Convert atr to pnm Online: atr2pnm

You can use Tom's Editor to easily convert images from
Attributes .ATR to Portable aNy Map .PNM.
Tom's Editor is a free, online image manipulation and converter program.

Go to Tom's Editor

ATR

Attributes is an image format with extension ATR.

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.