delphi JPG或BMP图片透明显示

procedure SaveBmpAsIcon(const Bmp: TBitmap; const Icon: string; const SmallIcon: Boolean;
const Transparent: Boolean; const X, Y: Integer);
//  Bmp        : Bitmap图片
//  Icon      : 最终输出的icon文件全路径和文件名。如果文件已经存在则会将其覆盖
//  SmallIcon  : True: 16x16 图标, False: 32x32 图标
//  Transparent: 确定是否按照参数X,Y的坐标色生成透明图标
//  X, Y      : 此参数指明坐标下的色值将会作为透明色替换全图
var
  PBI, MPBI: PBitmapInfo;
  IHS, MIHS, ImageSize, MImageSize: DWord;
  bmBuffer, MaskBuffer: Pointer;
  TID: TIconDir;
  TBIH: TBitmapInfoHeader;
  Bmx, Bmm: TBitmap;
  TranspCol: TColor;
  I, J: Integer;
begin
  Bmx:= TBitmap.Create;
  Bmm:= TBitmap.Create;
  try
    if SmallIcon then
    begin
      Bmx.Width:= GetSystemMetrics(SM_CXSMICON);
      Bmx.Height:= GetSystemMetrics(SM_CYSMICON);
    end
    else
    begin
      Bmx.Width:= GetSystemMetrics(SM_CXICON);
      Bmx.Height:= GetSystemMetrics(SM_CYICON);
    end;
    bmx.pixelformat:=pf24bit;
    Bmx.Canvas.StretchDraw(Rect(, , Bmx.Width, Bmx.Height), Bmp);
    TranspCol:= Bmx.Canvas.Pixels[X, Y];
    //TranspCol:= clWhite;
    Bmm.Assign(Bmx);
    Bmm.Mask(TranspCol);
    GetDIBSizes(Bmm.Handle, MIHS, MImageSize);
    GetDIBSizes(Bmx.Handle, IHS, ImageSize);
    MaskBuffer:= AllocMem(MImageSize);
    bmBuffer:= AllocMem(ImageSize);
    MPBI:= AllocMem(MIHS);
    PBI:= AllocMem(IHS);
    try
      if Transparent then
      begin
        for I:= to Bmx.Width- do
          for J:= to Bmx.Height- do
            if Bmx.Canvas.Pixels[I, J] = TranspCol then Bmx.Canvas.Pixels[I, J]:= ;
        with MPBI^.bmiHeader do
        begin
          biSize:= SizeOf(TBitmapInfoHeader);
          biWidth:= Bmm.Width;
          biHeight:= Bmm.Height;
          biPlanes:= ;
          biBitCount:= ;
          biCompression:= BI_RGB;
          biSizeImage:= MImageSize;
          biXPelsPerMeter:= ;
          biYPelsPerMeter:= ;
          biClrUsed:= ;
          biClrImportant:= ;
        end;
        GetDIBits(Bmm.Canvas.Handle, Bmm.Handle, , Bmm.height, MaskBuffer, MPBI^, DIB_RGB_COLORS);
      end;
      with PBI^.bmiHeader do
      begin
        biSize:= SizeOf(TBitmapInfoHeader);
        biWidth:= Bmx.Width;
        biHeight:= Bmx.Height;
        biPlanes:= ;
        biBitCount:= ;
        biCompression:= BI_RGB;
        biSizeImage:= ImageSize;
        biXPelsPerMeter:= ;
        biYPelsPerMeter:= ;
        biClrUsed:= ;
        biClrImportant:= ;
      end;
      GetDIBits(Bmx.Canvas.Handle, Bmx.Handle, , Bmx.Height, bmBuffer, PBI^, DIB_RGB_COLORS);
      with TBIH do
      begin
        biSize:= ;
        biWidth:= Bmx.Width;
        biHeight:= Bmx.Height * ;
        biPlanes:= ;
        biBitCount:= ;
        biCompression:= ;
        biSizeImage:= ImageSize;
        biXPelsPerMeter:= ;
        biYPelsPerMeter:= ;
        biClrUsed:= ;
        biClrImportant:= ;
      end;
      with TID do
      begin
        idReserved:=;
        idType:=;
        idCount:=;
        with idEntries[] do
        begin
          bWidth:=bmx.width;
          bHeight:=bmx.height;
          bColorCount:=;
          bReserved:=;
          wPlanes:=;
          wBitCount:=;
          dwBytesInRes:= SizeOf(TBitmapInfoHeader) + TBIH.biSizeImage + MImageSize;
          dwImageOffset:=  + TID.idCount * SizeOf(TIconDirEntry);
        end;
      end;
      with TFileStream.Create(Icon, fmCreate) do
      try
        Write(TID,  + TID.idCount * SizeOf(TIconDirEntry));
        Write(TBIH, SizeOf(TBitmapInfoheader));
        Write(bmBuffer^, TBIH.biSizeImage);
        Write(maskBuffer^, MImageSize);
      finally
        Free;
      end;
    finally
      FreeMem(MaskBuffer);
      FreeMem(bmBuffer);
      FreeMem(MPBI);
      FreeMem(PBI);
    end;
  finally
    Bmx.free;
    Bmm.free;
  end;
end;