https://www.pauldebevec.com/Research/HDR/PFM/

http://paulbourke.net/dataformats/pbmhdr/

https://stackoverflow.com/questions/30255317/does-anyone-know-how-to-convert-to-little-endian-pfm-file-from-imagemagic

$ convert -size 2x2 xc:red -endian LSB PFM:- | hexdump
$ convert -size 2x2 xc:red -endian MSB PFM:- | hexdump