Transparency information in image or video format not natively supporting transparency

1. A method of transforming source image data for a source image, the source image data being in a source format providing native support for transparency, the method comprising:

determining, from the source image data, colour information and transparency information for each source pixel of the source image;

generating a transformed image including a first region and a second region by:

for each source pixel of the source image,

basing colour information of a corresponding pixel of the first region on the colour information of that source pixel; and

basing colour information of a corresponding pixel of the second region on the transparency information of that source pixel, including performing a geometric transformation such that at least one dimension of the second region is less than a corresponding dimension of the first region; and

saving the transformed image in a target format not providing native support for transparency.

2. The method of claim 1 , wherein the source format is a compressed format, and wherein determining comprises decompressing the source image.

3. The method of claim 1 , wherein the source format is a vector-graphic format, and wherein determining comprises:

setting dimensions of the source image; and

computing colour information and transparency information for each source pixel of the source image based on the dimensions of the source image.

4. The method of claim 1 , wherein the target format is a compressed format, and wherein saving comprises compressing the transformed image.

5. The method of claim 4 , wherein compressing comprises applying a transform to colour information for blocks of pixels to obtain frequency-domain information.

6. The method of claim 1 , wherein the colour information of each pixel of the first region equals the colour information of the source pixel corresponding to that pixel of the first region.

7. The method of claim 1 , wherein the colour information of each pixel of the second region comprises three equal colour components.

8. The method of claim 1 , wherein the first region is disjoint from the second region.

9. The method of claim 8 , wherein the first region and the second region are adjacent regions.

10. The method of claim 1 , wherein the transformed image comprises at least part of a corresponding frame of a transformed video.

11. The method of claim 10 , wherein a first frame of the transformed video comprises the first region and a second frame of the transformed video comprises the second region.

12. A method of superimposing a partially transparent overlay image on a base image, an overlay representation of the overlay image being in a format not providing native support for transparency, the overlay representation including a first region of pixels—whose colour information represents colour information of corresponding pixels of the overlay image—and a second region of pixels —whose colour information represents transparency information of corresponding pixels of the overlay image, the method comprising:

for each base pixel in the base image:

determining first colour information from the colour information of that base pixel;

determining second colour information from the colour information of at least one corresponding pixel of the first region of the overlay representation;

determining transparency information from the colour information of at least one corresponding pixel of the second region of the overlay representation, including performing a geometric transformation on the second region of the overlay image, wherein at least one dimension of the second region is less than a corresponding dimension of the first region; and

computing colour information for a corresponding pixel of a composited image by combining the first colour information, the second colour information, and the transparency information; and

saving the composited image in a format not providing native support for transparency.

13. The method of claim 12 , wherein computing colour information comprises computing a weighted average of the first colour information and the second colour information, the weighting being determined by the transparency information.

14. The method of claim 12 , further comprising determining the locations of the first region and of the second region within the overlay representation.

15. The method of claim 12 , wherein at least one of the base image and the overlay representation is in a compressed format, and wherein the method further comprises decompressing the at least one of the base image and the overlay representation.

16. The method of claim 15 , wherein compressing comprises applying a transform to colour information for blocks of pixels to obtain frequency-domain information.

17. The method of claim 12 , wherein the format of the composited image is a compressed format, and wherein saving comprises compressing the composited image.

18. The method of claim 12 , wherein determining the transparency information comprises using a predetermined colour component of the colour information of the corresponding pixel of the second region of the overlay representation.

19. The method of claim 12 , wherein determining the transparency information comprises averaging colour components of the colour information of the corresponding pixel of the second region of the overlay representation.

20. The method of claim 12 , wherein at least one dimension of the overlay image is different than the corresponding dimension of the base image, and wherein determining the second colour information and determining the transparency information each comprise a scaling operation based on the dimensions of the overlay image and of the base image.

21. The method of claim 12 , wherein the base image comprises at least part of a frame of a base video, and wherein the composited image comprises at least part of a corresponding frame of a composited video.

22. The method of claim 12 , wherein the overlay representation comprises at least part of a frame of an overlay representation video.

23. The method of claim 12 , wherein the geometric transformation comprises a scaling operation.

24. An electronic device comprising:

memory; and

a processor coupled to the memory, the processor configured to:

determine, from source image data, colour information and transparency information for each source pixel of a source image, the source image data being in a source format providing native support for transparency;

generate a transformed image including a first region and a second region by:

for each source pixel of the source image,

basing colour information of a corresponding pixel of the first region on the colour information of that source pixel; and

basing colour information of a corresponding pixel of the second region on the transparency information of that source pixel, including performing a geometric transformation such that at least one dimension of the second region to be less than a corresponding dimension of the first region; and

save the transformed image in a target format not providing native support for transparency.

25. An electronic device comprising:

memory; and

a processor coupled to the memory, the processor configured to:

superimpose a partially transparent overlay image on a base image, an overlay representation of the overlay image being in a format not providing native support for transparency, the overlay representation including a first region of pixels—whose colour information represents colour information of corresponding pixels of the overlay image—and a second region of pixels—whose colour information represents transparency information of corresponding pixels of the overlay image, by, for each base pixel in the base image:

determining first colour information from the colour information of that base pixel;

determining second colour information from the colour information of at least one corresponding pixel of the first region of the overlay representation;

determining transparency information from the colour information of at least one corresponding pixel of the second region of the overlay representation, including performing a geometric transformation on the second region of the overlay image, wherein at least one dimension of the second region is less than a corresponding dimension of the first region; and

computing colour information for a corresponding pixel of a composited image by combining the first colour information, the second colour information, and the transparency information; and

save the composited image in a format not providing native support for transparency.

26. A non-transitory computer-readable medium storing processor-executable instructions that when executed cause a processor to:

determine, from source image data, colour information and transparency information for each source pixel of a source image, the source image data being in a source format providing native support for transparency;

generate a transformed image including a first region and a second region by:

for each source pixel of the source image,

basing colour information of a corresponding pixel of the first region on the colour information of that source pixel; and

basing colour information of a corresponding pixel of the second region on the transparency information of that source pixel, including performing a geometric transformation such that at least one dimension of the second region is less than a corresponding dimension of the first region; and

save the transformed image in a target format not providing native support for transparency.

27. A non-transitory computer-readable medium storing processor-executable instructions that when executed cause a processor to:

superimpose a partially transparent overlay image on a base image, an overlay representation of the overlay image being in a format not providing native support for transparency, the overlay representation including a first region of pixels—whose colour information represents colour information of corresponding pixels of the overlay image—and a second region of pixels—whose colour information represents transparency information of corresponding pixels of the overlay image, by, for each base pixel in the base image:

determining first colour information from the colour information of that base pixel;

determining second colour information from the colour information of at least one corresponding pixel of the first region of the overlay representation;

determining transparency information from the colour information of at least one corresponding pixel of the second region of the overlay representation, including performing a geometric transformation on the second region of the overlay image, wherein at least one dimension of the second region is less than a corresponding dimension of the first region; and

computing colour information for a corresponding pixel of a composited image by combining the first colour information, the second colour information, and the transparency information; and

save the composited image in a format not providing native support for transparency.