IMPLEMENTING COMPOSITING OPERATIONS ON IMAGES

• US 20070126753A1
• Filed: 10/20/2006
• Published: 06/07/2007
• Est. Priority Date: 10/31/2005
• Status: Active Grant

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Danilo, Alexander, MOORE, Kevin, Northway, Craig
• Granted Patent: US 7,965,299 B2
• Time in Patent Office: Days
• US Class Current: 345/592
• CPC Class Codes: G06T 15/503 Blending, e.g. for anti-aliasing

Abstract

A method is described of compositing graphic elements in a pixel-based renderer (18). A first graphic element is received (step 2601) having a first colour and a first opacity and a second graphic element is received (step 2602) having a second colour and a second opacity. A blend output is obtained from a blend function dependent on the first colour and the second colour; and a resultant colour is determined (step 2603) of a compositing operation on the first and second graphic elements, the resultant colour being dependent on the blend output and otherwise being independent of the second colour.

Claims

1. A method of compositing graphic elements in a pixel-based renderer, said method comprising the steps of:

receiving a first graphic element having a first colour and a first opacity and a second graphic element having a second colour and a second opacity;

determining a blend output of a blend function dependent on the first colour and the second colour; and

determining a resultant colour of a compositing operation on the first and second graphic elements, the resultant colour being dependent on the blend output and otherwise being independent of the second colour.

2. A method according to claim 1 comprising the further step of determining a resultant opacity of the compositing operation, the resultant opacity being equal to the first opacity.

3. A method according to claim 1 comprising the further step of determining a resultant opacity of the compositing operation, the resultant opacity being equal to a product of the first opacity and the second opacity.

4. A method according to claim 1 wherein the compositing operation is a modified Porter and Duff atop operation.

5. A method according to claim 1 wherein the compositing operation is a modified Porter and Duff in operation.

29. The method according to claim 1, wherein the output of the blend function is independent of the first opacity and the resultant colour is independent of the first opacity.

30. The method according to claim 1, wherein said determining step comprises the sub-steps of:

compositing the first graphic element with the second graphic element using a first operator to produce a first intermediate result;

compositing the first graphic element with the second graphic element using a second blend operation that is different to the blend operation to produce a second intermediate result, said second blend operation using said blend output; and

combining the first intermediate result with the second intermediate result to produce said resultant colour.

6. A method of implementing a blend operation using a first graphic element comprising a first colour and a first opacity and a second graphic element comprising a second colour and a second opacity using a blend function that operates on the first and second colours independently of their respective opacities and a compositing operator to produce a resultant colour, characterised in that the contribution of the second colour to the resultant colour is independent of the first opacity of the first graphic element.

7. A method according to claim 6, said method comprising the steps of:

compositing the first graphic element with the second graphic element using a first operator to produce a first intermediate result;

compositing the first graphic element with the second graphic element using a second blend operation that is different to the blend operation to produce a second intermediate result; and

combining the first intermediate result with the second intermediate result to produce said resultant colour.

8. A method according to claim 7 wherein the blend operation and the second blend operation both include said blend function.

9. A method according to claim 7 wherein the blend operation is based on a Porter and Duff atop operation and the second blend operation is based on a Porter and Duff over operation.

10. A method according to claim 9 wherein the first operator is a Porter and Duff src-out operator and said combining step subtracts the first intermediate result from the second intermediate result.

11. A method according to claim 7 wherein the blend operation is based on a Porter and Duff in operation and the second blend operation is based on a Porter and Duff over operation.

12. A method according to claim 11 wherein the first operator is a Porter and Duff xor operator and said combining step subtracts the first intermediate result from the second intermediate result.

13. A method according to claim 7 wherein the blend operation is based on a Porter and Duff over operation and the second blend operation is based on a Porter and Duff atop operation.

14. A method according to claim 13 wherein the first operator is a Porter and Duff src-out operator and said combining step adds the first intermediate result to the second intermediate result.

15. A method according to claim 7 wherein the blend operation is based on a Porter and Duff in operation and the second blend operation is based on a Porter and Duff atop operation.

16. A method according to claim 15 wherein the first operator is a Porter and Duff dst-out operator and said combining step subtracts the first intermediate result from the second intermediate result.

17. A method according to claim 7 wherein the blend operation is based on a Porter and Duff over operation and the second blend operation is based on a Porter and Duff in operation.

18. A method according to claim 17 wherein the first operator is a Porter and Duff xor operator and said combining step adds the first intermediate result to the second intermediate result.

19. A method according to claim 7 wherein the blend operation is based on a Porter and Duff atop operation and the second blend operation is based on a Porter and Duff in operation.

20. A method according to claim 19 wherein the first operator is a Porter and Duff dst-out operator and said combining step adds the first intermediate result to the second intermediate result.

21. The method according to claim 6, wherein the compositing operator is a modified Porter and Duff atop operator.

22. The method according to claim 6, wherein the compositing operator is a modified Porter and Duff in operator.

23. The method according to claim 21, implemented in a pixel sequential rendering system by setting flags to indicate that regions of interest for the compositing are ‘

source intersect destination’ and

‘

destination outside source’ and

wherein an independent operation code specifies the blend function.

24. The method according to claim 22, implemented in a pixel sequential rendering system by setting flags to indicate that a region of interest for the compositing is ‘

source intersect destination’ and

wherein an independent operation code specifies the blend function.

25. The method according to claim 21, implemented in a framestore rendering system whereby the first and second graphic elements are combined such that the resultant colour is the sum of two terms, the first term being a product of the second opacity and a result of the blend function, the second term being a product of the complement of the second opacity and the first colour, and wherein the resultant opacity is equal to the first opacity.

26. The method according to claim 22, implemented in a framestore rendering system whereby the first and second graphic elements are combined such that the resultant colour is a result of the blending function, and wherein the resultant opacity is equal to the product of the first and second opacities.

27. The method according to claim 4 or claim 21, wherein the Porter and Duff atop operator is modified such that the colour in the region where both objects are opaque is given by the blend output.

28. The method according to claim 5 or claim 22, wherein the Porter and Duff in operator is modified such that the colour in the region where both objects are opaque is given by the blend output.

31. An apparatus for compositing graphic elements in a pixel-based renderer, said apparatus comprising:

means for receiving a first graphic element having a first colour and a first opacity and a second graphic element having a second colour and a second opacity;

means for determining a blend output of a blend function dependent on the first colour and the second colour; and

means for determining a resultant colour of a compositing operation on the first and second graphic elements, the resultant colour being dependent on the blend output and otherwise being independent of the second colour.

32. A computer program product comprising machine-readable program code recorded on a machine-readable recording medium, for controlling the operation of a data processing apparatus on which the program code executes to perform a method of compositing graphic elements in a pixel-based renderer, said method comprising the steps of:

receiving a first graphic element having a first colour and a first opacity and a second graphic element having a second colour and a second opacity;

determining a blend output of a blend function dependent on the first colour and the second colour; and

determining a resultant colour of a compositing operation on the first and second graphic elements, the resultant colour being dependent on the blend output and otherwise being independent of the second colour.

33. A computer program comprising machine-readable program code for controlling the operation of a data processing apparatus on which the program code executes to perform a method of compositing graphic elements in a pixel-based renderer, said method comprising the steps of:

receiving a first graphic element having a first colour and a first opacity and a second graphic element having a second colour and a second opacity;

determining a blend output of a blend function dependent on the first colour and the second colour; and

determining a resultant colour of a compositing operation on the first and second graphic elements, the resultant colour being dependent on the blend output and otherwise being independent of the second colour.