Transparent PNGs saved incorrectly

[jkorchok]

Describe the bug
PNG icons with transparent areas are often (but not always) saved incorrectly. The transparent areas become black.

To Reproduce
Steps to reproduce the behavior:
In Adobe PhotoShop, edit a PNG icon and use the Save for Web feature. Set a single color as the transparent color and save with a new name. Import that PNG to an Office file using the RibbonX Editor. The icon appears normally. Click on the Save button. Close the file and re-open in the RibbonX Editor or in an Office program. The transparent areas are now black. This happens with about 80% of the icons and is not predictable as to which icons will have the transparent areas recolored.

Expected behavior
Icons should be saved as imported.

Screenshots
See icons circled in red: https://www.brandwares.com/images/PNGSaveBug.png

Additional context
Version 1.9.0.1056, under Windows 10.0.19044

[Eric51284]

FWIW, I discovered that the problematic icons could be fixed by opening them in Photoshop, and changing the Image Mode from "Indexed Color" to "RGB Color".

[jkorchok]

Yes, but then you lose the ability to set a transparent color, which is the reason for saving to indexed color in the first place.

[Eric51284]

My backgrounds have remained transparent