Add find_convex_hull using Graham scan

[arrufat]

So, I know I've not been very active on dlib really...
The thing is, at my current job I am using Zig quite a bit, and therefore, not using dlib as much as I'd like.

However, today I had to compute the convex hull of a set of points at work and checked if an implementation on dlib existed to port it to Zig, but I couldn't find it.

So I coded it in Zig, and now I am back porting it to dlib, as I think it may be useful.

Let me know if you think the stuff in the impl namespace should also be exposed to the users.

[pfeatherstone]

Interesting companies are already using Zig even though it hasn't reached 1.0 yet. Do you find there are enough libraries in the Zig ecosystem to be productive ? I'm genuinely interested. I quite like the look of it, but don't fancy rewriting the world.

[arrufat]

@pfeatherstone, well, I did have to rewrite the world, basically. We built a virtual try on for makeup that runs completely on the browser using WebAssembly.
First, I made a version in C++ and Emscripten.
I was using dlib, of course, but there are some functions that implicitly allocate, and couldn't be used for WebAssembly directly. At least I didn't know how to, without modifying them.

Eventually, we got interested in Zig because it has native support for Wasm, and all functions that allocate take an allocator as a parameter. So it's easy to just allocate a bunch of memory from JavaScript, pass it to Zig and create a fixed buffer allocator, and use that as a memory pool. But I had to write everything (some PRs made it into dlib from the C++ version):

• color space conversions (Add HSV support #2758)
• blurring and cropping images
• functions for drawing lines and filling polygons (Add draw solid polygon #2775)
• projective transforms (including an SVD... That was fun)
• a matrix class that doesn't allocate memory
• and of course, convex hull (Add find_convex_hull using Graham scan #2889)

It's a nice little language, though.

This reminds me of this Tweet:

Use a library? No. I didn't pick C++ so someone else can just go and do all of the fun stuff.

— Ólafur Waage (@olafurw) April 22, 2023

[pfeatherstone]

Great work! I still think I'll only start paying attention to Zig when there is something like onnxruntime and a good tasking system. Though it looks like Zig supports coroutines so on the latter point, it seems like that's on its way. In general, these days I hate not being productive. So I'm using Python a lot more and if you use it correctly, the performance gap between Python and C can be quite small. And there is a library for anything possibly imaginable in Python. I basically only use C++ for systems programming now.

[davisking]

Yeah, this is cool :)

[davisking]

And the impl namespace stuff is fine as is :)

[arrufat]

Yes, much nicer, thank you!

[davisking]

Thanks, this is great :)