procedure TForm1.FormPaint(Sender: TObject);
var
I: Word ;
Y,YStep: Real;
begin
Y:=0; // 设置Y方向的初
YStep:=ClientHeight/256; // 设置步长
for I:=255 downto 0 do
begin
Canvas.Brush.Color:=$00000000+i*$10000; // 改变颜色
Canvas.FillRect(Rect(0,Round(Y),ClientWidth,Round(Y+YStep)));
Y:=Y+YStep;
end;
end;