Delphi – Populate an imagelist with icons at runtime ‘destroys’ transparency

delphiiconsimagelist

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!

Best Answer

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;

Related Solutions

Delphi – PNGs in Delphi 2009 Imagelists and Images

From my research I found that TImageList stores the images as TBitmaps, so the alpha information is lost on storage, and you can't achieve what you're looking for with the current implementation of TImageList.

Update:

A little more experiments and with the code below i could make transparency work with the code below.

ImageList1.ColorDepth := cd32Bit;
Image2.Transparent := True;
Image2.Canvas.Pen.Style := psClear;
Image2.Canvas.Rectangle(0, 0, Image2.Width+1, Image2.Height+1);
ImageList1.Draw(Image2.Canvas, 0,0,0);

But it didn't look as pretty as a loaded png.

Delphi and 48×48 (or bigger) imagelists – is there a workaround

I'm not aware of any limitation on the size of images that TImageList can hold. It sounds to me that your problem is that you have icons of different sizes and you can't hold icons of different sizes in the same image list.

If you are working with icons of different sizes then you are going to need to grow the smaller ones in size. You'll have to build it up in code, using a bitmap. You fill the bitmap with pure transparent alpha channel and then blt the smaller icon onto the centre of the bitmap.

Another option would be to maintain two separate image lists but if you need to draw the icons into the same list view then I think that won't get the job done. My guess is that you'll need to grow the small icons.

For alpha, you're going to need to create the image list handle yourself because the ColorDepth property doesn't exist in D7. Because of this, a vanilla D7 TImageList simply cannot support icons with alpha channels.

You work around this limitation by calling ImageList_Create, passing ILC_COLOR32 and assigning the result to ImageList.Handle. Do this before you add any images. You'll have to populate the list at run time rather than design time, but it sounds like you are already doing that.

Here's a screen shot of a 48x48 tool button with a 32bpp icon with alpha transparency:

48px icon from image list

It's true that I made this in D2010, but my above workaround will work for D7 – I used that mechanism until quite recently with D6. I'm just showing this to prove that the image list can hold 48px icons. Since TImageList is just a wrapper around the system image list component, I believe what you are attempting should be perfectly feasible.

Best Answer

Related Solutions

Delphi – PNGs in Delphi 2009 Imagelists and Images

Delphi and 48×48 (or bigger) imagelists – is there a workaround

Related Topic