Convert bmp to pnm Online: bmp2pnm

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

Go to Tom's Editor

BMP

Format created by Microsoft for their Windows and OS/2 operating systems. Images can be compressed or not.

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.