convert image from RGB to raw data using ImageMagick convert tool:`convert image.png RGB:data`
then, we see content is a ZPAQ archive...  `mv data data.zpaq`  `zpaq -x data.zpaq`
and we'll get a hxp-home ext4 drive. Just try to mount it using mount:  `sudo mkdir -p /mnt/hxp`  `sudo mount -t ext4 -o loop, hxp-home /mnt/hxp`  
then after by greppiing for flag you'll see some records in .viminfo and .bash_history..we can recover content of file using vim:  `cd /mnt/hxp`  `HOME=$PWD`  `sudo vim -c 'normal @q' -c ':wq! flag.txt'`  
then just cat the flag:  `cat flag.txt`   `hxp{piece-of-cake}`  