TImage.Picture.Icon Verständisfrage

[Bummi]

versuchs mal damit ....

Delphi-Quellcode:

Procedure LoadPNGAsIcon(const fn: String; var ICO: TIcon);
var
  Header: PBitmapV5Header;
  hNewBitmap, hMonoBitmap: HBITMAP;
  Bits: Pointer;
  x, y: Integer;
  DC: HDC;
  IconInfo: _ICONINFO;
  Pixel: ^Integer;
  ScanLine: PRGBTriple;
  AlphaScanline: pByteArray;
  PNG: TPngObject;
begin

  PNG := TPngObject.Create;
  try
    PNG.LoadFromFile(fn);
    if not Assigned(ICO) then
      ICO := TIcon.Create;
    New(Header);
    FillMemory(Header, SizeOf(BitmapV5Header), 1);
    Header.bV5Size := SizeOf(BitmapV5Header);
    Header.bV5Width := PNG.Width;
    Header.bV5Height := -PNG.Height;
    Header.bV5Planes := 1;
    Header.bV5BitCount := 32;
    Header.bV5Compression := BI_BITFIELDS;
    Header.bV5RedMask := $00FF0000;
    Header.bV5GreenMask := $0000FF00;
    Header.bV5BlueMask := $000000FF;
    Header.bV5AlphaMask := $FF000000;
    DC := GetDC(0);
    hNewBitmap := CreateDIBSection(DC, PBitmapInfo(Header)^, DIB_RGB_COLORS,
      Bits, 0, 0);
    Dispose(Header);
    ReleaseDC(0, DC);
    hMonoBitmap := CreateBitmap(PNG.Width, PNG.Height, 1, 1, nil);
    Pixel := Bits;
    for y := 0 to PNG.Height - 1 do
    begin
      ScanLine := PNG.ScanLine[y];
      AlphaScanline := PNG.AlphaScanline[y];
      for x := 0 to PNG.Width - 1 do
      begin
        if Assigned(AlphaScanline) then
          Pixel^ := AlphaScanline[x]
        else
          Pixel^ := 255;
        Pixel^ := Pixel^ shl 8;
        Inc(Pixel^, ScanLine^.rgbtRed);
        Pixel^ := Pixel^ shl 8;
        Inc(Pixel^, ScanLine^.rgbtGreen);
        Pixel^ := Pixel^ shl 8;
        Inc(Pixel^, ScanLine^.rgbtBlue);
        Inc(Pixel);
        Inc(ScanLine);
      end;
    end;
    IconInfo.fIcon := true;
    IconInfo.hbmMask := hMonoBitmap;
    IconInfo.hbmColor := hNewBitmap;
    ICO.Handle := CreateIconIndirect(IconInfo);

    DeleteObject(hNewBitmap);
    DeleteObject(hMonoBitmap);
  finally
    PNG.Free;
  end;
end;

procedure TForm1.Button1Click(Sender: TObject);
var
  ICO:TIcon;
begin
  ICO := nil;
  LoadPNGAsIcon('C:\Bilder\about.png',ico);
  image1.Picture.Assign(ico);
  ico.Free;
end;