procedure TForm1.Button1Click(Sender: TObject);
var
Bitmap: TBitmap;
MyRect, MyOther: TRect;
begin
Bitmap := TBitmap.Create;
Bitmap.LoadFromFile('E:/dzcvs/bmp/custom.bmp');
MyRect := Rect(0,0,bitmap.Width,Bitmap.Height);
MyOther := Rect(0,50,bitmap.Width,50+Bitmap.Height);
Form1.Canvas.CopyRect(MyOther,Bitmap.Canvas,MyRect);
Bitmap.Free;
end;