Wiki Skia
What the difference between SkImage/SkPicture/SkCanvas/SkSurface?
SkBitmap based SkCanvas very slow... How to improve draw speeds?
How to move SkImage from CPU to GPU?
How to control the SkImage GPU back cache size?
As far as I understand when I load SkImage from file or SkBitmap the SkImage lives in CPU side memory. Then the moment I draw this SkImage on a GPU backed canvas it will make a copy of the CPU data into a GPU backed texture. So now we technically have two copies available on the SkImage. Then each time I draw that SkImage it will do it quickly cause it's already in the GPU side.