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Some file formats like OBJ and PPM are delightfully simple to write, which makes them great as a debugging tool since you can use an existing viewer, but if you decide to parse them the delight evaporates instantly.
(I guess that's generally true of many file formats? Some formats are painful to read *and* write though!)
@zeux (haha DDS and KTX and then there's KTX2 taking it to the next level)
@zeux that is true for all file formats, yes. OBJ suffers from a vibes-based “spec”, that does not for example even say what is whitespace, what is newline, or what float format is accepted
@zeux most curious OBJ feature: line continuations (“\”), it says it can have them but nowhere it says where they are allowed (in a middle of a number, yes or no? etc). Most parsers blissfully ignore their existence, or crash upon them. Yay!
@aras @zeux That and negative indices I think trip the most people over. But yes, there's a OBJ spec on the internet, except nobody seems to care about the spec, and there's no set of compliance test files to verify you load OBJ right. I wish we'd have an easy way to gather OBJ files generated by program X with feature Y (or any file type, really) to eventually have evidence a parser covers some % of "in the wild" features for those non-standard formats.
@aras @zeux In the end, OBJ parsers become hairballs of bespoke fixes, and the older you are the more likely you win because you saw more different files, which is a terrible situation. And it's not just OBJ - I was writing a TGA loader for the whole format (including scanline table and what not) and turns out no application actually cares about those things/gets them right. We need mandatory format specs/test suites IMHO; otherwise our data will be a hostage of terrible formats forever.
And yes, there is a TGA spec, and it even included a test image suite.@TheIneQuation @aras @zeux Interesting! I know the TGA spec (that's how I knew it supports a scanline table and stuff), where's the image test suite?
@anteru @aras @zeux there was an original package called from Truevision called TGAUTILS that included the TGA 2.0 spec and the images, but it's since disappeared from the internet. The images, however, live on in the OIIO test image repo: https://github.com/AcademySoftwareFoundation/OpenImageIO-images/tree/main/targa
@anteru @aras @zeux there were also code snippets, and they only seem to exist these days on this shady russian website: https://netghost.narod.ru/gff/sample/code/tga/index.htm
@TheIneQuation @anteru @aras Ah, narod.ru strikes back. This was a very popular free web site hosting in Russia circa 2005. Shocked it still works 20 years later.
@zeux if you don’t mind using C++ and Boost.Spirit, an OBJ parser that can read almost every file you can find can be surprisingly succinct 
@w0utert Yes, I do mind.