Convert OTB to PGM

The OTB (Over The Air Bitmap) file extension, developed by Nokia, is used for transmitting black and white bitmap images between mobile phones, particularly Nokia and Siemens models. These images, with a maximum resolution of 255x255 pixels, are often sent via SMS in either hexadecimal text or binary format. Historically, OTB files were popular in the early days of mobile communication for sending simple graphics, icons, and wallpapers when data transmission speeds were limited.

The Portable Graymap (PGM) file extension, originating in the late 1980s as part of the Netpbm project, stands for "Portable Gray Map". It serves as a simple, versatile format for grayscale images, enabling easy reading and writing by various programs. Due to its straightforward structure and plain text encoding, it's often used in academic and research settings where ease of parsing and accessibility are crucial. PGM files store grayscale images in a compact, efficient manner, making them an essential tool for image processing tasks.