Computer graphics processing and selective visual display system – Computer graphic processing system – Plural graphics processors
Reexamination Certificate
1997-12-22
2004-01-13
Jankus, Almis R. (Department: 2671)
Computer graphics processing and selective visual display system
Computer graphic processing system
Plural graphics processors
Reexamination Certificate
active
06677950
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention is related to graphics computers that process images to draw graphics data such as characters and graphic elements, and image data processing systems or graphics computers that use such an image processor. Especially, this invention is related to an image data processing system that expands and processes binary data, including characters, symbols, etc. in a low-price and compact graphics computer, as well as to a memory configuration and control method to shorten the drawing time.
The graphics computer that stores character codes and graphic elements and draws, displays, or prints out graphics data on the basis of such character codes and graphic elements uses frame buffers to store the graphic data corresponding to pixels to be displayed on a screen (hereafter, to be referred to as pixel data).
When drawing graphics data, drawing processings and display processings are needed. The drawing processing includes computing pixel positions and pixel data itself from character codes and graphic elements and writing the pixel data in a frame buffer according to the pixel positions. The display processing includes repetitive and sequential reading of pixel data from the frame buffer corresponding to the pixels displayed on the screen synchronously with the raster scanning in the display device to display stable images on the screen.
In this section, the conventional technology related to display data will be explained first. In order to reduce the price of a graphics computer, a well-known method involves adopting a configuration in which a frame buffer is arranged in a large capacity main memory. Such a technique is disclosed as part of the graphics processing system described in Japanese Patent Laid-Open No. 84192/1992, and by the display architecture designed by Robert P. Colwell and described in “IEEE 1st International Conference on Computer Workstation”, (pp.30-37) (November, 1985), which is a scientific journal published in the United States. In those devices, a high access mode for a DRAM, etc. is used as a memory for the display, reducing the display processing load. In other words, the horizontal direction of the frame buffer is aligned with the direction of the column addresses in the DRAM, etc.
When drawing pixel data, however, accesses to addresses of different rows are often obtained in the frame buffer even for continuous pixels in the 2-dimensional coordinate system. For example, when drawing a line which is almost vertical, the access addresses are separated from each other by as much as the width of the frame buffer horizontal memory even when they are adjacent in the 2-dimensional coordinate system. At present, the main current of the display format for personal computers is 640 pixels in the horizontal direction by 480 pixels in the vertical direction, and one byte is assigned per pixel, but the number of bytes per pixel is changed now to 4 bytes. In other words, the horizontal memory width is 640 bytes or 2560 bytes. The column address width for a DRAM, etc. is 1 KB to 4 KB. Since both are almost the same in size, addresses of different rows are often accessed for the vertical two consecutive pixels. The high speed access mode is effective only for accessing addresses of the same row. The conventional technology may not be enough therefore to speed up the access satisfactorily for drawing. (1st conventional technology)
As for the line drawing method among drawing processings, a method to find an equation to represent a line between two points from two coordinate points and find a coordinate point between the two points using an equation is described on pages 443 to 446 in “Computer Graphics” (published in 1984) written by James D. Foly and Andries Van Dam, and translated by Atsumi Imamiya. (2nd conventional technology)
An embodiment of a high speed line drawing system is also described in Japanese Patent Laid-Open No. 200087/1982. (3rd conventional technology) According to this system, coordinates for drawing are found by reading the vector data represented by the increment of the Y coordinate when the X coordinate is increased by one. The vector data is expanded to dots beforehand and the result is stored in a vector data storage, and storing addresses are computed from the coordinates of start and end points. Another method is also described in Japanese Patent Laid-Open No. 200087/1982. According to this method, vector data is expanded to dots beforehand and then stored in the vector data storage, and storing addresses are computed from the coordinates of start and end points. The coordinates for drawing are then found by reading the vector data represented by the increment of the Y coordinate when the X coordinate is increased by one.
An embodiment of a character drawing system is described in “HD64410 ARTOP Users Manual” (pages 194 to 199) (4th conventional technology). The system draws pixel data in the frame buffer by expanding binary data, such as characters, to multivalue data.
In the above-referenced publication, expansion of binary data represented by “0” and “1” in the format of 16×16 bits, as shown in
FIG. 2
therein, to multivalue data is described. This binary data, for example, means character and symbol data (hereafter, to be referred to as character data). A set of such character data is stored in a character generator ROM (CGROM). A character code is assigned to each character and character data is accessed with those character codes.
Therefore, the addresses of the character data, corresponding to the character codes and stored in a memory, can be found by computing numerals according to the characteristics of the arrangement of characters. The correspondence of the character data to such memory addresses may be considered to be represented by a coordinate system comprising 16 pixels in the X direction and 16 pixels in the Y direction, and assuming the point that has row number 1 and column number 1 as the origin, as shown in FIG.
2
.
Expansion of binary data to multivalue data is performed by converting character data, represented by k binary data and the addresses of the character data in the CGROM, to multivalue (colored and multigraded) data and its addresses in the frame buffer.
The 5th conventional technology is a method for high speed drawing, which includes binary data mask processings. The method is described in Japanese Patent Laid-Open No. 135162/1993 “Image Processing System”.
This conventional technology is related to expansion of binary data to multivalue data and to using multi-colors for display. The method is a little different in handling color elements from the drawing technology mentioned here.
In other words, since RGB color elements are taken into account for display, one pixel comprises 3 elements and more data is handled. As a result, processings become more complex than those of the basic technology for multivalue expansion.
In this invention, however, the same concept as the multivalue expansion to be performed for drawing can be assumed by considering the technology as applied to one color element.
This invention is featured by using a RAM to store multivalue data corresponding to “1” in binary data. In this RAM is stored expanded data for plural pixels. With this, plural pixels can be processed concurrently to speed up the expansion processing.
The multivalue expansion processing is carried out by masking the multivalue data for the number of pixels stored in the RAM corresponding to “0” in binary data.
SUMMARY OF THE INVENTION
According to the 1st conventional technology, the access to the frame buffer is often for addresses of different rows in memory. And, the high speed memory access mode is allowed only within the addresses of the same row. Therefore, the access time may not be speeded up enough for drawing pixel data in the same conventional technology.
According to the 2nd conventional technology, no sufficient consideration is given to line length for drawing, and equations to compute coordinate points must be found regardless of the line length. The processin
Katsura Koyo
Minami Rika
Ohba Mamoru
Watabe Mitsuru
Antonelli Terry Stout & Kraus LLP
Hitachi , Ltd.
Jankus Almis R.
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