4666: {Returns a alpha data scanline}
4667: function TPngObject.GetAlphaScanline(const LineIndex: Integer): pByteArray;
4668: begin
4669:  with Header^ do
4670:    if (ColorType = COLOR_RGBALPHA) or (ColorType = COLOR_GRAYSCALEALPHA) then
4671:      Integer(Result) := Integer(ImageAlpha) + (LineIndex * Longint(Width))
4672:    else Result := nil;  {In case the image does not use alpha information}
4673: end;