There is only one file type that uses the .JXR extension:
JPEG XR Image
Image stored in the JPEG XR format, which was originally developed by Microsoft for Windows Media software; supports deep color images with 48-bit RGB; used for high-resolution professional image editing; also supports lossless and lossy compression.
JXR files were designed to support better compression and more color accuracy than .JPG files.
Updated: March 6, 2019