我想要在 Form 的底圖上蓋一張圖檔(不規則形狀,當按鈕),    看了站上的文章有蠻多方法的, 我現在使用 Graphics32 這個元件, 他的說明中, set the DrawMode to dmBlend and call Draw or DrawTo to blend it to a background bitmap 這段我看不太懂, DrawMode to dmBlend 我了解, 不過 call Draw or DrawTo to blend, 是指要將他的 CromaKey 程式碼放在哪邊呢?    請指教,謝謝.        Q: How do I draw the bitmap with standard color key transparency?    A: Currently Graphics32 does not support color key transparency, but it is possible to preprocess the source bitmap and set its alpha buffer according to the "transparent" color:    

procedure CromaKey(ABitmap: TBitmap32; TrColor: TColor32);
var
  P: PColor32;
  C: TColor32;
  I: Integer;
begin
  TrColor := TrColor and $00FFFFFF; // erase alpha, (just in case it has some)
  with ABitmap do
  begin
    P := PixelPtr[0, 0];
    for I := 0 to Width * Height - 1 do
    begin
      C := P^ and $00FFFFFF; // get RGB without alpha
      if C = TrColor then // is this pixel "transparent"?
        P^ := C; // write RGB with "transparent" alpha back into the SrcBitmap
      Inc(P); // proceed to the next pixel
    end;
  end;
end;

Then, set the DrawMode to dmBlend and call Draw or DrawTo to blend it to a background bitmap. It is possible to use this function several times for different colors