procedure RgnWindow();

begin

var
  rgn1,rgn2: HRGN;
  x,y,w,h, i: Integer;
begin
w := img1.Width;
h := img1.Height;

rgn1 := CreateRectRgn(0, 0, w, h);

for x := 0 to w - 1 do

begin
  for y := 0 to h - 1 do

  begin
    if img1.Canvas.Pixels[x,y] = clwhite then
    begin
      rgn2 := CreateRectRgn(x, y, x+1, y+1);
      CombineRgn(rgn1, rgn1, rgn2, RGN_XOR);
      DeleteObject(rgn2);
    end;

  end;

end;
SetWindowRgn(Handle, rgn1, True);

Self.Width := w;
Self.Height := h;

end;

Img1为TImage控件。

根据图片的形状建立窗口。