JP3969436B2 - Color palette management apparatus and method, program - Google Patents

Description

  The present invention relates to a color palette management apparatus that is used in an image display system of a color palette system and rewrites the contents of a color palette.

  As a color expression method in an image display system, there are a direct color method and a color palette method. The direct color method directly specifies the color component value of each pixel in the image. For example, in the RGB (red, green, blue) color space, the red intensity level and the green intensity level for each pixel in the image. A color image is represented by designating each of the blue intensity levels. For example, if 8 bits are assigned per color, 24 bits per pixel are required. On the other hand, the color palette method represents an image using a smaller color set, and in many cases includes 256 (2 8) different colors. In this case, each pixel in the color image can be represented not by 24-bit color information but by an 8-bit index of the color palette, and the data amount can be reduced to one third.

  An outline of a color palette type image display system will be described with reference to FIG. The image data drawn by the drawing processing block 101 is written into the memory 103 by the memory control block 102. Then, the memory control block 102 reads image data necessary for display from the memory 103 and sends it to the display processing block 104. The image data is represented by a color palette method, and the display processing block 104 obtains color information corresponding to an index (color address) set for each pixel with reference to the color palette 105. Then, display is performed using this color information.

  In the case of the color palette method, there is an effect of reducing the data amount as described above, but there is a demerit that the expressive power is limited because the number of colors to be used is limited. Here, if an attempt is made to increase the number of colors using the color pallet, it is necessary to increase the number of color pallets, which increases the amount of memory used. The color palette is usually composed of a memory such as SRAM. For example, 1024 colors can be prepared at one time by using four color palettes each including 256 different colors. .

  As described above, since the number of colors is limited when the color palette method is adopted, a technical idea of rewriting the color palette can be considered as a natural flow. In this way, the number of usable colors per frame can be increased without increasing the memory usage as much as possible. However, the color palette is composed of a memory such as SRAM, and rewriting takes time.

  Accordingly, it is an object of the present invention to provide a color palette management apparatus and the like that do not require rewriting the contents of the color palette.

The color palette management device according to claim 1 is an example for realizing the color palette management method according to claim 5 , and the color information for displaying an image is different from the color information stored in the color palette. Difference information, which is information of only the part, is stored in the difference information storage means. Then, when displaying the image, control is performed so as to refer to the color palette when there is no difference information and to refer to the difference information storage means when there is difference information. In this way, since the color palette itself does not need to be rewritten, it is not necessary to consider the time required for rewriting. The difference information may be stored in the header portion of the image data as shown in claim 2 or may be calculated by the difference information calculation means as shown in claim 3.

Further, as shown in claim 4, when the function as the color palette management device according to any one of claims 1 to 3 is realized in a computer system, for example, it may be provided as a program to be started on the computer system side. it can. In the case of such a program, for example, the program is recorded on a computer-readable recording medium such as a flexible disk, a magneto-optical disk, a CD-ROM, a hard disk, a ROM, or a RAM, and is loaded into a computer system and started as necessary. It can also be used by loading and starting over a network.

  Embodiments to which the present invention is applied will be described below with reference to the drawings. Needless to say, the embodiments of the present invention are not limited to the following embodiments and can take various forms as long as they belong to the technical scope of the present invention.

[First Embodiment]
FIG. 1 shows a schematic configuration of the image display system according to the first embodiment. The image display system of this embodiment includes a drawing processing block 11, a memory control block 12, a memory 13, a display processing block 14, a color palette 15, a color palette control unit 16, and a palette management table 17.

  The drawing processing block 11 draws color pallet image data in accordance with a command input from a control unit (not shown). The memory control block 12 writes the image data drawn by the drawing processing block 11 into the memory 13. The memory 13 is composed of a VRAM or the like. When displaying the image data on the memory 13, the memory control block 12 reads out the image data necessary for display from the memory 13 in the raster direction, and the color corresponding to the address value of the color palette set for each pixel. Information (for example, RGB values) is obtained by referring to the color palette 15 and RGB conversion is performed. And it outputs with a suitable timing with respect to the indicator which is not shown in figure via a D / A converter. For example, a liquid crystal display, a plasma display, a CRT, or an organic EL can be used as the display.

  Here, the contents of the color palette 15 are not fixed, and the color palette controller 16 rewrites the color palette according to the information in the palette management table 17. FIG. 1B shows an example of the palette management table 17. In the palette management table 17, the coordinates of the start and end points of the area in the frame and the type of palette to be used are entered. When displaying the area written in the palette management table 17, the color palette 15 is rewritten. As shown in FIG. 1C, in this embodiment, it is assumed that color palette information is arranged in the header portion of the image data.

  Since the color palette 15 is composed of a memory such as an SRAM and the like, it takes time to rewrite the memory. Therefore, in order to match this palette rewriting with the display, the palette rewriting is prepared from a predetermined time before the display start. The color palette control unit 16 has a function of generating the timing for starting the color palette rewriting, and the “predetermined time” is a time during which the rewriting of the color palette 15 can be completed, for example. Since the rewriting can be completed, for example, it may be a “time that is just in time” such that the processing for display starts immediately after the rewriting is completed, or “a time for completing the rewriting with a margin” It may be.

  Here, a specific example of the color palette control method will be described. The control of the color palette basically employs the uppermost surface (layer) when a plurality of screens are combined to generate a display image. In the case where they do not overlap, the planar positional relationship between layers is considered. At this time, since the image data is read in the raster direction, the positional relationship between the layers in the screen vertical direction (Y direction) is particularly taken into consideration.

  (1) For example, in the example shown in FIG. 2A, layers L2 and L3 of relatively small areas are included in layer L1 of a relatively large area, and layers L2 and L3 are in the Y direction. This is a case where they do not overlap. In this case, the display order of the layers L2 and L3 is such that the display of the layer L3 starts after the display of the entire layer L2 is completed. If the display of the layer L2 is completed, the color information for the layer L3 is rewritten. That is, one color palette is assigned to the layer L1, and the other color palette is assigned to the layer L2 first and then to the layer L3 in order. In this way, for example, only two color palettes are prepared, and even a screen display including three layers L1, L2, and L3 each having a unique color usage can be handled. In other words, considering the number of colors used in the entire screen, even if three color palettes are required, the contents of the color palette can be changed appropriately as described above, taking into account the relationship between the areas in one screen. By rewriting, two color palettes are enough.

  (2) On the other hand, in the example shown in FIG. 2B, the layers L2 and L3 of a relatively small area overlap the layer L1 of a relatively large area, and the layers L2 and L3 overlap in the Y direction. It is. In this case, one color palette is assigned to the layer L1 in the same manner as in FIG. 2A. However, for the other color palette, the layers L2 and L3 are assigned in order. Can not. Therefore, for the portion where the layers L2 and L3 overlap in the Y direction, the contents of the color palette are rewritten for the layer L3 until the display of the layer L3 is started after the display processing of the layer L2 is completed, and the display of the layer L3 is performed. When the processing is completed, the rewrite control of rewriting the contents of the color palette for the layer L2 is repeated until the display of the layer L2 is started. In this way, the display of the screen including three layers L1, L2, and L3 each having a unique color usage can be handled with two color palettes.

  (3) Moreover, the example shown to Fig.3 (a) is a case where a part of layer L3 has overlapped with a part of layer L2. In this case, before and after the portion where the layer L3 overlaps the layer L2, when viewed in the raster direction, the layer L2 → the layer L3 → the layer L2. Therefore, the color palette for layer L2 cannot be rewritten for layer L3. Therefore, in the part where both layers L2 and L3 overlap, it is necessary to allocate one color palette for layer L2 and the other color palette for layer L3. For this reason, the type of color palette corresponding to the area is as shown in FIG. That is, the type a color palette is used in the area of the start point (X0, Y0) and the end point (X1, Y1) (see FIG. 3A), and this is assigned to the palette A in the color palette 15. In the area of the start point (X0, Y1) and the end point (X1, Y2), the type a color palette and the type b color palette are used. Since the color palette of type a is assigned to palette A, the color palette of type b is assigned to palette B. In the area of the start point (X2, Y2) and the end point (X3, Y3), the type b color palette is used. A color palette of type c is used for the layer L4 that does not overlap with the layers L2 and L3 in the Y direction. This type c color palette can be dealt with by rewriting the contents of palette A. Also in this case, it is possible to cope with the display of the screen including the three layers L2, L3, and L4 each having a unique color usage by preparing only the A and B color palettes.

  Note that the positional relationship between a plurality of layers included in one screen as shown in (1) and (2) described above is known at the time of image data creation. Therefore, the palette management table 17 corresponding to the image data can be prepared in advance. However, as shown in (3), when a screen is synthesized using a plurality of image data read from the memory 13, a necessary color changes depending on how the images are synthesized. That is, the necessary color information is that of the layer that is synthesized on top. Therefore, when such layer composition is also supported, a management table creation unit 18 is provided as shown by a broken line in FIG. 1A, and the management table is based on synthesis information from a control unit (not shown). Was created. As a result, processing can be performed with minimal palette rewriting.

  As described above, the color palette control unit 16 rewrites the color palette 15 according to the information in the palette management table 17 indicating the correspondence between the area in one screen and the color palette type to be used. The color information necessary at that time can be appropriately rewritten. As a result, if the number of color palettes 15, that is, the color palette is composed of SRAM, the number of usable colors per frame can be increased without increasing the amount of SRAM used.

[Second Embodiment]
FIG. 4A shows a schematic configuration of the image display system according to the second embodiment. The same components as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  The system according to the second embodiment includes a color information comparison unit 21 in addition to the drawing processing block 11, the memory control block 12, the memory 13, the display processing block 14, the color palette 15, and the color palette control unit 16. The color information comparison unit 21 compares the color information stored in the color palette 15 with the color information corresponding to the image data of the area to be used next after rewriting the color palette 15. Then, based on the comparison result, the color palette control unit 16 rewrites only the color information of the difference portion in the color palette 15. For example, color information common to the layers L2 and L3 in FIG. 2 described above may be used. Even if the layers L2 and L3 have their own unique colors, they do not mean that there is no common color at all. In fact, it seems that there are actually some common colors. In such a case, it is not necessary to update all the color information in the color palette 15, and the processing amount can be reduced by updating only the portions that are different between the color information used in the layer L2 and the color information used in the layer L3. Can do.

  When the color information of the color palette 15 is rewritten only in such a difference portion, the reference color palette information is read from the memory 13 via the memory control block 12 in order to restore the rewritten portion. As a result, the processing time for rewriting becomes long. Therefore, a configuration in which a save buffer 22 is added as shown in FIG. In this case, the color palette information before rewriting is temporarily stored in the save buffer 22 and then rewriting is executed. When the rewritten color palette area is used, the color palette information temporarily stored in the save buffer 22 is returned to the color palette 15. In this way, it is possible to quickly return to the reference color palette 15 with a small amount of processing.

  In the example illustrated in FIG. 2B described above, the layers L2 and L3 overlap in the Y direction. In this case, as shown in FIG. 2B, the time allowed for rewriting from the color palette information for the layer L2 to the color palette information for the layer L3 is shorter than when the layers do not overlap in the Y direction. Therefore, a device for shortening the time required for such rewriting processing is particularly effective in such a situation that rewriting in such a short period is required.

[Third Embodiment]
FIG. 5A shows a schematic configuration of the image display system according to the third embodiment. The same components as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted. The system of the third embodiment includes a reference palette switching unit 31 and a difference data buffer 32 in addition to the drawing processing block 11, the memory control block 12, the memory 13, the display processing block 14, and the color palette 15. As shown in FIG. 5B, difference data that is data of only a portion different from the contents of the color palette 15 is arranged in the header portion of the image data in the present embodiment. For example, if the color palette used in the layer L2 shown in FIG. 2 is the reference color palette, only the color information of the portion different from the reference color palette is included in the header portion as difference data in the image data for the layer L3. It is arranged. Then, the difference data read from the header part is stored in the difference data buffer 32. The difference data buffer 32 corresponds to “difference information storage means” in the claims.

  In the case of this embodiment, the color palette control unit 16 as in the first or second embodiment is not provided, and the reference palette switching unit 31 only switches the reference destination. Specifically, switching control is performed as follows. That is, the color palette 15 is referred to when displaying the layer L2. On the other hand, when displaying the layer L3, the difference data buffer 32 is first referred to, and if there is no corresponding data, the color palette 15 is referred to next.

  In this way, it is not necessary to rewrite the stored contents of the SRAM, which is the color palette 15, and therefore it is not necessary to consider the time required for rewriting. Therefore, as in the second embodiment, as shown in FIG. 2B, it is effective in a situation where switching of color palette information to be used occurs in a short time.

  In the case of the configuration shown in FIG. 5A, as shown in FIG. 5B, data different from the reference color palette needs to be included in the image data in advance as difference data. Therefore, if it is applied to normal image data, the configuration shown in FIG. The configuration illustrated in FIG. 6A has a content in which a difference information calculation unit 33 is added to the configuration illustrated in FIG. In this case, for example, if the color palette used in the layer L2 shown in FIG. 2 is a reference color palette, the color palette information used in the image data for the layer L3 is all arranged in the header portion. . Then, the difference information calculation unit 33 compares the color information for the layer L2 stored in the color palette 15 with the color information for the layer L2 read from the header part of the image data of the layer L3, and calculates the difference. . The difference data calculated in this way is stored in the difference data buffer 32. The other operations are the same as those in the configuration of FIG. The difference information calculation unit 33 corresponds to “difference information calculation means” in the claims.

[Fourth Embodiment]
FIG. 6B shows a schematic configuration of the image display system according to the fourth embodiment. The same components as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted. The system of the fourth embodiment includes a differential data buffer 41 and an RGB correction unit 42 in addition to the drawing processing block 11, the memory control block 12, the memory 13, the display processing block 14, and the color palette 15.

  The RGB value correction unit 42 corrects the RGB values as color information extracted from the color palette 15 and outputs the corrected values to the display processing block 14. In the present embodiment, the RGB values are corrected. This is an example of a process of “processing color information stored in the color palette 15”, and therefore the RGB value correcting unit 42 is claimed in the claims. Corresponds to “color information processing means”. Such color information processing is performed for the purpose of, for example, generating a gradation in the background color so as to appear hazy as the distance increases, in order to express perspective for map image data, for example.

  Similarly to the case of the third embodiment, the difference data of the color palette is also arranged in the header portion of the image data in this embodiment, and the difference data read from this header portion is the difference data buffer 41. Stored in The difference data buffer 41 corresponds to “processing information storage means” in the claims.

  The RGB value correcting unit 42 uses the color information stored in the color palette 15 as it is when there is no difference data, and performs RGB conversion based on the color information stored in the color palette 15 when there is difference data. After that, correction according to the difference data is performed. Also in this embodiment, since the contents of the color palette 15 are not changed at all, effects such as speeding up of processing and simplification of control can be obtained.

[Others]
Since the screen illustrated in FIG. 2 includes layers L2 and L3 in the background layer L1, one color palette is assigned to the layer L1, and the other color palette is initially a layer. Allocation is performed in order for L2 and then for layer L3. Therefore, two color palettes are necessary. However, for example, when there is no background layer L1 and the screen is composed of only layers L2 and L3, one color palette can be used. Of course, there are cases where three or more color palettes are used, but the point is that a smaller number of color palettes can be used than when preparing a color palette corresponding to the number of colors used in the entire screen. There is an effect of becoming.

(A) is a schematic block diagram of the image display system of 1st Embodiment, (b) is explanatory drawing of a pallet management table, (c) is explanatory drawing of image data. It is explanatory drawing which illustrates the relationship between the layers in 1 screen. (A) is explanatory drawing when layers overlap in one screen, (b) is explanatory drawing of the pallet management table in the case of (a). It is a schematic block diagram of the image display system of 2nd Embodiment. It is a schematic block diagram of the image display system of 3rd Embodiment. (A) is a schematic block diagram which shows another aspect of the image display system of 3rd Embodiment, (b) is a schematic block diagram of the image display system of 4th Embodiment. It is a schematic block diagram of the conventional image display system.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Drawing processing block, 12 ... Memory control block, 13 ... Memory, 14 ... Display processing block, 15 ... Color palette, 16 ... Color palette control part, 17 ... Pallet management table, 21 ... Color information comparison part, 22 ... Saving Buffer 31. Reference palette switching section 32. Difference data buffer 33. Difference information calculation section 41. Difference data buffer 42. RGB correction section

Claims (5)

Used in color pallet image display systems,
A color palette for storing reference color information;
For color information for displaying an image, difference information storage means for storing difference information that is only information different from the color information stored in the color palette;
When displaying the image, there is provided a reference palette switching unit that controls to refer to the color palette when there is no difference information and to refer to the difference information storage unit when there is the difference information. A featured color palette management device. The color pallet management apparatus according to claim 1,
The color pallet management apparatus, wherein the difference information is stored in a header portion of image data. The color pallet management apparatus according to claim 1,
Difference information calculation means for calculating the difference information by comparing color information set corresponding to image data and color information stored in the color palette;
The color pallet management apparatus characterized in that the difference information calculated by the difference information calculation means is stored in the difference information storage means. The program for making a computer implement | achieve the function as a color palette management apparatus in any one of Claims 1-3. A color palette management method in a color palette type image display system,
  For color information for displaying an image, difference information that is only information that is different from the color information stored in a color palette that stores reference color information is stored. Control to refer to the color palette when there is no difference information and to refer to the difference information when there is difference information.
  Color pallet management method characterized by

Images