Delphi - Populate an imagelist with icons at runtime 'destroys' transparency

Question

I've spended hours for this (simple) one and don't find a solution :/

I'm using D7 and the TImageList. The ImageList is assigned to a toolbar. When I populate the ImageList at designtime, the icons (with partial transparency) are looking fine. But I need to populate it at runtime, and when I do this the icons are looking pretty shitty - complete loose of the partial transparency.

I just tried to load the icons from a .res file - with the same result. I've tried third party image lists also without success. I have no clue what I could do :/ Thanks 2 all ;)

edit:

To be honest I dont know exactly whats going on. Alpha blending is the correkt term... Here are 2 screenies:

Icon added at designtime:
_{(source: shs-it.de)}

Icon added at runtime:
_{(source: shs-it.de)}

Your comment that alpha blending is not supported just brought the solution: I've edited the image in an editor and removed the "alpha blended" pixels - and now it looks fine. But its still strange that the icons look other when added at runtime instead of designtime. If you (or somebody else ;) can explain it, I would be happy ;) thanks for you support!

Answer 1

To support alpha transparency, you need to create the image list and populate it at runtime:

function AddIconFromResource(ImageList: TImageList; ResID: Integer): Integer;
var
  Icon: TIcon;
begin
  Icon := TIcon.Create;
  try
    Icon.LoadFromResourceID(HInstance, ResID);
    Result := ImageList.AddIcon(Icon);
  finally
    Icon.Free;
  end;
end;

function AddPngFromResource(ImageList: TImageList; ResID: Integer): Integer;
var
  Png: TPngGraphic;
  ResStream: TStream;
  Bitmap: TBitmap;
begin
  ResStream := nil;
  Png := nil;
  Bitmap := nil;
  try
    ResStream := TResourceStream.CreateFromID(HInstance, ResID, RT_RCDATA);
    Png := TPNGGraphic.Create;
    Png.LoadFromStream(ResStream);
    FreeAndNil(ResStream);
    Bitmap := TBitmap.Create;
    Bitmap.Assign(Png);
    FreeAndNil(Png);
    Result := ImageList.Add(Bitmap, nil);              
  finally
    Bitmap.Free;
    ResStream.Free;
    Png.Free;
  end;
end;

// this could be e.g. in the form's or datamodule's OnCreate event
begin
  // create the imagelist
  ImageList := TImageList.Create(Self);
  ImageList.Name := 'ImageList';
  ImageList.DrawingStyle := dsTransparent;
  ImageList.Handle := ImageList_Create(ImageList.Width, ImageList.Height, ILC_COLOR32 or ILC_MASK, 0, ImageList.AllocBy);
  // populate the imagelist with png images from resources
  AddPngFromResource(ImageList, ...);
  // or icons
  AddIconFromResource(ImageList, ...);

end;