I state that all the operations I do with Photoshop.
I'll upload the files you requested and as specific as I did them:

The"A" image is made with an 8-bit black background with the PNG icons inserted and then saved in PNG, it became 32-bit.
The "NNG from A" image is the converted "A" image with your program.
Probably if instead of saving "A" in PNG, save it in 24 bit BMP, everything will be OK, but I will try this in the next days.

The "B" image is the one that crashes your program, is made with an 16-bit black background, later I made transparent black with magic rubber, I inserted the PNG icons and then saved in PNG too, but this image became 64-bit, surely this is the reason that makes your program crash.

The "C" image is made with an 8-bit black background, later I made transparent black with magic rubber, I inserted the PNG icons and then saved in PNG. This image became 32-bit.

The "NNG from C" image is the converted "C" image with your program, I tried this image and it's OK.

As I said before I will do other tests in the next days ......

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