Convert cpt to pnm Online: cpt2pnm

You can use Tom's Editor to easily convert images from
Canvas (compressed) .CPT to Portable aNy Map .PNM.
Tom's Editor is a free, online image manipulation and converter program.

Go to Tom's Editor

CPT

Canvas (compressed) is an image format with extension CPT.

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.