Bitmap Draw Sepia Effect

uses Jpeg

function bmptosepia(const bmp: TBitmap; depth: Integer): Boolean;
var
color,color2:longint;
r,g,b,rr,gg:byte;
h,w:integer;
begin
  for h := 0 to bmp.height do
  begin
    for w := 0 to bmp.width do
    begin
//first convert the bitmap to greyscale
    color:=colortorgb(bmp.Canvas.pixels[w,h]);
    r:=getrvalue(color);
    g:=getgvalue(color);
    b:=getbvalue(color);
    color2:=(r+g+b) div 3;
    bmp.canvas.Pixels[w,h]:=RGB(color2,color2,color2);
//then convert it to sepia
    color:=colortorgb(bmp.Canvas.pixels[w,h]);
    r:=getrvalue(color);
    g:=getgvalue(color);
    b:=getbvalue(color);
    rr:=r+(depth*2);
    gg:=g+depth;
    if rr <= ((depth*2)-1) then
    rr:=255;
    if gg <= (depth-1) then
    gg:=255;
    bmp.canvas.Pixels[w,h]:=RGB(rr,gg,b);
    end;
  end;
end;

Beispiel :

procedure TForm1.Button1Click(Sender: TObject);
begin
 bmptosepia(image1.picture.bitmap, 10);
end;