Please run the attached standalone example which:

1. Creates a square with a transparent square in the middle.
2. Saves this ("output.png")
3. Loads this image into the clipboard.

If we inspect the saved image we can see it is a PNG with transparency. However, when loading it into the clipboard the clipboard history shows the transparent section as black.

Pasting is problematic, some applications are able to paste the image with the correct transparency but most fill it with black.

Works: MS Paint

Doesn't work: MS office suite (word, powerpoint, excel)