized values (quan-a - quan-d); and an encoder 9 that encodes the maximal value data, the minimal value data, and the quantized data output from comparison units 5 - 8.
The image data are usually processed in a raster unit, whereas they are processed in a polygon unit in 3D graphics. Thus, data buffer 1 temporarily stores input data such that the data are arranged into pixel block units as shown in Fig;. 1A. Once a pixel block of data is available, data buffer 1 outputs the data in the pixel block unit.
Maximal value extracting unit 2 extracts the maximal value from the 2fi data in the pixel black unit, and outputs the value to level decision unit 4.
Minimal value extr;~cting unit 3 extracts the minimal value from the data in the pixel block unit, and outputs the value to level decision unit 4.
Level decision unit 4 determines the above-described levels 0 - 3 (LO - L3) based on the maximal and minimal value data, and outputs the determined levels.
Comparison units 5 ~- 8 each compare the pixel data output from data buffer 1 with levels LO - L3 input thereto. For example, comparison unit 5 inputs pixel data for pixel a shown in Fig. 1A, and compares the input data with LO - L3 to quantize the pixel data. Comparison unit 5 then outputs the quantized data to encoder 9.
Encoder 9 receives the maximal value output from maximal value extracting unit 2, the minimal value output from minimal value extracting unit 3, and quantiz~ed data (quan-a - quan-d) output from comparison units 5 - 8, and shapes the data into a prescribed format for output.
As explained above, according to the image data compressing device of the present embodiment;, maximal and minimal values and quantized data of pixel data are extracted and output. Thus, image data compression can be readily performed with such a simple configuration as described above.
Second Embodiment Fig. 3 is a block diagram showing a schematic configuration of an image data decompressing device according to the second embodiment of the present invention. The image data decompressing device includes: a decoder 11 that inputs compressed image data, and separates and outputs maximal value data, minimal value data and quantized data quan-a -quan-d of pixel data; a level decision unit 12 that determines quantization levels (level 0 - level 3) based on the maximal and minimal value data separated by decodE~r 11; select units 13 - 16 that select the quantization levels output from level decision unit 12 based on quantization data quan-a - quan-d output from decoder 11, to output as respective pixel data (Db -Dd); and an output unit 17 that outputs pixel data.
Decoder 11 inputs the compressed image data shown in Fig. 1C, and separates the maximal value data, the minimal value data and the quantized data quan-a - quan-d for each pixel data. For example, when the R values as shown in F:ig. 1C are input, maximal value Rmax, minimal value Rmin and Rquan (R,quan-a - Rquan-d) are separated. Decoder 11 then outputs maxiirial value Rmax and minimal value Rmin to level 3C1 decision unit 12, and outputs quantized data li,quan-a - Rquan-d to select units 13 - 16, respectively.
Level decision unit 12 determines and outputs the above-described levels 0 - 3 (LOD - L3D) based on the maximal and minimal values. Select units 13 - 16 select and output pixel data (restored data) that correspond to quantized data quan-a - quan-d. For example, if select unit 13 receives quantized data Rquan-a for the R value of pixel a, it outputs data value Da corresponding to the quantized data Rquan-a to output unit 17. Output .5 unit 17 receives, from seleca units 13 -16, data values Da - Dd corresponding to qmantized~ data Rquan-a - Rquan-d, and outputs them as pixel data. This p~cocess i:> sequentially performed for the G value, B value and a, value, so than the R, G, B and a, values of each pixel can be restored.
In the above-described embodiments, RGB and a values have been 11) compressed/decompressed. However, other data can be compressed in the same manner. For example, in the case where a Z buffer method is used for hidden-sunace removal in three dimensional gzaphics, maximal and minimal Z values ~r~ay be extracted so that the Z values of pixels can be quantized for compression.
15 As explained above, according to the image data decompressing device of the present embodiment, maximal and minimal value data as well as quantized data of pixel data are separated from compressed image data, and the pixel data are restored based on these data. Therefore, image data restoration can be readily performed with a simple configuration as 21) described above.
Third Embodiment Fig. 4 is a block diagram showing,a schematic configuration of an image display device including a three dimensional graphics accelerator according to the third embodiment of the present invention. The image 2;i display device includes: a central processing unit (CPU) 2 that peuorms overall control of the image display device; a main memory 22; a graphics accelerator 23; a control circuit 24 that controls generation of a timing signal for main memory 22 and graphics accelerator 23 and data input/output; an image memory 25 used for expansion of the image data;
31) and a cathode ray tube (CI~'"T) 2G on which an image is displayed.
Further, graphics accelerator 23 includes: a renderer 31 that generates image data by performing calculation of shape and color (hidden-surface processing, color tome calculation) of an object to be displayed on a _7_ screen based on a va.x-iety of models including a motion model; an image data compressing unit 32 that compresses the image data based on the shape and color of the objecit calculated by renderer 31; a memory controller 33 that wxltes the inxage data compressed by image data compressing unit 32 into image memory 25 and reads the compressed image data out of image memory 25; a:n image data decompressing unit 34 that restores original image data :from the compressed image data read out of image memory 25; a rastex:izer 35 vthat converts the image data output from image data decompressing unit 34 into a display format suitable for CRT 26; and a digital/analog converter (I)AC) 3G that converts digital signals output from rasterizer 35 to~ analog' signals. As processing by renderer 31 and rastex~izer 35 are well known and are not directly related to the present invention, they are not described in detail herE~.
For image data compressing unit 32 and image data decompressing unit 34, the image data compressing device and the image data decompressing device descx7ibed in the first and second embodiments are used. Thus, by applying the image data compressing device and the image data decompressing device i~o the graphics accelerator, the data amount required to represent the irr~age data, and hence, the capacity of image memory 25, can be reduced. Though an image display device with a three dimensional graphics accelerator has been described by way of example in the present embodiment, the present invention can be applied to other devices displaying images on other types of display screens.
Although the present invention has been described and illustrated in detail, it is clearly understood that the same is by way of illustration and example only and is not to be taken by way of limitation, the spirit and scope of the present invention being limited only by the terms of the appended claims.
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25 Thus, overall image memory capacity necessary for expansion of image data in 3D graphics is larger t;h~an that for two dimensional graphics.
As explained above, image memos°ies of large capacity are required because of increased resolution of display devices, and image memories of still larger capacity'are required to expand 3D graphics. This makes it 30 difficult to arrange the image memories on c:hip. In addition, since the data amount being transferred between circuits for expanding 3D graphics and image memories increases, such data transfer has become a stumbling block hindering speeding of 3D graphics processing.
...~ . ..... . . . .. n... .,_.. ~ a r. .....,. _ ~ ,.... .. ..
SUMMARY OF THE INVE:~1TION
An object of the present invention is to provide an image compressing device capable of compressing image data with a simple configuration.
Another object of the present invention is to provide an image decompressing device capable of restoring image data with a simple configuration.
A further object of the present invention is to provide an image display device requiring an image memory with less capacity for expansion of image data.
According to an aspect of the present invention, an image data compressing device ;includes: an extracting unit that extracts two reference values from pixel values in a prescribed region of image data; and a quantization unit that quantizes the pixel value in the prescubed region based on the two reference values extracted by the extracting unit.
The pixel value in the prescribed region is quantized by the quantization unit based on the two values extracted by the extracting unit.
Therefore, the image data can be compressed with a simple configuration.
According to another aspect of the present invention, an image data decompressing device includes: an extracting unit that extracts two 20~ reference values and quant:ized data of pixel values in a prescribed region from compressed image data; and a decompressing unit that restores the pixel value in the prescribed region based on the two reference values and the quantized data extracted by the extracting unit.
The pixel value in the prescribed region is restored by the 25. decompressing unit based on the two reference values and the quantized data extracted by the extracting unit. Therefore, the image data can be restored with a simple configuration.
According to ~~ further aspect of the present invention, an image display device includes: an image data generating unit that generates 30 image data; a first extracting unit that extracts two reference values from pixel values in a prE~scribed. region of the image data generated by the image data generating unit; a quantization unit that quantizes the pixel value in the prescribed region based on the two reference values extracted by the first extracting unit; an image memory that stores the two reference values extracted by the first extracting unit and the pixel value in the prescribed region quantized by the quantization unit as compressed image data; a second extracting unit that extracts two reference values and ai quantized data of pixel values in a prescxzbed region from the compressed image data stored i:n the image memory; a decompressing unit that restores the pixel value in the prescubed region based on the two reference values and the quantized data extracted by the second extracting unit; and a display unit that displays on a display screen based on the pixel value in 1() the prescribed region restored by the decompressing unit.
The image memory :Mores the two reference values extracted by the first extracting unit; and the pixel value in the prescribed region quantized by the quantization unit as the compressed image data. Therefore, it is possible to reduce the capacity of the image memory.
15 The foregoins; and other objects, features, aspects and advantages of the present inventi~~n will lbecome more apparent from the following detailed description of the :present invention when taken in conjunction with the accompan~~ing drawings.
BRIEF DESCRIPT:~ON OF' THE DRAWINGS
20 Figs. 1A to 1'C illustrate the concept of image data compression according to a first embodiment of the present invention.
Fig. 2 shows a schematic configuration of an image data compressing device according to the first embodiment of the present invention.
Fig. 3 shows a schematic configuration of an image data 2~ decompressing device according to a second embodiment of the present invention.
Fig. 4 shows a schematic configuration of an image display device according to a third embodiment of the present invention.
DESCRIPTION OF' THE PREFERRED EMBODIMENTS
30 First Embodiment Figs. 1A to 1C illustrate the concept of an image data compressing process according t~o the first embodiment of the present invention. As shown in Fig. 1A, the image data compressing process according to the present embodiment is performed for each pixel in a prescribed region within the image data. Here, a process of compressing adjacent four pixels (a, b, c, d) will be described as an example of the image data compressing process.
Four pixels (hereinafter, also referred to as a "pixel block") shown in Fig. 1A respectively include R, G, B and a data indicating transparency (they are collective',~y called "pixel data"). For example, pixel a includes pixel data Ra, Ga, ~Ba and aa, as shown in Fig. 1B. Assuming that each of pixel data (R, G, B and a) its expressed with 8 bits, the data amount of one pixel block becomes 128 bits (8 bits x 16).
Now, a maximal value and a minimal value are extracted for each pixel data, and the pixel data are quantized for each pixel. If the quantized data are expressed with 2 bits, the quantization can be performed with four stages from level 0 to level 3. For example, assuming that R values of pi~~els a to~ d are {4, 2, 8, 10}, the maximal value (Rmax) is "10", and the minimal value (R.min) is "2". Dividing their difference (10 -2 = 8) by the number of above-described stages (4), the width of one stage of "2" is obtained. Tllus, if 2; ~ R value < 4 (level 0), "00" is given as the quantized data; if ~( ~ R value < G (level 1), "O1" is given; if G ~ R value <
8 (level 2), "10" is given; and if 8 ~ R value ~ 10 (level 3), "11" is given as the quantized data. As a result, the quantized R values (R,quan) of respective pixels bE~come {O1, 00, 11, 11}. Therefore, the R values of four pixels can be expressed with 24 bits in total, including the maximal value of 8 bits, the mini~rial value of 8 bits, and the quantized data of 8 bits.
The G value, B value and a value are also quantized in the same manner.
By quantizing all tb.e R, G, B and a values as described above, pixel data for four pixels can be expressed with 9G bits. In the actual image data, differences between pixels tend to be smaller because of high continuity of the image data. Thus, it is possible to improve precision at the time of regenezation.
The number of pixels within a pixel block has been set as 4 (2x2) in the image data compression described above. However, if the number of pixels is made as 9 (3x3), each pixel data reduces from 72 bits (8 bits x9) to 34 bits (8 bits + 8 bits + 2 bits x9). If the number of pixels becomesl6 (4x4), each pixel data reduces from 128 bits (8 bits x1G) to 48 bits (8 bits + 8 bits +
2 bits x16). In thi:~ way, the effect of image data compression increases as the number of pixels in a pixel block unit increases.
Fi Fig. 2 is a block diagram showing a schematic configuration of an image data compressing device according to the present embodiment. The image data compressing device includes: a data buffer 1 that temporarily retains image data; a maximal value extracting unit 2 that compares input image data and extracts maximal value data; a minimal value extracting unit 3 that compares input image data and extracts minimal value data; a level decision unit 9~ that determines quantization levels (level 0 - level 3) based on the maximal value data extracted by maximal value extracting unit 2 and the minimal value data extracted by minimal value extracting unit 3; comparison units 5 - 8 that compare input image data with the lfi quantization levels output from level decision unit 4 to output quantized values (quan-a - quan-d); and an encoder 9 that encodes the maximal value data, the minimal value data, and the quantized data output from comparison units 5 - 8.
The image data are usually processed in a raster unit, whereas they are processed in a polygon unit in 3D graphics. Thus, data buffer 1 temporarily stores input data such that the data are arranged into pixel block units as shown in Fig;. 1A. Once a pixel block of data is available, data buffer 1 outputs the data in the pixel block unit.
Maximal value extracting unit 2 extracts the maximal value from the 2fi data in the pixel black unit, and outputs the value to level decision unit 4.
Minimal value extr;~cting unit 3 extracts the minimal value from the data in the pixel block unit, and outputs the value to level decision unit 4.
Level decision unit 4 determines the above-described levels 0 - 3 (LO - L3) based on the maximal and minimal value data, and outputs the determined levels.
Comparison units 5 ~- 8 each compare the pixel data output from data buffer 1 with levels LO - L3 input thereto. For example, comparison unit 5 inputs pixel data for pixel a shown in Fig. 1A, and compares the input data with LO - L3 to quantize the pixel data. Comparison unit 5 then outputs the quantized data to encoder 9.
Encoder 9 receives the maximal value output from maximal value extracting unit 2, the minimal value output from minimal value extracting unit 3, and quantiz~ed data (quan-a - quan-d) output from comparison units 5 - 8, and shapes the data into a prescribed format for output.
As explained above, according to the image data compressing device of the present embodiment;, maximal and minimal values and quantized data of pixel data are extracted and output. Thus, image data compression can be readily performed with such a simple configuration as described above.
Second Embodiment Fig. 3 is a block diagram showing a schematic configuration of an image data decompressing device according to the second embodiment of the present invention. The image data decompressing device includes: a decoder 11 that inputs compressed image data, and separates and outputs maximal value data, minimal value data and quantized data quan-a -quan-d of pixel data; a level decision unit 12 that determines quantization levels (level 0 - level 3) based on the maximal and minimal value data separated by decodE~r 11; select units 13 - 16 that select the quantization levels output from level decision unit 12 based on quantization data quan-a - quan-d output from decoder 11, to output as respective pixel data (Db -Dd); and an output unit 17 that outputs pixel data.
Decoder 11 inputs the compressed image data shown in Fig. 1C, and separates the maximal value data, the minimal value data and the quantized data quan-a - quan-d for each pixel data. For example, when the R values as shown in F:ig. 1C are input, maximal value Rmax, minimal value Rmin and Rquan (R,quan-a - Rquan-d) are separated. Decoder 11 then outputs maxiirial value Rmax and minimal value Rmin to level 3C1 decision unit 12, and outputs quantized data li,quan-a - Rquan-d to select units 13 - 16, respectively.
Level decision unit 12 determines and outputs the above-described levels 0 - 3 (LOD - L3D) based on the maximal and minimal values. Select units 13 - 16 select and output pixel data (restored data) that correspond to quantized data quan-a - quan-d. For example, if select unit 13 receives quantized data Rquan-a for the R value of pixel a, it outputs data value Da corresponding to the quantized data Rquan-a to output unit 17. Output .5 unit 17 receives, from seleca units 13 -16, data values Da - Dd corresponding to qmantized~ data Rquan-a - Rquan-d, and outputs them as pixel data. This p~cocess i:> sequentially performed for the G value, B value and a, value, so than the R, G, B and a, values of each pixel can be restored.
In the above-described embodiments, RGB and a values have been 11) compressed/decompressed. However, other data can be compressed in the same manner. For example, in the case where a Z buffer method is used for hidden-sunace removal in three dimensional gzaphics, maximal and minimal Z values ~r~ay be extracted so that the Z values of pixels can be quantized for compression.
15 As explained above, according to the image data decompressing device of the present embodiment, maximal and minimal value data as well as quantized data of pixel data are separated from compressed image data, and the pixel data are restored based on these data. Therefore, image data restoration can be readily performed with a simple configuration as 21) described above.
Third Embodiment Fig. 4 is a block diagram showing,a schematic configuration of an image display device including a three dimensional graphics accelerator according to the third embodiment of the present invention. The image 2;i display device includes: a central processing unit (CPU) 2 that peuorms overall control of the image display device; a main memory 22; a graphics accelerator 23; a control circuit 24 that controls generation of a timing signal for main memory 22 and graphics accelerator 23 and data input/output; an image memory 25 used for expansion of the image data;
31) and a cathode ray tube (CI~'"T) 2G on which an image is displayed.
Further, graphics accelerator 23 includes: a renderer 31 that generates image data by performing calculation of shape and color (hidden-surface processing, color tome calculation) of an object to be displayed on a _7_ screen based on a va.x-iety of models including a motion model; an image data compressing unit 32 that compresses the image data based on the shape and color of the objecit calculated by renderer 31; a memory controller 33 that wxltes the inxage data compressed by image data compressing unit 32 into image memory 25 and reads the compressed image data out of image memory 25; a:n image data decompressing unit 34 that restores original image data :from the compressed image data read out of image memory 25; a rastex:izer 35 vthat converts the image data output from image data decompressing unit 34 into a display format suitable for CRT 26; and a digital/analog converter (I)AC) 3G that converts digital signals output from rasterizer 35 to~ analog' signals. As processing by renderer 31 and rastex~izer 35 are well known and are not directly related to the present invention, they are not described in detail herE~.
For image data compressing unit 32 and image data decompressing unit 34, the image data compressing device and the image data decompressing device descx7ibed in the first and second embodiments are used. Thus, by applying the image data compressing device and the image data decompressing device i~o the graphics accelerator, the data amount required to represent the irr~age data, and hence, the capacity of image memory 25, can be reduced. Though an image display device with a three dimensional graphics accelerator has been described by way of example in the present embodiment, the present invention can be applied to other devices displaying images on other types of display screens.
Although the present invention has been described and illustrated in detail, it is clearly understood that the same is by way of illustration and example only and is not to be taken by way of limitation, the spirit and scope of the present invention being limited only by the terms of the appended claims.
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Claims (13)
1. An image data compressing device, comprising:
an extracting unit extracting two reference values from pixel values in a prescribed region of image data; and a quantization unit quantizing the pixel values in said prescribed region based on the two reference values extracted by said extracting unit.
an extracting unit extracting two reference values from pixel values in a prescribed region of image data; and a quantization unit quantizing the pixel values in said prescribed region based on the two reference values extracted by said extracting unit.
2. The image data compressing device according to claim 1, wherein said extracting unit includes a maximal value extracting unit extracting a maximal value from the pixel values in said prescribed region, and a minimal value extracting unit extracting a minimal value from the pixel values in said prescribed region.
3. The image data compressing device according to claim 2, wherein said quantization unit includes a level decision unit dividing a difference between the minimal value extracted by said minimal value extracting unit and the maximal value extracted by said maximal value extracting unit into a plurality of values, and a comparison unit comparing the pixel values in said prescribed region with the plurality values divided by said level decision unit.
4. The image data compressing device according to any one of claims 1 to 3, further comprising a data buffer temporarily retaining image data and outputting said image data to said extracting unit and said quantization unit.
5. An image data decompressing device, comprising:
an extracting unit extracting two reference values and quantized data of pixel values in a prescribed region from compressed image data; and a decompressing unit restoring the pixel values in said prescribed region based on the two reference values and the quantized data extracted by said extracting unit.
an extracting unit extracting two reference values and quantized data of pixel values in a prescribed region from compressed image data; and a decompressing unit restoring the pixel values in said prescribed region based on the two reference values and the quantized data extracted by said extracting unit.
6. The image data decompressing device according to claim 5, wherein said extracting unit includes a decoder extracting a maximal value, a minimal value and quantized data of the pixel values in the prescribed region from said compressed image data.
7. The image data decompressing device according to claim 6, wherein said decompressing unit includes a level decision unit dividing a difference between the minimal value and the maximal value extracted by said extracting unit into a plurality of values, and a select unit referring to said quantized data and selecting one of the plurality of values divided by said level decision unit.
8. An image display device, comprising:
an image data generating unit generating image data;
a first extracting unit extracting two reference values from pixel values in a prescribed region of the image data generated by said image data generating unit;
a quantization unit quantizing the pixel values in said prescribed region based on the two reference values extracted by said first extracting unit;
an image memory storing the two reference values extracted by said first extracting unit and the pixel values in t;he prescribed region quantized by said quantization unit as compressed image data;
a second extracting unit extracting two reference values and quantized data of pixel values in a prescribed region from the compressed image data stored in said image memory;
a decompressing unit restoring the pixel values in said prescribed region based on the two reference values and the quantized data extracted by said second extracting unit; and a display unit displaying on a display screen based on the pixel values in the prescribed region restored by said decompressing unit.
an image data generating unit generating image data;
a first extracting unit extracting two reference values from pixel values in a prescribed region of the image data generated by said image data generating unit;
a quantization unit quantizing the pixel values in said prescribed region based on the two reference values extracted by said first extracting unit;
an image memory storing the two reference values extracted by said first extracting unit and the pixel values in t;he prescribed region quantized by said quantization unit as compressed image data;
a second extracting unit extracting two reference values and quantized data of pixel values in a prescribed region from the compressed image data stored in said image memory;
a decompressing unit restoring the pixel values in said prescribed region based on the two reference values and the quantized data extracted by said second extracting unit; and a display unit displaying on a display screen based on the pixel values in the prescribed region restored by said decompressing unit.
9. The image display device according to claim 8, wherein said first extracting unit includes a maximal value extracting unit extracting a maximal value from the pixel values in said prescribed region, and a minimal value extracting unit extracting a minimal value from the pixel values in said prescribed region.
10. The image display device according to claim 9, wherein said quantization unit includes a level decision unit dividing a difference between the minimal pixel value extracted by said minimal value extracting unit and the maximal pixel value extracted by said maximal value extracting unit into a plurality of values, and a comparison unit comparing the pixel values in said prescribed region with the plurality of values divided by said level decision unit.
11. The image display device according to any one of claims 8 to 10, further comprising a data buffer temporarily retaining image data, and outputting said image data to said first extracting unit and said quantization unit.
12. The image display device according to any one of claims 8 to 11, wherein said second extracting unit includes a decoder extracting a maximal value, a minimal value and quantized data of the pixel values in the prescribed region from said compressed image data.
13. The image display device according to any one of claims 8 to 12, wherein said decompressing unit includes a level decision unit dividing a difference between the minimal value and the maximal value extracted by said second extracting unit into a plurality of values, and a select unit referring to said quantized data and selecting one of the plurality of values divided by said level decision unit.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP26362799A JP2001086500A (en) | 1999-09-17 | 1999-09-17 | Image data compressing device, image data extending device, device and method for displaying image using the same |
| JP11-263627 | 1999-09-17 |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2300326A1 CA2300326A1 (en) | 2001-03-17 |
| CA2300326C true CA2300326C (en) | 2003-02-18 |
Family
ID=17392152
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2300326 Expired - Fee Related CA2300326C (en) | 1999-09-17 | 2000-03-09 | Image data compression, decompression and display device |
Country Status (3)
| Country | Link |
|---|---|
| JP (1) | JP2001086500A (en) |
| CA (1) | CA2300326C (en) |
| DE (1) | DE10021819A1 (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105631905A (en) * | 2014-10-29 | 2016-06-01 | 新相微电子（开曼）有限公司 | Image compression algorithm and image compression control device for TFT-LCD driving IC |
-
1999
- 1999-09-17 JP JP26362799A patent/JP2001086500A/en not_active Withdrawn
-
2000
- 2000-03-09 CA CA 2300326 patent/CA2300326C/en not_active Expired - Fee Related
- 2000-05-04 DE DE2000121819 patent/DE10021819A1/en not_active Withdrawn
Also Published As
| Publication number | Publication date |
|---|---|
| CA2300326A1 (en) | 2001-03-17 |
| DE10021819A1 (en) | 2001-06-28 |
| JP2001086500A (en) | 2001-03-30 |
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