If the layer has an alpha channel then edges of the image will be "feathered." 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).
The value (0 to 255) indicates the depth in pixels of the feather effect.
Note: Feathering is not rendered onscreen at zoom levels above 500% to prevent performance issues
// Apply alpha edge feathering to all selected layers for i := 0 to ImageEnView1.LayersCount - 1 do if ImageEnView1.Layers[ I ].Selected then ImageEnView1.Layers[ I ].AlphaEdgeFeathering := 5; ImageEnView1.Update();