Convert Bitmap to Sephia

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;

//Example:
procedure TForm1.Button1Click(Sender: TObject);
begin
bmptosepia(image1.picture.bitmap, 20);
end;