Рисование на картинке мышью

procedure TForm1.Image1MouseDown(Sender: TObject; Button: TMouseButton;
  Shift: TShiftState; X, Y: Integer);
begin
  with Image1.Canvas do begin
   Pen.Color:= clNavy;
   Pen.Width:= 10;
   MoveTo(X, Y);
 end;
end;

procedure TForm1.Image1MouseMove(Sender: TObject; Shift: TShiftState; X,
  Y: Integer);
begin
  if ssLeft in Shift then Image1.Canvas.LineTo(X, Y);
end;

procedure TForm1.Image2MouseMove(Sender: TObject; Shift: TShiftState; X,
  Y: Integer);
var xx,yy:real;
    a,b :real;
begin
     if Shift = [ssRight] then
          begin
             a:= ((Form1.Image2.Picture.Width)/Form1.Image2.Width);
             b:= ((Form1.Image2.Picture.Height)/Form1.Image2.Height);

            if a<=b then
            begin
                  xx:= x*b;
                  yy:= y*b;
            end else
            begin
                  xx:= x*a;
                  yy:= y*a;

            end;

          Image2.Canvas.Pen.Color:=clRed;
          Image2.Canvas.Pen.Width:=8;
           Image2.Picture.Bitmap.Canvas.MoveTo(Trunc(xx),Trunc(yy));
           Image2.Picture.Bitmap.Canvas.LineTo(Trunc(xx),Trunc(yy));
     end;
end;