//This function adds a sepia effect to a bitmap.
//the 'depth' sets the colour intensity of the red-brown colour
//greater numbers set a higher intensity.
//To create a greyscale effect instead, set 'depth' to 0
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;