LoadEXR/SaveEXR from/to memory

[xelatihy]

Describe the issue
While LoadEXR and SaveEXR are deprecated functionality, they are very useful is one wants to quickly put together applications. This is in the same vein as stb_image. It would be helpful I think to have this functionality not deprecated and add a simple to use SaveEXR to memory option. In fact, it would be great to have even simpler functions that have an API that is the same as stbi_load and stb_write.

Expected behavior
Three things:

• Do not deprecate the simple-to-use interface
• Add Load/Save from/to memory
• Consider an even simpler interface that matches stb headers to make integration trivial.

[syoyo]

@xelatihy Rather than extending existing legacy LoadEXR/SaveEXR API, we can propose new simple API based on stb interface, for example:

exr_load_from_file
exr_load_from_memory,
exr_load_half_from_memory(e.g. Load fp16 image as fp16 data)
exr_write_to_memory,
exr_is_half(check if images in .exr have all fp16)
...

And example code is something like:

int w, h, c;
if (exr_is_half(exrfile)) {
  uint16_t *img = exr_load_half_from_file(exrfile, &w, &h, &c);
} else {
  float *img = exr_load_from_file(exrfile, &w, &h, &c);
}

[xelatihy]

This proposal is actually might nicer! And we could deprecate the old ones.

I would love to have both the _from_file and _from_memory options.

[xelatihy]

Would be also great to have the stb requested number of channels on load that is very helpful when putting together apps quickly.

[syoyo]

You can propose API based on my draft idea and send PR. Contribution is always welcome.

[xelatihy]

Ok, I'll try to prepare a PR.

[xelatihy]

I took a look and it is that as simple. The easiest thing to do is to wrap into a coherent API what you have already implemented. But that would have some limitations in the API itself. I guess it may be better than nothing, but still not as nice as one would like.

I might take another look later as I get more time.

[syoyo]

LoadEXRFromMemory already exists.

Now I've added SaveEXRToMemory 0647fb3 So close the issue.