Remove all build-time header generation

[cary-ilm]

Add toFloat.h, eLut.h, b44ExpLogTable.h, dwaLookups.h as first-class headers, and remove the associated cmake/autoconf build rules.

Also:

• add tests in HalfTest and IlmImfTest to validate that the internal tables have the proper values (using
  code from the generation programs)
• move the dwaLookups symbols to the OPENEXR_IMF_INTERNAL_NAMESPACE. They were in the
  global namespace.
  -The original generation program code is still in the repo, although it's no longer compiled or used.

The rationale behind this is to simplify the build process, as the header generation is a frequent source of problems for users building the library, at the cost of disk space. At 6258948 bytes, dwaLookups.h is now the single largest file in the project repo, although it's only 13% of the total repo size, only about twice the size of several of the included test .exr images, so not onerously large.

The original idea discussed in the TSC was to retain make targets to generate the headers, but after considering it further, it seems more appropriate to just do the validation with code inside the test projects. This removes all the complexity of building the generation programs from the Makefiles once and for all, rather than just moving the complexity into the test project Makefiles.

[meshula]

Thanks Cary!

[kdt3rd]

Looks fine mostly, although shouldn't we leave the targets to build the generate programs? If you want, you can add an EXCLUDE_FROM_ALL tag to the add_executable calls

[cary-ilm]

My preference would be to remove the generator code altogether, decrease the entropy of the project. Or leave it as a comment, although if we did ever need it, it’s in the git history. It’s not like we’re ever going to change it. The half table generation is quite simple. The DWA look generation is quite complex because it’s multithreaded.

On Wed, Nov 6, 2019 at 12:36 AM Kimball Thurston ***@***.***> wrote: Looks fine mostly, although shouldn't we leave the targets to build the generate programs? If you want, you can add an EXCLUDE_FROM_ALL tag to the add_executable calls — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub <#606>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AFC3DGPC5PFNOCRRNOYMJZ3QSJ62LANCNFSM4JIIQQXA> .

-- Cary Phillips | R&D Supervisor | ILM | San Francisco

[axxel]

Since the space occupied by the headers was discussed: they are obviously not meant for human consumption. So a substantial amount of space could be saved by choosing a different layout:

• remove all whitespace inside the arrays
• use plain ints instead of hex literals

[cary-ilm]

I experimented with reducing the whitespace, and the files got smaller, but not by enough to justify disturbing the code. There is definitely bloat here, as some of these could be generated efficiently at runtime, but I don't think space concerns are significant.