而下面的函数导致实质就是画到了Image.Picture.Bitmap上!
function TImage.GetCanvas: TCanvas;
var
Bitmap: TBitmap;
begin
if Picture.Graphic = nil then
begin
Bitmap := TBitmap.Create;
try
Bitmap.Width := Width;
Bitmap.Height := Height;
Picture.Graphic := Bitmap;
finally
Bitmap.Free;
end;
end;
if Picture.Graphic is TBitmap then
Result := TBitmap(Picture.Graphic).Canvas
else
raise EInvalidOperation.Create(SImageCanvasNeedsBitmap);
end;