Set the transparency for the selected region. Either setting the alpha channel to a single value, or graduating from one value to another (gradient transparency).
0 is transparent, 255 is opaque, 1 - 254 are partially transparent.
Note: To perform a flood alpha fill, use CastAlpha
// Set selection as fully transparent ImageEnView1.Proc.AlphaFill( 0 );
// Set selection as fully opaque ImageEnView1.Proc.AlphaFill( 255 );
// Set selection as 50% transparent ImageEnView1.Proc.AlphaFill( 128 );
// Graduate the transparency from fully transparent on the top to fully opaque on the bottom ImageEnView1.Proc.AlphaFill( 0, 255, gdVertical );
// Gradient fill the alpha channel with fully transparent on the left to fully opaque on the right ImageEnView1.Proc.AlphaFill( 0, 255, gdHorizontal );