ClientToBitmap example for Delphi

Procedure TForm1.LEADImage1MouseDown(Sender: TObject; Button: TMouseButton;
  Shift: TShiftState; X, Y: Integer);
var
   BitmapX: Integer;
   BitmapY: Integer;
begin
    BitmapX:= x;
    BitmapY:= y;
    LEADImage1.ClientToBitmap ( BitmapX, BitmapY );

    //Change that pixel to White
    LEADImage1.Pixel[LEADImage1.ConvertX, LEADImage1.ConvertY]:= RGB(255, 255, 255 ) ;
end;