extract
Sets dst to alpha described by pixels. Returns false if dst cannot be written to or dst pixels cannot be allocated.
Return
true if alpha layer was not constructed in dst PixelRef
Parameters
dst
holds PixelRef to fill with alpha layer
Sets dst to alpha described by pixels. Returns false if dst cannot be written to or dst pixels cannot be allocated.
If paint is not null and contains MaskFilter, MaskFilter generates mask alpha from Bitmap. Returns offset to top-left position for dst for alignment with Bitmap; (0, 0) unless MaskFilter generates mask.
Return
null if alpha layer was not constructed in dst PixelRef, IPoint otherwise
Parameters
dst
holds PixelRef to fill with alpha layer
paint
holds optional MaskFilter; may be null