1:
2:
3:
4:
5:
6:
7:
8:
9:
10:
11:
12:
13:
14:
15:
16:
17:
18:
19:
20:
21:
22:
23:
24:
25:
26:
27:
28:
29:
30:
31:
32:
33:
34:
35:

procedure TForm1.Save(const AFileName: String);
var
  imgPng: TPngObject;
  PixelPtr: PColor32;
  AlphaPtr: PByte;
  X, Y: Integer;
begin
  imgPng := TPngObject.Create;
  try
    // Bitmap32 in PNG laden
    imgPng.AssignHandle(FBitmap32.BitmapHandle, False, 0);

    // Ggf. Alpha-Kanal von Bitmap32 nach PNG uebertragen
    if FBitmap32.HasAlpha then
    begin
      imgPng.CreateAlpha;
      PixelPtr := PColor32(@FBitmap32.Bits[0]);
      for Y := 0 to FBitmap32.Height - 1 do
      begin
        AlphaPtr := PByte(imgPng.AlphaScanline[Y]);
        for X := 0 to FBitmap32.Width - 1 do
        begin
          AlphaPtr^ := PixelPtr^ shr 24;
          Inc(PixelPtr);
          Inc(AlphaPtr);
        end;
      end;
    end;

    // PNG-Datei speichern
    imgPng.SaveToFile(AFileName);
  finally
    imgPng.Free;
  end;
end;					

1:
2:
3:
4:
5:
6:
7:
8:
9:
10:
11:
12:
13:
14:
15:
16:
17:
18:
19:
20:
21:
22:
23:
24:
25:
26:
27:
28:
29:
30:
31:
32:
33:
34:
35:
36:
37:
38:
39:
40:
41:
42:
43:
44:
45:
46:
47:

procedure TForm1.Load(const AFileName: String);
var
  pictImage: TPicture;
begin
  pictImage := TPicture.Create;
  try
    // Image laden
    pictImage.LoadFromFile(AFileName);

    // Image in Bitmap32 laden
    FBitmap32.Clear;
    FBitmap32.Assign(pictImage);

    // DrawMode zuruecksetzen
    FBitmap32.DrawMode := dmOpaque;
    FBitmap32.OuterColor := clNone;
    FBitmap32.HasAlpha := False;

    // DrawMode abhaengig von Image-Format und Transparenz/Alpha setzen
    if (pictImage.Graphic is TGraphicExGraphic) then
      with TGraphicExGraphic(pictImage.Graphic) do
      begin
        if ImageProperties.HasAlpha then
        begin
          FBitmap32.HasAlpha := True;
          FBitmap32.DrawMode := dmBlend;
        end
        else
        begin
          FBitmap32.DrawMode := dmTransparent;
          if (pictImage.Graphic is TPNGGraphic) then
            with TPNGGraphic(pictImage.Graphic) do
              FBitmap32.OuterColor := Color32(TransparentColor);
        end;

        if (pictImage.Graphic is TGIFGraphic) then
          with TGIFGraphic(pictImage.Graphic) do
            if Transparent then
            begin
              FBitmap32.DrawMode := dmBlend;
              FBitmap32.OuterColor := TGIFGraphic(pictImage.Graphic).TransparentColor;
            end;
      end;
  finally
    pictImage.Free;
  end;
end;					

1:
2:
3:
4:
5:
6:
7:
8:

TMyBitmap32 = class(TBitmap32)
  private
    FHasAlpha: Boolean;
  public
    property HasAlpha: Boolean read FHasAlpha write FHasAlpha;
  end;

FBitmap32: TMyBitmap32