Convert pgm to icb

What is the difference between .pgm and .icb?

Description: 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.; The ICB file format, standing for Targa ICB Bitmap Image, is a type of image file associated with the Targa (Truevision Advanced Raster Graphics Adapter) image format. Targa files, including ICB, are known for their versatility in handling various types of digital images, including color, grayscale, and monochrome. The ICB variant is part of a broader family of Targa formats, which are often used in professional environments for digital video editing, animation, and graphic design.