PNG with transparency is not displayed correctly as thumbnail

[Korb]

After adding this file as a thumbnail (option Select an image from gallery):

Instead of a text inscription on some background, the following is displayed:

(screenshot edited to reduce image height, barcode blurred)

View of the loaded image in the graphic editor:

That is, the color of the inscription filled the entire image, making it monochromatic.

Expected Behavior

1. disable loading images with transparency, or
2. allow the user to select a background color for each such image, or
3. After loading the image for the thumbnail, you should always combine this image (top layer) and the solid gray color in the area #4A4A4A..#4C4C4C (bottom layer).
4. After uploading the image for the thumbnail, always overlay it on a gray wallpaper with a mosaic of the Catima logo =)