Градиентная заливка формы

procedure TForm1.GradientRect (FromRGB, ToRGB: TColor; Canvas: TCanvas);
var
RGBFrom : array[0..2] of Byte; { from RGB values }
RGBDiff : array[0..2] of integer; { difference of from/to RGB values }
ColorBand : TRect; { color band rectangular coordinates }
I : Integer; { color band index }
R : Byte; { a color band's R value }
G : Byte; { a color band's G value }
B : Byte; { a color band's B value }
begin
{ extract from RGB values}
RGBFrom[0] := GetRValue (ColorToRGB (FromRGB));
RGBFrom[1] := GetGValue (ColorToRGB (FromRGB));
RGBFrom[2] := GetBValue (ColorToRGB (FromRGB));
{ calculate difference of from and to RGB values}
RGBDiff[0] := GetRValue (ColorToRGB (ToRGB)) - RGBFrom[0];
RGBDiff[1] := GetGValue (ColorToRGB (ToRGB)) - RGBFrom[1];
RGBDiff[2] := GetBValue (ColorToRGB (ToRGB)) - RGBFrom[2];
{ set pen sytle and mode}
Canvas.Pen.Style := psSolid;
Canvas.Pen.Mode := pmCopy;
{ set color band's left and right coordinates}
ColorBand.Left := 0;
ColorBand.Right:= canvas.ClipRect.Right-Canvas.ClipRect.Left;
for I := 0 to $ff do
begin
{ calculate color band's top and bottom coordinates}
ColorBand.Top := MulDiv (I , canvas.ClipRect.Bottom-Canvas.ClipRect.Top, $100);
ColorBand.Bottom := MulDiv (I + 1,canvas.ClipRect.Bottom-Canvas.ClipRect.Top, $100);
{ calculate color band color}
R := RGBFrom[0] + MulDiv (I, RGBDiff[0], $ff);
G := RGBFrom[1] + MulDiv (I, RGBDiff[1], $ff);
B := RGBFrom[2] + MulDiv (I, RGBDiff[2], $ff);
{ select brush and paint color band}
Canvas.Brush.Color := RGB (R, G, B);
Canvas.FillRect (ColorBand);
end;
end;

public
{ Public declarations }
procedure GradientRect(FromRGB, ToRGB: TColor; Canvas: TCanvas);

GradientRect (clBlue, clBlack, Canvas);

Paint;