If you paste the captured screenshot from clipman, a degraded png image will be pasted
Maybe it's related to the clipboard plugin, but I haven't found anything in the code there that can save a fake png. If you save the image to disk, it will save a png file, always. Copying to the clipboard sometimes results in a fake png and I don't understand what causes this.
┌(monsterovich@pc)─(pts/1)─(~/.cache/xfce4/clipman)
└─(>) mediainfo image0.png
General
Complete name : image0.png
Format : PNG
Format/Info : Portable Network Graphic
File size : 677 KiB
Image
Format : PNG
Format/Info : Portable Network Graphic
Format_Compression : LZ77
Width : 878 pixels
Height : 817 pixels
Bit depth : 24 bits
Compression mode : Lossless
Stream size : 677 KiB (100%)
mediainfo says it's a png but...
there are jpg artifacts in the image
if the file is saved to disk, it looks ok
xfce4-screenshooter --version
xfce4-screenshooter 1.9.8
If you use the flameshot app instead, copying to the clipboard always produces a normal image.