Apply a feathering effect to the image. Feathering softens the edges of an image by applying alpha transparency at a rate that is proportional to the distance to the edge (specifically, adding a gradient in the alpha channel).
FeatherDepth specifies the depth in pixels of the feather effect. The range is 0 to 255, with typical values of 2 to 5. If iFeatherDepth = 0 then the image is not feathered but a simple smoothing filter is applied to reduce the jagged edges of the image.
Note: Method has no effect if the image does not have an alpha channel