Method and apparatus for display image rotation

• US RE38,471 E1
• Filed: 12/29/2000
• Issued: 03/23/2004
• Est. Priority Date: 09/27/1996
• Status: Expired due to Term

• Current Assignee: Apple Inc.
• Original Assignee: Apple Computer Incorporated (Apple Inc.)
• Inventors: Bailey, Robert L., Howard, Brian D.
• Primary Examiner(s): Tung, Kee M.
• Application Number:
  US09/753,173
• Time in Patent Office: 1,180 Days
• Field of Search: 345/564, 345/568, 345/566, 345/571, 345/649, 345/656, 345/658, 345/659, 382/296, 382/297
• US Class Current: 345/571
• CPC Class Codes: G09G 2340/0492 Change of orientation of the displayed image, e.g. upside-down, mirrored
• CPC Class Codes: G09G 5/393 Arrangements for updating the contents of the bit-mapped memory

Abstract

A method and an apparatus for rotating images on a computer system is disclosed. The system includes a processor for accessing an image frame buffer using a set of CPU addresses, a memory for storing the frame buffer, a controller for directing the pixel data of the frame buffer to a display device using a set of controller addresses. The two sets of addresses are not necessarily the same. In fact, numerous advantages could be had from manipulating those two sets of addresses resulting in image rotation operations for the display device.

Claims

1. A computer display system including a processor and a display system, the display system having a memory, said display system comprising:

a display means for displaying image information to be arranged in a plurality of horizontal lines of pixel data;

a frame buffer containing the for storing pixel data of an image information, the frame buffer being stored in the memory in a manner that data of each of the plurality of horizontal lines including pixel data for the display means being stored in the memory resulting in the frame buffer occupying in a contiguous block in the a memory, and , the frame buffer further being accessible by the a processor using a processor address set of row and column addresses;

a controller means for establishingfor determining new row addresses of a controller address set as the column addresses of the processor address set, and establishing new column address of the controller address set as the row addresses of the processor address set;

the controller means being coupled to the display means for transferring adapted to transfer the pixel data of the frame buffer to the a display means using the new controller address set, the controller means setting each of the new row addresses of the controller address set as the difference between its current value and a maximum value of the new row addresses of the controller address set and providing the pixel data of the frame buffer to the display means while referencing both the new row addresses and the new column addresses of the controller address set in an ascending order.

2. The computer display system of claim 1 wherein the maximum value of the new row addresses of the controller address set refers to the maximum row address where the pixel data displayable on the display means are stored in the memory.

3. The computer system of claim 1 wherein A display system comprising:

4. The computer display system of claim 3 wherein the maximum value of the new column address of the controller address set refers to the maximum column address where the pixel data displayable on the display means are stored in the memory.

5. A method for rotating images for a computer system, the computer system including a processor, and a display system, the display system having and a memory, said method comprising the steps of:

displaying image information on display means arranged in a plurality of horizontal lines of pixel data;

storing pixel data of an image in a frame buffer in the memory, the frame buffer containing the image information , the frame buffer being stored in the memory in a manner such that data of each of the plurality of horizontal lines including pixel data for the display means are stored in the memory resulting in the frame buffer occupying a contiguous block in the memory and the frame buffer further being accessible by the processor using a processor address set of row and column addresses;

establishingdetermining new row addresses of a controller address set as the column addresses of the processor address set, and establishing new column addresses of the controller address set as the row addresses of the processor address set;

transferring the pixel data of from the frame buffer to the display means using the new controller address set, the transferring step setting each of the new row addresses of the controller address set as the difference between its current value and a maximum value of the new row addresses of the controller address set and providing the pixel data of from the frame buffer to the display means while referencing both the subtracted-from-maximum new row addresses and the new column addresses of the controller address set in an ascending order.

6. The method of claim 5 wherein the maximum value of the new row addresses of the controller address set refers to the maximum row address where the pixel data displayable on the display means are stored in the memory.

7. The method of claim 5 wherein the transferring step further includes A method for rotating images for a computer system, the computer system including a processor, a display and a memory, said method comprising the steps of:

8. The method of claim 7 wherein the maximum value of the new column addresses of the controller address set refers to the maximum column address where the pixel data displayable on the display means are stored in the memory.

9. A graphics controller for rotating an image comprising:

10. An apparatus for manipulating a processor'"'"'s addressing of an image from a frame buffer so that the image is rotated 90 degrees counter clockwise without requiring the processor to spend its cycles on address transformation operations, the apparatus comprising:

11. The frame buffer interface of claim 10 wherein the frame buffer for which the frame buffer interface is transferring pixel data is stored in a memory in a manner such that data of each of the plurality of horizontal lines including pixel data to be displayed on the display is stored in the memory resulting in the frame buffer occupying a contiguous block in the memory and the frame buffer is further accessible by a processor using a processor address set and row and column addresses.

12. An apparatus for manipulating a processor'"'"'s addressing of an image from a frame buffer so that the image is rotated 90 degrees clockwise without requiring the processor to spend its cycles on address transformation operations, the apparatus comprising:

13. The frame buffer interface of claim 12 wherein the frame buffer for which the frame buffer interface is transferring pixel data is stored in a memory in a manner such that data of each of the plurality of horizontal lines including pixel data to be displayed on the display is stored in the memory resulting in the frame buffer occupying a contiguous block in the memory and the frame buffer is further accessible by a processor using a processor address set and row and column addresses.

14. A system for rotating an image comprising:

15. A method of rotating an image, the image comprising a plurality of pixels, each pixel having a row address R and a column address C, the method comprising:

16. A method for rotating images 90 degrees counter clockwise comprising the steps of:

17. A method for rotating images 90 degrees clockwise comprising the steps of: