Convert SIXEL to PGM

The SIXEL, or "six pixels", is a bitmap graphics format created by Digital Equipment Corporation (DEC) for their terminals and printers. Initially designed for DEC dot matrix printers like the LA50, it enabled the efficient transfer of bitmap graphics using a series of ASCII characters. Each character represents a 6-pixel high row, making it suitable for 7-bit serial communication. This format was later adapted for modern terminal emulators, extending its utility beyond its original scope.

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.