How to extract one single file from a tar.xz file?
This should work:
tar -xf file.tar.xz "/file/to/extract.png"
There are many ways to extract specific or selected files from a tar archive file, but the most used way in Linux using tar options as shown:
tar -tf filename.tar.gz filename
For more examples about tar command can be found at: http://www.tecmint.com/extract-tar-files-to-specific-or-different-directory-in-linux/