Apple Inc.
Layered image compression

Abstract:

Disclosed are techniques for pre-processing layered images prior to compression and distribution. According to some embodiments, a technique can include accessing at least two images of a layered image: (i) a background image, and (ii) one or more layer images. Next, a flattened image is generated based on the at least two images. Next, respective one or more delta layer images are generated for the one or more layer images by: for at least one pixel of each layer image having (i) an alpha sub-pixel set to fully opaque, and (ii) a first color property equivalent to a second color property of a corresponding pixel within the flattened image: setting bits of the first color property of the pixel to the same value (e.g., zero (0) or one (1)). Finally, the one or more delta layer images are compressed and provided to a destination computing device.