dcraw is an ANSI C program that decodes any raw image from any digital camera
on any computer running any operating system. It's become a standard tool
within and without the Open Source world. It's small (about 3000 lines),
portable (standard C libraries only), free (both "gratis" and "libre"), and
when used skillfully, produces better-quality output than the tools provided by
the camera vendor.

WWW: https://www.dechifro.org/dcraw/