Convert pgm to heif
A browser can't do this one — here is what it can do.
Desktop app only
Nothing that runs in a tab can write heif from pgm. This pair is waiting on the desktop build, which hands the job to the real command-line tools.
Browse what does workAbout PGM
Portable Graymap
The grayscale member of the Netpbm family: uncompressed pixels after a short text header. Use it to feed grayscale images to computer vision and image-processing code that reads Netpbm.
About HEIF
High Efficiency Image File Format
An MPEG container standard (ISO/IEC 23008-12) from 2015 for single images and image sequences. It can hold HEVC, AV1 or other codecs, along with depth maps and bursts. Convert HEIF to JPG or PNG for apps and sites that cannot read it.