Krita
From Just Solve the File Format Problem
				
								
				
				
																
				
				
								
				Krita is an open source graphics editor. It has a native layered raster graphics format called .kra or Krita document. The format uses a ZIP container, and appears to be similar to OpenRaster.
Identification
Krita documents are probably supposed to have "mimetypeapplication/x-krita" at offset 30, but we've observed some that lack this signature.
Sample files
- https://github.com/KDE/krita/tree/master/krita/data/templates/ .../*.kra
 - https://telparia.com/fileFormatSamples/image/kra/
 
Links
-  Krita website
- Krita History
 - KRITA Documentation: *.kra - Very minimal information about the .kra format
 
 - Wikipedia: Krita