FR2631474A1 - CIRCUIT AND METHOD FOR CONTROLLING THE PRESENTATION OF COLOR INFORMATION TO A DISPLAY DEVICE OF A COMPUTER SYSTEM - Google Patents

Abstract

Such a circuit for controlling the presentation of color information to a display device comprising a plurality of picture element locations comprises first and second memories 101 having first and second sets of locations corresponding to said one. plurality of pixel locations and used to store pseudo-color information, and a third memory 103 having a third set of locations, each of which corresponds to a predetermined group of pixel locations and serving to control access to said first and second memory means 101, 102. Application in particular to computer systems carrying out the processing of color graphics.

Description

The present invention relates to the field of computer systems for

  processing of graphics and more specifically the field of control planes for controlling the presentation of pixel information of pixels to a display device. Typically, control plans in a graphics processing computer system permit presentation of the graphics color information to a display device. This display device consists of a number of picture elements that can be selected independently. The control plans provide color information for each of the pixel locations of the display device. In known systems, the control planes include a plurality of image buffers. Typically, two image buffers are provided. A first buffer may be used for registration of the display device, while a second buffer is modified by the computer system for subsequent display. It is known to provide such a technique of

  double buffering on a "screen-to-screen" basis.

  However, it is desirable to provide such a buffer in a computer, which allows the display of information windows. Such a computer system makes it possible, typically, to display a plurality of logically independent windows. In such a system, it would be useful to provide for a selection of a

  image buffer on a "window-to-window" basis.

  Known computer graphics processing systems allow the use of either pseudo-color codes or true color codes for. presenting color information to a display device. True color codes are used to present the red-green-blue (RGB) color information to a display device. The true color codes comprise three sets of bits, a first set of bits representing the intensity of the red color beam of the display device, a second set of bits representing the intensity of the green color beam of the display device and a third set of bits representing the intensity of the blue color beam of the display device. Typically, each of these bit sets can have eight bits for a total of

  24 bits of color information.

  Many known systems provide pseudo-color codes. Typically, the pseudo-color codes include a set of bits that are used as inputs to a color lookup table. The color look-up table outputs, as output signals, either a true color code or a real RGB color signal. The pseudo-color code typically has a smaller number of bits than is necessary for the true color codes, which saves the required memory space. In a large number of known systems, the number of bits used by a pseudo-color code is variable and, typically, this code may comprise eight, ten or twelve bits of information

concerning the colors.

  Although the use of pseudo-codes

  colors results in a saving of the required memory space, typically the use of true color codes provides better color rendition and a more accurate color. Therefore, in known computer graphics processing systems, the color mode can be switched from screen-to-screen mode to

  true color mode and pseudo-color mode.

  However, it is desirable to provide a switching between the color modes in a computer system, which allow the display of information windows and the display of a window using the true color mode and a second window using

the mode of the pseudo-colors.

  The present invention relates to the field of control planes used in computer graphics processing systems for controlling the presentation of color information to a display device. The present invention is particularly useful in a computer system using a plurality

  logical windows in its display device.

  The present invention makes it possible to provide a

  changing the color modes between a true color mode and a pseudo-color mode, which allows a first logical window to use the true color mode and a second logical window to use the pseudo-color mode . The computer system of the present invention utilizes a plurality of logic buffers for storing color information of the picture elements. A first buffer can be used to output color information to a display device, while a second buffer is updated with

  color information for subsequent display.

  The present invention is useful for enabling the selection of a buffer for display and, similarly, the selection of a buffer for updating, on a regular basis.

logical window by window.

  According to a first aspect, the present invention comprises a memory buffer comprising a first set of data bits, a second set of data bits and a third set of data bits, for each location of a picture element in a display device. The memory buffer further includes a plurality of control bits for controlling logical groups of picture elements in the display device. The control bits control whether data bits are interpreted as representing a color in the true color mode or in the pseudo-color mode. In addition, the control bits are used to control the one of the two buffers, which is used to obtain the color information for the display. According to this first aspect, the present invention allows a double buffering in the mode

pseudo-colors.

  In a second aspect, the present invention includes additional memory buffers for providing double buffering in true color mode.

  Other features and advantages of the pre-

  invention will emerge from the description given below.

  after reference is made to the accompanying drawings, in which: - Figure 1 shows a block diagram showing the memory buffers according to the present invention;

  - Figure 2 provides an illustration of a

  positive display which can be used in connection with the present invention;

  FIG. 3 represents an illustrative flowchart

  process according to the present invention; FIG. 4 is a block diagram of a color lookup table memory of the type that can be used in the present invention; and

  FIG. 5 represents a block diagram of a cir-

  cooked gamma correction of the type that can be used

in the present invention.

  A device and method for controlling the presentation of information about picture elements to a display device will be described. In the

  description that will follow, many specific details

  are mentioned, such as a number of bits, etc., so as to allow a detailed understanding of the present invention. However, it will be apparent to those skilled in the art that the present invention can be implemented without these specific details. In other cases, well-known circuits and structures have not been shown in detail so as not to obscure the present invention unnecessarily.

  The present invention is used in systems

  computer systems that support color display systems and, more specifically, computer systems that support color display devices and screen-cutting systems in windows. Typically, such computer systems allow the display of a number of windows, logically independent, of representations

  information on the same physical display device.

  In such a system, it is desirable to control the color information, on a window-by-window basis rather than on a screen-based basis. Many such computer systems provide either a true color mode or a pseudo-color mode. In a true-color mode, bits, representative of the color of the picture element, are stored for each picture element in the display device. In the preferred embodiment, the true-color mode uses 24-bit information, eight bits representing the intensity of the red-colored beam of the display device, eight bits representing the intensity of the green-colored and eight-bit beam. representing the intensity of the blue color beam. In a pseudo-color mode, a plurality of bits are used to represent the color of an image element of the display device and this plurality of bits is designated as an address for viewing corresponding bits, representing the intensity of the red, green and blue beams for this color. It is desirable to provide for a selection of either the true color mode or the pseudo-color mode for color representation on a display device in a computer system for assisting a system of cutting windows on a screen.

screen or windowing.

  Referring to FIG. 1, there are shown color memory buffers of the type that can be used in accordance with the present invention. The present invention includes a first memory pad 101 having three buffers 110, 111 and 112 for storing color information and a fourth buffer 113 for storing control information. In the preferred embodiment, each of the buffers 110, 111 and 112 has a plurality of eight-bit memory locations, each memory location corresponding to the location of an element.

  image on the display device.

  Referring briefly to Figure 2, there is shown a display device 201 of the type

  can be used in accordance with the present invention.

  The display device 201 may be any type of known frame scan display device, in which the display of the color information

  is accompanied by a command of the channels delivering the

  ceaux corresponding to the colors red, green and blue. The frame scan display device 201 comprises

  a plurality of picture elements, which may be

  independently, through the delivery channels

  beams of different colors.

  The picture elements on a display device

  ge 201 of the preferred embodiment are organized

  in groups, such as groups 202,203 and 204.

  In the preferred embodiment, each of the groups

  has a network of 20 pixel locations.

  The network of the preferred embodiment has a width of 5 pixels and a height of 4 pixels. In the preferred embodiment, the control buffer 113 of Fig. 1 has four bits corresponding to each of these picture element arrays. One of these bits indicates whether the grouping of picture elements operates according to the true color mode or the pseudo-color mode. Two of the bits are used to determine the buffer to be used to obtain the color information for the pixel locations of the element group

  when the system uses double buffering.

  The fourth bit is not used in the form of

preferred embodiment.

  Control of logical groups of picture elements makes it possible to obtain, in an efficient manner, in the context of the operation of the present invention, independent control of each individual location of a picture element. It is obvious to those skilled in the art that the present invention can be used with control bits for each individual location of a picture element or with a network having different dimensions without departing from the scope of the present invention. A reduced number of bits in a group of picture elements leads to increased requirements in terms of memory and processing, while allowing

better color control.

  When operating in pseudo-mode

  the present embodiment uses color information, including eight bits for each

  location of an image element of the display device.

  Referring to FIG. 4, it can be seen that the eight bits of the pseudo-color information 401 are used as address inputs in a memory array 402. The memory array 402 includes Logically speaking, 256 addressable memory locations each comprising 24 bits, usually referred to as color lookup tables. The particular memory can consist of 256 x 8 memories by an equivalent. Eight bits of information represent the intensity of the red color beam on the display device, eight bits of information represent the intensity of the green color beam and eight bits

  represent the intensity of the blue color beam.

  The data output signal 403 of the memory 402 is formed by the red, green, and blue color information, which corresponds to the pBeudo-color 401 used as the input address. This information of the red-green-blue (RGB) colors, delivered by the data output, can be used to control the color in the

display device.

  Referring again to FIG. 1, in the preferred embodiment, the pseudo-color mode uses two of the color data buffers, namely the data buffers 110 and 111. The data buffer used at a given instant particular is determined by the control information stored in the control buffer 113 for the group of picture elements containing a particular picture element. The data buffer 110 or 111 not currently used for presenting color information to the display device can

  be updated with new color information.

  The double buffering command is realized from this

  way for each individual group of picture elements.

  In the case of operation in the true color mode, the memory buffers 110, 111 and 112 can be used to store respectively

  Information about the color red, green and blue.

  Each of these memory buffers can store eight bits of color information for each picture element of the display device. The control information stored in buffer 113 indicates whether memory buffers 110, 111, and 112 are used for a particular group of picture elements for storing true color information or pseudo-color information. . Referring to FIG. 5, it can be seen that the red, green, and blue color information from the memory buffers 110, 111, and 112 of FIG. 1 are used as data input signals in the lines 501, 502 and 503. The circuit of FIG. 5 is used in the computer system of the preferred embodiment to perform color gamma correction. For example, the eight bits of the color information representing the intensity of the red color of the display device, obtained for the memory buffer 110 for a particular memory location, is used as the address input. in a 256 x 8 511 memory array. The contents of the memory array 511 are set for a particular operating environment, and for this purpose factors such as illumination, the particular display device used may be taken into consideration. etc. The data output signal 521 of the memory array 511 has eight bits of color information representative of the intensity of the red color beam of the display. A similar gamma correction is performed for the green bits by the use of the memory array 512 delivering, as output signal 522, eight bits of green color information, and a gamma correction for blue is performed using the memory array 513 having, as an output signal

  523, eight bits of blue color information.

  Referring again to FIG. 1, the preferred embodiment of the present invention comprises, in a second aspect, two additional memory chips, the memory chip 102 and the memory chip 103. These memory chips are used to perform double buffering of color information, when operating in true color mode. Each of these pads has two memory buffers, namely the memory buffers 120 and 121 in the memory board 102 and the memory buffers 130 and 131 in the memory board 103. Each of the memory buffers 120, 121, 130 and 131 has an eight bit memory location corresponding to each picture element on the display device. When a location of a picture element is selected according to the true color mode, the buffers 110 and 111 store the red color information, the stamps 120 and 121 store the green color information and the buffers 130 and 131 store information about the blue color. Buffers 110 and 111 may be designated red and red, respectively, buffers 120 and 121 may be designated green0 and green1, respectively, and buffers 130 and 131 may be designated blue and blue1. The control bits stored in control buffer 113 are used to determine whether to use color information stored in red 110, green buffer 120 and blue buffer 130 or color information stored in memory. in the red buffer 111, the green buffer 121 and the blue buffer 131. This is how the double

  true color information buffering.

  Although, in the preferred embodiment, separate memory boards 101, 102, and 103 are used for dual-buffering in true-color mode, it is obvious to the ordinary person that the present invention can be implemented using a single memory chip having two memories logically separated, a first logical memory for storing information of the colors red0, green0 and blue0 and a second logic memory for storing the color information

red1, green1 and blue1.

  Referring now to FIG. 3, a flowchart illustrating a method of the present invention is described. Starting at the left edge of each scan performed by the color beams of a display device, a pseudo-color buffer switch is set to zero, block 301. This tells the system that it should start displaying. color information according to the pseudo-color mode, at the left edge of each scan of the device. The control bit for controlling a selection is either pseudo-color mode or true color mode.s for the first group of picture elements and is then tested at block 302. If this control bit is a zero, the computer system assumes that the data bits for this group of picture elements are present according to the pseudo-color mode, branch 303. If the control bit is a 1, the computer system switches to True color, branch 304 and block 305. For each new group of picture elements in the scan line, branch 306, the control bit is tested. The control bit acts in the manner of a toggle switch, which toggles between them the pseudo-color mode and the true color mode. The mode is toggled over when the control bit is a "1" and remains in the existing mode if the control bit is a 0. At the beginning of each new line, branch 307, the system initializes the toggle switch ( pseudo-color buffer switch) in the mode of

pseudo-colors, block 301.

  A similar method is used to determine the buffer that is used to obtain information from

  colors in the case of the use of double buffering.

  As previously described, two bits of control information are used to control which one of the buffers embodies the present invention. A multiplexer is used to select between the two control bits. This allows the computer system to change one of the two control bits when updating the color information without performing the display. In the preferred embodiment, it is not necessary to have two bits of control information to control the selection of the

  True color mode compared to pseudo-mode

  colors, since the switching between these two modes is performed at speeds lower than those of

  variations occurring in the buffer used.

Claims (26)

  1. Circuit to control the presentation of a   information about colors to a display device   chage (201) in a computer system, said display device having a plurality of pixel locations, characterized in that said circuit comprises: first memory means (101) having a first set of locations memory corresponding to said plurality of pixel locations, each of which locations is used for storing pseudocolor information; second memory means (102) having a second set of memory locations corresponding to said plurality of pixel locations, each of which locations for storing pseudo-color information; third memory means (103) having a third set of memory locations, each of which corresponds to a predetermined group (202, 203, 204) of picture element locations, said third set of memory locations for controlling a plurality of memory locations; 'access   said first and second memory means (101, 102).   The circuit of claim 1, characterized in that each memory location forming part of said third set of memory locations comprises a bit of information.   3. Circuit according to claim 2, characterized in that each memory location of said first set of memory locations comprises eight information bits. 4. Circuit according to Claim 3, characterized   in that each memory location of said second set   memory slots has eight bits of information. tion.   5. Circuit according to claim 4, characterized in that it further comprises a table of consultation of   colors, used to convert pseudo-information   colors in a RGB color information.   The circuit of claim 5, characterized in that said predetermined group (202, 203, 204) of pixel locations comprises a network   pixel locations.   The circuit of claim 6, characterized in that said pixel element array has twenty pixel elements with five pixel elements.   width and height equal to four picture elements.   A circuit for controlling the presentation of color information to a display device (201) in a computer system, said display device comprising a plurality of pixel locations, characterized in that said circuit comprises: first memory means (101) having a first set of memory locations corresponding to said plurality of pixel locations, each of which locations is used for storing true color information; second memory means (102) having a second set of memory locations corresponding to said plurality of pixel locations, each of which locations for storing true color information; third memory means (103) having a third set of memory locations each of which corresponds to a predetermined group (202,203,204) of pixel locations, said third set   storage locations to control access to   said first and second memory means (101, 102).   The circuit of claim 8, characterized in that each memory location forming part of said first set of memory locations comprises eight bits of information.   - 5 The circuit of claim 9, characterized in that each memory location forming part of said second set of memory locations comprises eight bits of information.   Circuit according to claim 10, characterized   in that it further comprises a color look-up table, which serves to convert information from   pseudo-colors in RGB color information.   Circuit according to claim 11, characterized   in that said predetermined group (202,203,204) of pixel locations comprises a network   pixel locations.   Circuit according to claim 12, characterized   in that said array of picture element locations has twenty picture elements with five picture elements in   width and a height equal to four. picture elements.   14. Circuit according to claim 1, characterized   in that each memory location of said third set of memory locations comprises two bits of information. A method for controlling the presentation of color information to a display device (201) located in a computer system and comprising a plurality of picture elements, which are organized according to a plurality of logical groups, said color information comprising a plurality of information bits corresponding to each picture element of said plurality of picture elements, and said computer system further comprising a plurality of control information for selecting between modes color scheme for said color information, which corresponds to said logical group of picture elements, characterized in that it includes the steps of, for each group of picture elements, to: (a) examine said picture information; a command corresponding to said group of picture elements for selecting said color mode; and (b) presenting the red-green-blue (RGB) signals to said display device (201) for each picture element in said group of picture elements, said RGB signals being produced on the basis of said color information, corresponding to said image element, and said corresponding control information said group of picture elements.   A method for controlling the presentation of color information to a display device (201) located in a computer system and comprising a plurality of image elements organized according to a plurality of logical groups of elements image (202,203,204), said color information comprising a plurality of information bits corresponding to each of   said plurality of picture elements representing the information   red-green-blue (RGB) color scheme in the true-color mode or in the pseudo-color mode, and said computer system further comprising control information consisting of a plurality of bits and serving to establish a selection between color modes, each bit of said plurality of bits of control information corresponding to one of said logical groups of picture elements, characterized in that it includes the steps of, for each scan line on said display device, to: (a) position a toggle switch to select a first color mode; and (b) for each logical group (202,203,204) of picture elements: (1) examining said bit of the control information corresponding to said group of picture elements and flipping said rocker lever in the case where said bit of the control information is in a first binary state; and (2) sending red-green-blue (RGB) signals to said display device for each picture element located in said group of picture elements, said   signals (RGB) being produced on the basis of the said information   color matching corresponding to said image element, and   of said control information corresponding to said group pe elements of image.   17. The method according to claim 16, characterized   in that said color information comprises eight bits of information in the pseudo-color mode and 24   bits of information in true color mode.   18. The method of claim 16, wherein   which said first color mode is a pseudo mode colors.   19. The method of claim 16, characterized   in that said first binary state is a high binary state. A circuit for controlling the presentation of color-related information to a display device (201) in a computer system, said display device comprising a plurality of pixel locations, said locations picture elements being organized into a plurality of logical groups (202, 203, 204), characterized in that said circuit comprises first memory means (101) having a first set (110) of memory locations corresponding to said plurality of memory groups; pixel locations for storing information about a color, a second set (111) of memory locations corresponding to said pixel locations for storing information about a color image, color, a third set (112) of memory locations corresponding to said plurality of picture element locations for storing information about a stream ur and one. fourth set (113) of memory locations corresponding to said plurality of logical groups of memory element locations for storage a command information.   21. Circuit according to claim 20, characterized   further comprising second memory means (102) having a fifth set (120) of memory locations corresponding to said plurality of pixel locations for storing memory true color information.   22. Circuit according to claim 21, characterized   in that it also includes third means of   memory (103) having a seventh set (130) of memory element locations corresponding to said plurality of picture element locations for the   memorizing information of true colors.   23. Circuit according to claim 22, characterized   wherein said second memory means (102) further comprises a sixth set (121) of memory locations corresponding to said plurality of pixel locations for storage   True color information.   24. Circuit according to claim 23, characterized   wherein said third memory means (103) further comprises an eighth set (131) of memory locations corresponding to said plurality of pixel locations for storage   True color information.   25. Circuit according to claim 24, characterized   in that it further comprises a color look-up table for converting pseudo-color information into information of red-green-blue (RGB) colors.   26. Circuit according to claim 25, characterized   in that it comprises a gamma correction circuit for receiving true color information and for   produce RGB color information.