Add a png image to a imagelist in runtime using Delphi XE

According to MSDN an imagelist can only contain bitmaps and icons. To add a png image to an imagelist you have to convert it to an icon first. The code to do that can be found in the PngComponents package. If you have only PNG images in your imagelist you can for simplicity just use TPngImageList that comes with that package.

Delphi XE has all the support to handle png images and 32-bit bitmaps with alpha channel. Here is how to add png to an ImageList:

uses CommCtrl;

var pngbmp: TPngImage;
    bmp: TBitmap;
    ImageList: TImageList;
begin
  ImageList:=TImageList.Create(Self);
  ImageList.Masked:=false;
  ImageList.ColorDepth:=cd32bit;
  pngbmp:=TPNGImage.Create;
  pngbmp.LoadFromFile('test.png');
  bmp:=TBitmap.Create;
  pngbmp.AssignTo(bmp);
  // ====================================================
  // Important or else it gets alpha blended into the list! After Assign
  // AlphaFormat is afDefined which is OK if you want to draw 32 bit bmp
  // with alpha blending on a canvas but not OK if you put it into
  // ImageList -- it will be way too dark!
  // ====================================================
  bmp.AlphaFormat:=afIgnored;
  ImageList_Add(ImageList.Handle, bmp.Handle, 0);

You must include

ImgList, PngImage

If you now try:

  Pngbmp.Draw(Bmp1.Canvas,Rect);
and
  ImageList.Draw(Bmp1.Canvas,0,0,0,true);

you'll see that the images are the same. Actually, there are a few \pm 1 rgb differences due to rounding errors during alpha blending but you cannot see them with naked eye. Neglecting to set bmp.AlphaFormat:=afIgnored; would result in the second image being much darker!

Best regards,

alex

• Create an instance of TPngImage, PngImage: PngImage
• Load the image into this instance, PngImage.LoadFromFile(..)
• Create an instance of TBitmap, Bitmap: TBitmap
• Assign the PNG to the bitmap, Bitmap.Assign(PngImage)
• Add the bitmap to the image list
• Job done!