Caching coverage values for rendering text using anti-aliasing techniques

• US 9,171,386 B2
• Filed: 10/11/2011
• Issued: 10/27/2015
• Est. Priority Date: 10/11/2011
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Inventors: Jain, Megha, Cohen, Miles M., Brown, Robert A., Chaoweeraprasit, Worachai, Precious, Andrew M., VedBrat, Kanwal
• Primary Examiner(s): Liu, Zhengxi
• Application Number:
  US13/270,926
• Publication Number:
  US 20130088505A1
• Time in Patent Office: 1,477 Days
• US Class Current: 1/1
• CPC Class Codes: G06T 11/203 Drawing of straight lines or curves
• CPC Class Codes: G06T 2200/12 involving antialiasing
• CPC Class Codes: G09G 2320/0276 for the purpose of adaptation to the characteristics of a display device, i.e. gamma correction
• CPC Class Codes: G09G 2340/0457 Improvement of perceived resolution by subpixel rendering
• CPC Class Codes: G09G 2340/10 Mixing of images, i.e. displayed pixel being the result of an operation, e.g. adding, on the corresponding input pixels
• CPC Class Codes: G09G 2360/121 using a cache memory
• CPC Class Codes: G09G 5/026 Control of mixing and/or overlay of colours in general G09G5/022 and G09G5/024 take precedence
• CPC Class Codes: G09G 5/28 for enhancement of character form, e.g. smoothing

Abstract

Techniques for calculating sub-pixel coverage values for text to be displayed, so as to enable caching of the sub-pixel coverage values. The sub-pixel coverage values may enable a linear combination of color information for the text with color information for one or more other, overlapping display elements for calculating composite color values to be used in controlling a display. Such composite color values to be used in controlling sub-pixels of a display may be calculated, in some embodiments, without performing a gamma correction process. Also described are techniques for retrieving cached sub-pixel coverage values and combining the values with color information for text and for other, overlapping display elements to calculate composite color values for sub-pixels of a display. At least one graphics processing unit (GPU) may be configured to perform operations using the sub-pixel coverage information and to calculate the composite color values for the sub-pixels.

Claims

1. A method of processing text that will be displayed in a graphical interface of a computing device, the method comprising:

creating a mapping for the text, the mapping comprising information representing at least one shape of the text and corresponding to a plurality of sub-pixels of a display to be used in displaying the text;

determining initial sub-pixel coverage values for the plurality of sub-pixels using a sub-pixel anti-aliasing technique;

processing the initial sub-pixel coverage values to yield processed sub-pixel coverage values for a plurality of pixels of image data corresponding to the plurality of sub-pixels; and

caching the processed sub-pixel coverage values for subsequent use in rendering the text in the graphical interface in a video memory organized in accordance with a format that includes a red channel from which a graphics processing unit (GPU) of the computing device is natively configured to retrieve red sub-pixel color values, a green channel from which the GPU of the computing device is natively configured to retrieve green sub-pixel color values, and a blue channel from which the GPU of the computing device is natively configured to retrieve blue sub-pixel color values, wherein the caching includes caching the processed sub-pixel coverage values in at least one of the red channel, the blue channel, or the green channel.

2. The method of claim 1, wherein caching the processed sub-pixel coverage values comprises storing the processed sub-pixel coverage values in the video memory without storing information on a color with which the text is to be displayed in the graphical interface in the video memory.

3. The method of claim 1, wherein the video memory includes a BGRA surface data structure.

4. The method of claim 3, further comprising:

reconfiguring the GPU to retrieve the cached processed sub-pixel coverage values from the video memory.

5. The method of claim 1, wherein processing the initial sub-pixel coverage values to yield the processed coverage values comprises adjusting the initial sub-pixel coverage values so as to compensate for nonlinearities of the display on which the graphical interface is to be displayed.

6. The method of claim 5, further comprising rendering the text in the graphical interface on the display without performing a gamma correction process at a time of the rendering of the text.

7. The method of claim 5, wherein adjusting the initial sub-pixel coverage values so as to compensate for nonlinearities comprises modifying the initial sub-pixel coverage values so as to enable composite color values for controlling the display to be calculated by linearly combining the initial sub-pixel coverage values and color values for the text with color values for at least one other display element that is to be displayed overlapping with the text.

8. The method of claim 1, wherein the creating, determining, processing, and caching are performed in response to receiving from an executing process an instruction comprising at least content of the text and not including a position on the display at which the text is to be rendered.

9. An apparatus, comprising:

at least one processor programmed to;

in response to receiving a request to render text for a display, retrieve from a cache sub-pixel coverage values for the text, the cache having a red channel from which at least one graphics processing unit (GPU) of the apparatus is natively configured to retrieve red sub-pixel color values, a green channel from which the at least one GPU of the apparatus is natively configured to retrieve green sub-pixel color values, and a blue channel from which the at least one GPU of the apparatus is natively configured to retrieve blue sub-pixel color values, wherein the sub-pixel coverage values for the text are stored in at least two of the red, blue, or green channels;

configure the at least one GPU to determine composite color values for pixels of the display at which the text is to be displayed, the configuring comprising configuring the at least one GPU to retrieve the sub-pixel coverage values from the at least two of the red, green, or blue channels;

receive from the at least one GPU the composite color values for the pixels at which the text is to be displayed; and

render, based on the composite color values, an anti-aliased version of the text to the display.

10. The apparatus of claim 9, wherein the at least one processor is programmed to configure the at least one GPU to determine the composite color values for the pixels at least in part by linearly combining color values for the text, as modified by the sub-pixel coverage values, and color values for at least one other display element that is to be displayed overlapping with the text on the display.

11. The apparatus of claim 10, wherein the at least one processor is programmed to configure the at least one GPU to determine the composite color values without performing a render-time gamma correction process.

12. The apparatus of claim 10, wherein the at least one other display element is a background graphic over which the text is to be superimposed on the display, and

wherein the at least one processor is programmed to receive the request to render the text in response to a user animating the text on the display so as to move the text relative to the background graphic.

13. The apparatus of claim 9, wherein the at least one processor is programmed to configure the at least one GPU to determine a composite color value for a pixel of the display based at least in part on the sub-pixel coverage values for the pixel from the cache and on sub-pixel color values for the pixel from another source, the other source being arranged in accordance with a hardware organization from which the at least one GPU of the apparatus is natively configured to retrieve sub-pixel color values.

14. The apparatus of claim 13, wherein the at least one processor is further programmed to receive the request to render the text to the display, the request comprising the sub-pixel color values.

15. The apparatus of claim 13, wherein the at least one processor is further programmed to, in response to receiving the request, retrieve the sub-pixel color values.

16. At least one computer-readable storage medium encoded with computer-executable instructions that, when executed by a computer, cause the computer to carry out a method of processing text that will be displayed in a graphical interface of a computing device, the method comprising:

creating a mapping for the text, the mapping comprising information representing at least one shape of the text and corresponding to a plurality of sub-pixels of a display to be used in displaying the text;

calculating sub-pixel coverage values for the plurality of sub-pixels using a sub-pixel anti-aliasing technique; and

caching, in a memory organized in a format that includes a red channel from which graphics processing unit (GPU) of the computing device is natively configured to retrieve red sub-pixel color values, a green channel from which the GPU of the computing device is natively configured to retrieve green sub-pixel color values, and a blue channel from which the GPU of the computing device is natively configured to retrieve blue sub-pixel color values, the sub-pixel coverage values for subsequent use in rendering the text in the graphical interface, wherein the caching includes caching the processed sub-pixel coverage values in at least one of the red channel, the blue channel, or the green channel.

17. The at least one computer-readable storage medium of claim 16, wherein calculating the sub-pixel coverage values comprises adjusting initial sub-pixel coverage values, output by the sub-pixel anti-aliasing technique, so as to compensate for nonlinearities of the display.

18. The at least one computer-readable storage medium of claim 17, wherein adjusting the initial sub-pixel coverage values so as to compensate for nonlinearities of the display comprises modifying the initial sub-pixel coverage values so as to enable composite color values for controlling the display to be calculated by linearly combining the initial sub-pixel coverage values and color values for the text with color values for at least one other display element that is to be displayed overlapping with the text.

19. The at least one computer-readable storage medium of claim 16, wherein caching the processed sub-pixel coverage values for the text comprises storing the processed sub-pixel coverage values in the memory without storing in the memory information on a color with which the text is to be displayed in the graphical interface.

20. The at least one computer-readable storage medium of claim 16, wherein caching the processed sub-pixel coverage values for the text comprises storing the processed sub-pixel coverage values in another memory for storing color values of display elements to be rendered, the other memory having an organization of values corresponding to a hardware organization of at least one GPU of the computer.