Decompressing and compositing graphical image data

• US 6,424,342 B1
• Filed: 09/16/1998
• Issued: 07/23/2002
• Est. Priority Date: 09/16/1998
• Status: Expired due to Fees

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: WebTV Networks Inc. (Microsoft Corporation)
• Inventors: Clough, Beth, Perlman, Stephen G.
• Primary Examiner(s): Zimmerman, Mark
• Assistant Examiner(s): Sealey, Lance W.
• Application Number:
  US09/154,181
• Time in Patent Office: 1,406 Days
• Field of Search: 345/418, 345/202, 345/555, 382/232, 382/233, 382/253, 348/393, 348/405, 348/437
• US Class Current: 345/418
• CPC Class Codes: G06T 11/40 Filling a planar surface by adding surface attributes, e.g. colour or texture
• CPC Class Codes: G06T 15/005 General purpose rendering architectures
• CPC Class Codes: G06T 15/04 Texture mapping

Abstract

Systems and methods for mapping, decompressing, and compositing graphical image in preparation for displaying an image on a display screen. Graphical image data is received by a graphics engine, which maps portions of the data to pixel positions on the display screen. If the data is compressed, it is decompressed after being mapped to pixel locations. The data is then composited in a scanline buffer, which stored display parameters that specify the colors and other properties of pixel in a single scanline on the display screen. Mapping the data prior to decompression reduces the random access memory resources otherwise required. In particular, the entire volume of compressed graphical image data received by the graphics engine does not need to be decompressed and stored in a random access memory device before being mapped to pixels on the display screen. In addition, the scanline buffers allow an entire frame on the display screen to be refreshed while storing, at any one instant, composited data corresponding to no more than two scanlines.

Claims

1. In a system that includes a graphics engine for rendering images on a display screen, a method for processing compressed graphical image data received by the graphics engine in preparation for rendering an image represented by the graphical image data, wherein less than all of the compressed graphical image data received by the graphics engine is decompressed, comprising the steps of:

receiving compressed graphical image data and information specifying a boundary encompassing graphical image data that is to be rendered on the display screen, wherein a first portion of the compressed graphical image data is positioned within the boundary and is to be rendered on a scanline of the display screen and wherein a second portion of the compressed graphical image data is positioned outside the boundary and is not to be rendered on the display screen;

mapping the first portion of the compressed graphical image data to pixels of a scanline of the display screen prior to the first portion of the compressed graphical image data being decompressed;

decompressing the first portion of the compressed graphical image data that has been mapped to the pixels of the scanline so as to identify display parameters to be assigned to the pixels and translucence parameters specifying a relative weight to be given to the display parameters with respect to any data previously stored at a scanline buffer associated with the scanline;

compositing the display parameters to the scanline buffer using the translucence parameters; and

transmitting the composited display parameters to the display screen to refresh the scanline as part of an operation of refreshing the display screen, wherein the display screen is refreshed without the second portion of the compressed graphical image data being decompressed.

2. A method as defined in claim 1, wherein the scanline buffer is capable of storing, at any one time, display parameters to be assigned to the pixels of no more than a single scanline.

3. A method as defined in claim 1, wherein the step of mapping the first portion of the compressed graphical image data comprises the step of identifying a segment of the scanline of the display screen on which the first portion of the compressed graphical image data is to be displayed.

4. A method as defined in claim 1, wherein the step of mapping the first portion of the compressed graphical image data comprises the step of identifying addresses associated with a memory device, the addresses being assigned to the first portion of the compressed graphical image data.

5. A method as defined in claim 4, wherein the step of decompressing the first portion of the compressed graphical image data comprises the step of retrieving the first portion of the compressed graphical image data from the memory device using the addresses.

6. A method as defined in claim 1, wherein the step of decompressing the first portion of the compressed graphical image comprises the step of performing vector quantization decompression on the first portion of the compressed graphical image data.

7. A method as defined in claim 6, wherein the first portion of the compressed graphical image data includes vector data structures, the step of performing vector quantization comprising the steps of:

reading one of the vector data structures; and

identifying an entry in a decompression codebook, the entry being referenced by said one of the vector data structures, the entry specifying the display parameters.

8. A method as defined in claim 1, wherein the step of compositing the display parameters comprises the step of combining the display parameters and other data already stored at the scanline buffer.

9. A method as defined in claim 8, wherein the step of combining the display parameters with the other data is conducted by combining the display parameters and the other data using a translucence parameter associated with the display parameters, the translucence parameter specifying a relative weight to be given to the display parameters with respect to the other data as the display parameters and the other data are combined.

10. A method as defined in claim 1, wherein:

the graphical image data resides in an image data coordinate system having a u axis and a v axis;

the boundary is trapezoidal and defines a pixel coordinate system having an x axis and a y axis that are not parallel with the u axis and the v axis, respectively; and

the step of mapping the first portion of the compressed graphical image data to pixels of a scanline comprises the step of mapping compressed graphical image data defined in the image data coordinate system to pixel coordinates of the pixel coordinate system.

11. A method as defined in claim 1, wherein the pixel coordinate system defined by the boundary is selected such that the first portion of the compressed graphical image data, when rendered by the graphics engine after the step of mapping, provides a perception of perspective.

12. In system including a display screen and a processor capable of transmitting signals to the display screen so as to display an image on the display screen, a method for processing graphical image data, comprising the steps of:

accessing, by a processor, compressed graphical image data structures;

accessing, by the processor, cel data structures, each being associated with one of the compressed graphical image data structures and defining a region of the display screen on which said one of the compressed graphical image data structures is to be represented;

determining which of the cel data structures define a region of the display screen that includes at least a segment of a selected scanline of the display screen;

for each of the cel data structures that define a region of the display screen that includes at least a segment of the selected scanline, repeating the steps of;

mapping a portion of the associated compressed graphical image data structure to pixels of the segment of the selected scanline;

decompressing the mapped portion so as to identify display parameters to be assigned to the pixels; and

compositing the display parameters to a scanline buffer associated with the selected scanline; and

transmitting the composited display parameters to the display screen.

13. A method as defined in claim 12, further comprising, when the step of transmitting the composited display parameters to the display screen has been initiated, the step of compositing, to a second scanline buffer associated with a second scanline, second display parameters to be assigned to pixels of the second scanline.

14. A computer program product for implementing, in a system that includes a graphics engine for rendering images on a display screen, a method for processing compressed graphical image data received by the graphics engine in preparation for rendering an image represented by the graphical image data, wherein less than all of the compressed graphical image data received by the graphics engine is decompressed, the computer program product comprising:

a computer-readable medium having computer-executable instructions for performing the steps of;

receiving compressed graphical image data and information specifying a boundary encompassing graphical image data that is to be rendered on the display screen, wherein a first portion of the compressed graphical image data is positioned within the boundary and is to be rendered on a scanline of the display screen and wherein a second portion of the compressed graphical image data is positioned outside the boundary and is not to be rendered on the display screen;

mapping the first portion of the compressed graphical image data to pixels of a scanline of the display screen prior to the first portion of the compressed graphical image data being decompressed;

decompressing the first portion of the compressed graphical image data that has been mapped to the pixels of the scanline so as to identify display parameters to be assigned to the pixels and translucence parameters specifying a relative weight to be given to the display parameters with respect to any data previously stored at a scanline buffer associated with the scanline;

compositing the display parameters to the scanline buffer using the translucence parameters; and

transmitting the composited display parameters to the display screen to refresh the scanline as part of an operation of refreshing the display screen, wherein the display screen is refreshed without the second portion of the compressed graphical image data being decompressed.

16. A computer program product as defined in claim 14, wherein the computer-readable medium further has computer-executable instructions for performing the step of establishing communication with a remote server, wherein the compressed graphical image data is received from the remote server.

17. A computer program product as defined in claim 14, wherein the step of establishing communication with the remote server comprises the step of accessing the Internet.

18. A computer program product as defined in claim 14, wherein the computer-readable medium further has computer-executable instructions for performing the steps of:

reading one of a plurality of vector data structures included in the compressed graphical image data; and

identifying an entry in a decompression codebook, the entry being referenced by said one of the plurality of vector data structures, the entry specifying the display parameters.

19. In a processor capable of transmitting signals to a display screen so as to generate an image on the display screen, the processor having two scanline buffers each capable of storing display parameters to be used to refresh one scanline of the display screen, a method for decompressing and compositing graphical image data comprising the steps of:

receiving compressed graphical image data and receiving cel data structures, each cel data structure being associated with a subset of the compressed graphical image data and defining a region of the display screen on which the associated subset is to be rendered;

determining which of the cel data structures define a region of the display screen that includes a segment of the first scanline;

using the cel data structures that define said region of the display screen that includes the segment of the first scanline, mapping a first portion of the compressed graphical image data to pixels on the first scanline of the display screen;

decompressing the first portion of the compressed graphical image data so as to identify first display parameters to be assigned to the pixels on the first scanline;

compositing the first display parameters to a first scanline buffer;

transmitting the composited first display parameters to the display screen;

mapping a second portion of the compressed graphical image data to pixels on a second scanline of the display screen;

decompressing the second portion of the compressed graphical image data so as to identify first display parameters to be assigned to the pixels on the second scanline;

compositing the second display parameters to a second scanline buffer; and

transmitting the composited second display parameters to the display screen.

20. A computer program product for implementing a method of decompressing and compositing graphical image data, wherein the method is implemented in a processor capable of transmitting signals to a display screen so as to generate an image on the display screen, the computer program product comprising:

a computer-readable medium having computer-executable instructions for performing the steps of;

receiving compressed graphical image data;

mapping a portion of the compressed graphical image data to pixels on a scanline of the display screen;

decompressing the portion of the compressed graphical image data so as to identify display parameters to be assigned to the pixels, the display parameters including;

color values to be assigned to the pixels; and

a translucence parameter, the value of which specifies a relative weight to be given to the display parameters with respect to other data previously stored at a scanline buffer;

compositing the display parameters to a scanline buffer, by combining the display parameters with other data previously stored at the scanline buffer according to the relative weight given to the display parameters with respect to said other data as specified by the translucence parameter; and

initiating transmission of the display parameters to the display screen.

15. A computer program product as defined in claim 21, wherein the step of decompressing the first portion of the compressed graphical image data comprises the step of identifying display parameters including Y, Cr, and Cb values to be assigned to the pixels.

21. A computer program product as defined in claim 20, wherein the color values include Y, Cr, and Cb values to be assigned to the pixels.

22. In a processor capable of generating an image on the display screen, a method for decompressing and compositing image data comprising the steps of:

receiving compressed image data and cel data structures, wherein each cel data structure is associated with a subset of the compressed image data and defines a region of the display screen on which the associated subset is to be rendered;

mapping a portion of the compressed image data to pixels of a scanline of the display screen prior to the portion of the compressed image data being decompressed, wherein the mapping includes determining which of the cel data structures define a region of the display screen that includes a segment of the scanline;

decompressing the portion of the compressed image data that has been mapped to the pixels of the scanline so as to identify display parameters to be assigned to the pixels; and

compositing the display parameters to a scanline buffer that is to be used to refresh the scanline.

23. A method as defined in claim 22, wherein only portions of the compressed image data that are mapped to scanlines of the display screen are decompressed.

24. A method as defined in claim 22, further comprising the steps of:

mapping a second portion of the compressed image data to pixels of a second scanline of the display screen prior to the second portion of the compressed image data being decompressed, wherein the mapping includes determining which of the cel data structures define a region of the display screen that includes a segment of the second scanline;

decompressing the second portion of the compressed image data that has been mapped to the pixels of the second scanline so as to identify display parameters to be assigned to the pixels of the second scanline; and

compositing the display parameters to a second scanline buffer that is to be used to refresh the second scanline.

25. A method as defined in claim 22, wherein the step of mapping the portion of the compressed image data comprises the step of identifying addresses associated with a memory device, the addresses being assigned to the portion of the compressed image data.

26. In a processor capable of generating an image on the display screen, a method for decompressing and compositing image data comprising the steps of:

receiving compressed image data;

mapping a portion of the compressed image data to pixels of a scanline of the display screen prior to the portion of the compressed image data being decompressed;

decompressing the portion of the compressed image data that has been mapped to the pixels of the scanline so as to identify display parameters to be assigned to the pixels and translucence parameters specifying a relative weight to be given to the display parameters with respect to any data previously stored at a scanline buffer that is to be used to refresh the scanline; and

compositing the display parameters to the scanline buffer using the translucence parameters.

27. A method as defined in claim 26, further comprising the step of receiving information specifying a boundary encompassing image data that is to be rendered on the display screen, wherein a first portion of the compressed image data is positioned within the boundary and is to be rendered on a scanline of the display screen and wherein a second portion of the compressed image data is positioned outside the boundary and is not to be rendered on the display screen.

28. A method as defined in claim 27, further comprising refreshing the display screen using the composited display parameters, wherein the display screen is refreshed without the second portion of the compressed image data having been decompressed.

29. A method as defined in claim 26, further comprising the step of receiving cel data structures, each being associated with a subset of the compressed image data and defining a region of the display screen on which the associated subset is to be rendered.

30. A method as defined in claim 29, wherein the step of mapping comprises the step of determining which of the cel data structures define a region of the display screen that includes a segment of the scanline.