This format is used for storing several types of bitmaps, including animations. MNG allows you to store lossy and lossless images with compression. This format provides you with more options than GIF for saving animated files while keeping the original image size.
PGM is a storage format for grayscale images. Files in this format can be opened using software: ACDSee Photo Manager 14, ACD Systems Canvas 15, Corel PaintShop Pro X4. This type of file can be edited with a text editor. PGM files can be in two versions: P2 / P5. P2 are readable, P5 - to binary formats.