Convert jpeg to pnm Online: jpeg2pnm

You can use Tom's Editor to easily convert images from
Joint Photographic Experts Group JFIF .JPEG to Portable aNy Map .PNM.
Tom's Editor is a free, online image manipulation and converter program.

Go to Tom's Editor

JPEG

The most popular image format. Does not support Alpha channel. Images are always lossy coded so when an image is saved as JPEG it always looses a bit of quality.

PNM

PNM images are uncompressed 24 bit RGB images. Can cannot store Alpha channel. PNM images come in 2 types: binary and text. Especially popular on Linux.