Convert ppm to heic
A browser can't do this one — here is what it can do.
Desktop app only
Nothing that runs in a tab can write heic from ppm. This pair is waiting on the desktop build, which hands the job to the real command-line tools.
Browse what does workAbout PPM
Portable Pixmap
The color member of the Netpbm family: uncompressed RGB pixels after a short text header, in binary or plain-text form. Use it as a simple interchange format for scripts and image tools that read raw pixels.
About HEIC
HEIC (HEVC-coded HEIF image)
HEVC-compressed images in a HEIF container. iPhones have saved photos this way by default since iOS 11 in 2017, at much smaller sizes than JPG, but Windows and many websites cannot open them without extra codecs. Convert HEIC to JPG or PNG to open iPhone photos on Windows, upload them to sites that reject HEIC, or share them.