This file format is used to transmit image data. It contains a set of images that can be linked to form an animation. It is used to store non-compressed bitmap images in 24-bit color created using MTV ray tracer.
A bitmap image in the Portable Any Map format that was originally developed for processing and storing several types of monochrome and color images without compression as well as grayscale images. Bitmap graphics data in a PNM file are stored using ASCII or binary structure.