Allows better platform-agnostic path manipulation.
Also, using `std::optional` rather than empty strings allows
correctly handling empty arguments (treating them as such,
instead of acting as they were never passed).
- Changes most `/* comments */` to `// comments`
- Changes `/**` block comments consistently to `/*`
- Adds consistent license comments to all files
Also renames `T_POP_SET` to `T_Z80_SET`
Not hooked to all RGBGFX flags yet, but good enough for most use cases
(and as a base for future development, should I need to `reset --hard`.)
TODOs marked appropriately.
Currently missing from the old version:
- `-f` ("fixing" the input image to be indexed)
- `-m` (the code for detecting mirrored tiles is missing, but all of the
"plumbing" is otherwise there)
- `-C`
- `-d`
- `-x` (though I need to check the exact functionality the old one has)
- Also the man page is still a draft and needs to be fleshed out
More planned features are not implemented yet either:
- Explicit palette spec
- Better error messages, also error "images"
- Better 8x16 support, as well as other "dedup unit" sizes
- Support for arbitrary number of palettes & colors per palette
- Other output formats (for example, a "full" palette map for "streaming"
use cases like gb-open-world)
- Quantization?
Some things may also be bugged:
- Transparency support
- Tile offsets (not exposed yet)
- Tile counts per bank (not exposed yet)
...and performance remains to be checked.
We need to set up some tests, honestly.
