ANTIALIASING OF TWO-DIMENSIONAL VECTOR IMAGES

• US 20090102857A1
• Filed: 10/23/2007
• Published: 04/23/2009
• Est. Priority Date: 10/23/2007
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Kallio, Kiia K.
• Granted Patent: US 8,638,341 B2
• Time in Patent Office: Days
• US Class Current: 345/611
• CPC Class Codes: G06F 2203/04804 Transparency, e.g. transparent or translucent windows
• CPC Class Codes: G06T 11/40 Filling a planar surface by adding surface attributes, e.g. colour or texture
• CPC Class Codes: G06T 15/503 Blending, e.g. for anti-aliasing
• CPC Class Codes: G09G 5/14 Display of multiple viewports

Abstract

Described is a method of rendering an image. A transparency of a destination pixel and a transparency of a source pixel are determined at multiple sample positions in each pixel. A new pre-multiplied color is determined for the destination pixel in response to the transparencies of the destination pixel, the transparencies of the source pixel, a color of the source pixel and a pre-multiplied color of the destination pixel. New transparencies of the destination pixel are determined at the samples in the destination pixel in response to the transparencies of the source pixels and the transparencies of the destination pixel. The method of the present invention permits rendering of polygonal two-dimensional images while eliminating overdraw, therefore using less memory bandwidth than conventional methods for rendering typical two-dimensional vector images. Thus the method is suited for mobile computing and other applications with limited memory bandwidth.

Claims

1. A method of rendering an image, the method comprising:

determining a transparency of a destination pixel at a plurality of samples in the destination pixel;

determining a transparency of a source pixel at a plurality of samples in the source pixel, the destination pixel being in front of the source pixel; and

determining a new pre-multiplied color of the destination pixel in response to the transparencies of the destination pixel, the transparencies of the source pixel, a color of the source pixel and a pre-multiplied color of the destination pixel.

2. The method of claim 1 further comprising determining a plurality of new transparencies of the destination pixel at the samples in the destination pixel in response to the transparencies of the source pixel and the transparencies of the destination pixel.

3. The method of claim 1 wherein the determinations are made for a single layer in the two-dimensional vector image, the method further comprising repeating the determinations for another layer in the two-dimensional vector image.

4. The method of claim 1 wherein the transparencies of the source pixel are determined in response to a plurality of binary values in a coverage mask and a transparency of a polygon.

5. The method of claim 1 wherein the new pre-multiplied color of the destination pixel is determined to be a pre-multiplied color of the source pixel when each destination transparency has a value of zero.

6. The method of claim 1 further comprising storing at least one of the new transparencies of the destination pixel in a palette compression format.

7. The method of claim 1 further comprising storing at least one of the new transparencies of the destination pixel in a quantized compression format.

8. A method of rendering an image, the method comprising:

determining a destination transparency A_di at a number n of samples in a destination pixel;

determining a source transparency A_si at the number n of samples in a source pixel, the source pixel being behind the destination pixel; and

calculating a new pre-multiplied color p for the destination pixel in response to a pre-multiplied destination color p_d, a source color c_s, the destination transparencies A_di and the source transparencies A_si as

$p=p_d+c_s\times <br><br>\frac{1}{n}<br><br>\underset{i=1}{\overset{n}{\sum <br><br>}}<br><br><br><br>\left(A_{\mathrm{si}}\times <br><br>\left(1-A_{\mathrm{di}}\right)\right).$

9. The method of claim 8 further comprising calculating a plurality of new transparency values A_i for the samples in the destination pixel in response to the destination transparencies A_di and the source transparencies A_si as

A_i=A_di+A_si×

(1−

A_di) where i=1 to n.

10. The method of claim 8 wherein the source transparencies are responsive to a plurality of values in a coverage mask for the source pixel.

11. The method of claim 8 wherein the determinations and calculations are made for a single layer in the two-dimensional vector image, the method further comprising repeating the determinations and calculations for another layer in the two-dimensional vector image.

12. A graphics processor for generating antialiased two-dimensional vector images comprising:

a source buffer storing, for a plurality of source pixels, a color and a plurality of transparencies of each source pixel, each transparency being associated with a sample in one of the source pixels;

a destination buffer storing, for a plurality of destination pixels, a color and a plurality of transparencies for each destination pixel, each transparency being associated with a sample in one of the destination pixels, each destination pixel being in front of a respective one of the source pixels; and

a composition module in communication with the destination buffer and the source buffer, the composition module generating a new pre-multiplied color for each destination pixel in response to the transparencies of the respective destination pixel, the transparencies of the respective source pixel, a color of the respective source pixel and a pre-multiplied color of the respective destination pixel, the composition module generating a new transparency for each destination pixel at each sample in the destination pixel in response to the transparencies of the respective source pixel and the transparencies of the respective destination pixel.

13. The graphics processor of claim 12 further comprising a display screen in communication with the composition module and the destination buffer to display the antialiased two-dimensional vector images.

14. The graphics processor of claim 12 further comprising a pixel encode buffer having a plurality of pixels, each of the pixels having at least two bits to indicate whether all the transparencies of a respective destination pixel have a value of one and whether all the transparencies of the respective destination pixel have a value of zero.

15. The graphics processor of claim 14 wherein the at least two bits further indicates whether the transparencies of the respective destination pixel are palette compressed.

16. The graphics processor of claim 14 wherein the at least two bits further indicates whether the transparencies of the respective destination pixel are quantized compressed.

17. A computer readable medium for rendering an image, the computer readable medium comprising computer executable instructions to cause a processor to:

determine a transparency of a destination pixel at a plurality of samples in the destination pixel;

determine a transparency of a source pixel at a plurality of samples in the source pixel, the destination pixel being in front of the source pixel; and

determine a new pre-multiplied color of the destination pixel in response to the transparencies of the destination pixel, the transparencies of the source pixel, a color of the source pixel and a pre-multiplied color of the destination pixel.

18. The computer readable medium of claim 17 wherein the computer executable instructions, when executed, are adapted to manufacture a device operative to perform the determinations of the transparencies of the destination pixel and the source pixel and the determination of the new pre-multiplied color of the destination pixel.