Convert JNG to PGM

The JPEG Network Graphics (JNG) file extension is designed for storing JPEG-encoded image data within the PNG file format. Introduced as part of the MNG (Multiple-image Network Graphics) format, JNG was created to provide a flexible, high-quality image format that supports both lossy and lossless compression. It is particularly useful in applications requiring the integration of JPEG compression within a wider range of data types and multimedia elements. Though not widely adopted, JNG offers enhanced compatibility and versatility for complex imaging tasks in computer graphics and web development.

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.