XnView Software

I use the heic extension from Microsoft Store and saved some files to heic format.
After the conversion I recognized, that XnViewMP saved a few of the pictures with black lines. (Example file attached).

I am not sure, if it is a problem of XnViewMP or the heic extension from Microsoft store.

First I though the program has a problem with the big picture size (longest side >2.000 pixels).
Then I tested it again and saw, that only big files with a odd wide or length have the black lines.
I resized the picture again to a small size (800x599 pixels) and everything is fine.

Very strange!

always at the bottom? do you have tried Paint.net, i think that it use same plugin?

If one side has an odd pixel size, only one side has black lines. If both sides have an odd pixel size, both sides have black lines.
I tested the same problem with Paint.net and I got the same problems with black lines.
The bug is in the HEIC extension. In Microsoft Store I did not find a way to contact Microsoft. It is very complicated to contact them, because they show you a FAQ without useless informations.