Convert xwd to pgm

What is the difference between .xwd and .pgm?

Description: The XWD (X Windows Dump) image file format is a native graphic format associated with the X Window System, which is a windowing system for bitmap displays commonly used in UNIX and Linux environments. An XWD file is essentially a dump or snapshot of what is being displayed on a screen or part of it at a given moment. It stores image data in an uncompressed form, including the header information that contains details about the image's size, color, and format.; A PGM file is a grayscale image file saved in the portable gray map (PGM) format and encoded with one or two bytes (8 or 16 bits) per pixel. It contains header information and a grid of numbers that represent different shades of gray from black (0) to white (up to 65,536). PGM files are typically stored in ASCII text format, but also have a binary representation.