This is a format for compact font storage in the OpenType system, allowing for the rasterization of text information. It differs from TrueType in its abilities to describe font symbols and with its font structure variation algorithm, depending on the change in size. CFF allows for increased screen clarity with high resolution, but this is not due to the font, but its rasterization.
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.