MNG is an image file category format. It supports all possible PNG and JPEG compression algorithms (including gamma correction and translucency) in order to create animated images. It was available in the Mozilla browser from 2000 to 2003. Now supported by Konqueror browser. MNG, i.e. Multiple-image Network Graphics, has the closest connection with PNG. In 1995, when they started developing the PNG format, it was decided not to include animation support. For a simple reason: then this feature was used infrequently. And yet, we started working on MNG, that is, the version of PNG that supports animation. The initial version of the MNG specification was born in early 2001. The MNG format is a simplified raster analogue of Adobe Flash. Each frame has many layers, and they can be moved relative to each other, scaled, cropped. This explains the complexity of supporting the MNG format. As a result, the MNG file structure resembles the PNG structure. The only difference is the identification tag. And also that much more options of blocks (chunk) are applied. MNG frames are saved as PNG or JNG. Compared to GIF, this format supports animation. Compared to JPEG, it provides the smallest file size due to compression loss. Compared to PNG, compression is done without distortion. Now MNG is not supported by popular browsers and software, since it was replaced by a simpler APNG format.
PNM is a raster image category format. This is a bitmap bitmap created in Portable Any Map format. As you know, this format was intended from the very beginning to process some types of portable monochrome black and white images (PBM), color images (PPM) and grayscale images with shades of gray (PGM). Allows the inclusion of raster graphics data in the .PBM, .PGM or .PPM format. Such formats can provide an intermediate representation of data during the conversion of raster graphic files by different platforms. Separate applications support these three formats directly because they are defined as the PNM format. Able to be stored using binary data or ASCII text. PNM is the common format for the Netpbm package. It contains intermediate files that are used when it comes to converting several open source programs called Portable Bitmap. The PPM format was developed by J. Poskanzer. This is the easiest format for storing graphics. PNM files store one image. They do not apply compression. To view and process a bitmap image in PNM format, you can use programs such as GIMP, ImageMagick, Newera Graphics Converter Pro, XnViewMP. The same programs are able to convert images of this format.