Paint Box를 투명하게 한다는게 무슨 의미인지...

원래 그려지는 부분을 제외하곤 투명하지 않은가요? (그려지는 부분빼곤 뒤에부분이 잘 보이는데...;)

procedure TForm1.FormPaint(Sender: TObject);
begin
Canvas.StretchDraw(Rect(0, 0, Width, Height), TBitmap(Image1.Picture.Graphic));
PaintBox1.Canvas.Draw(0, 0, TBitmap(Image2.Picture.Graphic));
end;

Paint Box를 투명하게 하는게 아니라 그려진 부분에 알파블렌딩을 적용하시고자 하시는건가요?

그거라면 대충 이렇게...

procedure TForm1.FormPaint(Sender: TObject);
var
ABmp: TBitmap;
bfBlend : _BLENDFUNCTION;
begin
Canvas.StretchDraw(Rect(0, 0, Width, Height), TBitmap(Image1.Picture.Graphic));
ABmp := TBitmap.Create;

with ABmp do
begin
try

PixelFormat := pf24bit;
Width := Image2.Width;
Height := Image2.Height;
Canvas.Draw(0, 0, TBitmap(Image2.Picture.Graphic));

bfBlend.BlendOp := AC_SRC_OVER;
bfBlend.BlendFlags := 0;
bfBlend.SourceConstantAlpha := 80;
bfBlend.AlphaFormat := 0;

Windows.AlphaBlend(PaintBox1.Canvas.Handle, 0, 0, PaintBox1.Width, PaintBox1.Height, Canvas.Handle, 0, 0, Width, Height, bfBlend);

finally
if Assigned( ABmp ) then FreeAndNil( ABmp );
end;
end;

end;