Method and apparatus for rendering sub-pixel anti-aliased graphics on stripe topology color displays

• US 6,384,839 B1
• Filed: 09/21/1999
• Issued: 05/07/2002
• Est. Priority Date: 09/21/1999
• Status: Expired due to Term

• Current Assignee: Imaging Holdings Corp (Monotype Imaging Holdings, Inc.)
• Original Assignee: Agfa Monotype Corp. (Monotype Imaging Inc)
• Inventors: Paul, Steven William
• Primary Examiner(s): Brier, Jeffery
• Assistant Examiner(s): PATEL, GAUTAM
• Application Number:
  US09/400,153
• Time in Patent Office: 959 Days
• Field of Search: 345/613, 345/441-443, 345/136, 345/152
• US Class Current: 345/613
• CPC Class Codes: G06T 11/203 Drawing of straight lines or curves
• CPC Class Codes: G09G 2340/0457 Improvement of perceived resolution by subpixel rendering

Abstract

An anti-aliasing method and apparatus for use with a stripe topology color display provides sub-pixel level smoothing in a manner which enhances the apparent resolution of the display, yielding enhanced object shape and positioning, while maintaining accurate foreground and background colors. The method or apparatus includes the steps or means of: generating a 1 bit per pixel super-sampled bitmap for the image, in which there is greater than or equal to 1 bit for each sub-pixel of the image; determining an average intensity I for each position of the image from the bitmap; determining a sub-pixel intensity S for each sub-pixel using the average intensity I, a foreground intensity F and a background intensity B; and setting a sub-pixel value V for each sub-pixel to produce the sub-pixel intensity on the display.

Claims

1. A method of displaying an image on a stripe topology color display using sub-pixel anti-aliasing, the method comprising:

generating a 1 bit per pixel super-sampled bitmap for the image, in which there is greater than or equal to 1 bit for each sub-pixel of the image;

determining an average intensity I for each position of the image from the bitmap;

determining a sub-pixel intensity S for each said sub-pixel using the average intensity I, a foreground intensity F and a background intensity B; and

setting a sub-pixel value V for each said sub-pixel to produce the sub-pixel intensity on the display.

2. The method of claim 1 wherein the super-sampled bitmap is generated at the normal vertical resolution and 3 times the normal horizontal resolution.

3. The method of claim 2 wherein the average intensity for each said sub-pixel is determined by taking a 5 wide center weighted average at each bit in the super-sampled bitmap.

4. The method of claim 1 wherein the sub-pixel intensity S is determined from the average intensity ‘

I’

, the foreground intensity ‘

F’

, the background intensity ‘

B’

, and the maximum intensity I_max as;

5. The method of claim 1 wherein the sub-pixel value for each said sub-pixel is determined as:

6. The method of claim 1 wherein the foreground intensity and the background intensity are determined using a table lookup from pairs of x-intercept data generated during rasterization of a character outline.

7. A computer-readable medium having code to cause a computer system to display an image on a stripe topology color display using sub-pixel anti-aliasing, the code operating by:

generating a 1 bit per pixel super-sampled bitmap for the image, in which there is greater than or equal to 1 bit for each sub-pixel of the image;

determining an average intensity I for each position of the image from the bitmap;

determining a sub-pixel intensity S for each said sub-pixel using the average intensity I, a foreground intensity F and a background intensity B; and

setting a sub-pixel value V for each said sub-pixel to produce the sub-pixel intensity on the display.

8. The computer-readable medium of claim 7 wherein the super-sampled bitmap is generated at the normal vertical resolution and 3 times the normal horizontal resolution.

9. The computer-readable medium of claim 8 wherein the average intensity for each said sub-pixel is determined by taking a 5 wide center weighted average at each bit in the super-sampled bitmap.

10. The computer-readable medium of claim 7 wherein the sub-pixel intensity S is determined from the average intensity ‘

I’

, the foreground intensity ‘

F’

, the background intensity ‘

B’

, and the maximum intensity I_max as;

11. The computer-readable medium of claim 7 wherein the sub-pixel value for each said sub-pixel is determined as:

12. The computer-readable medium of claim 7 wherein the foreground intensity and the background intensity are determined using a table lookup from pairs of x-intercept data generated during rasterization of a character outline.

13. A system for displaying an image on a stripe topology color display using sub-pixel anti-aliasing, the system comprising:

means for generating a 1 bit per pixel super-sampled bitmap for the image, in which there is greater than or equal to 1 bit for each sub-pixel of the image;

means for determining an average intensity I for each position of the image from the bitmap;

means for determining a sub-pixel intensity S for each said sub-pixel using the average intensity I, a foreground intensity F and a background intensity B; and

means for setting a sub-pixel value V for each said sub-pixel to produce the sub-pixel intensity on the display.

14. The system of claim 13 wherein the super-sampled bitmap is generated at the normal vertical resolution and 3 times the normal horizontal resolution.

15. The system of claim 14 wherein the average intensity for each said sub-pixel is determined by taking a 5 wide center weighted average at each bit in the super-sampled bitmap.

16. The system of claim 13 wherein the sub-pixel intensity S is determined from the average intensity ‘

I’

, the foreground intensity ‘

F’

, the background intensity ‘

B’

, and the maximum intensity I_max as;

17. The system of claim 13 wherein the sub-pixel value for each said sub-pixel is determined as:

18. The system of claim 13 wherein the foreground intensity and the background intensity are determined using a table lookup from pairs of x-intercept data generated during rasterization of a character outline.