This is a companion document to the Naïve Image Formats (NIE, NII, NIA) Specification. Its contents aren't necessary for implementing the NIE file format, but gives further context on what NIE is and is not.
Amongst uncompressed formats, Farbfeld is a very similar design. The main difference is that NIE is little-endian (the same as the vast majority of CPUs) where Farbfeld is big-endian. NIE/NII/NIA also allows animated images, not just still images, and is also configurable: non-premultiplied versus premultiplied alpha and 8- versus 16-bit channels. Configurability is admittedly a trade-off. One person‘s configuration parameter is another person’s unnecessary bloat. We're not saying that Farbfeld is a bad design, just a different design that has chosen different trade-offs.
PAM (Portable Arbitrary Map) and its related formats (PBM, PGM, PPM) are also very similar. The main difference is that their headers are ASCII text and of variable length. Such headers are easier for humans to read but harder for computers to parse. Again, NIE/NII/NIA also allows animated images. Some programs process concatenated streams of PAM images as an animation, but that doesn't contain explicit timing information.
VIPS is the intermediate format for the libvips image processing library. Pixel data is stored in a straightforward fashion, but metadata is stored as XML, which is not simple, and is a potential security concern.
Amongst flexible formats, BMP, PNG and its animated variant APNG, Targa and TIFF all have their built-in compression being optional. Some of those uncompressed forms have been used as simple interchange formats. Compared to those, NIE has fewer features, which is obviously unfavorable if you want such features, but can be favorable if you prefer simplicity and code auditability. A NIE file is still simpler than an uncompressed BMP file and a NIA file is still simpler than an uncompressed APNG file.
For example, when using a sandboxed worker process to convert to an intermediate format, we don‘t want to use “all possible valid TIFF images” as the intermediate format, because a compromised worker process could generate a malicious intermediate image that provoked a security bug in an unsandboxed TIFF decoder. Instead, we would want only a very simple subset of TIFF, but it can be easier (in terms of implementation and in terms of a code audit) to write an (almost trivial) NIE parser from scratch instead of whittling down a full-featured TIFF library and hoping that you’ve eliminated all the potential security vulnerabilities.