Support use of resize() function in Web Workers

[852Kerfunkle]

Is your feature request related to a problem? Please describe.
It would be nice to have an alternative for resizing images in a webworker, if that is somehow possible (that's half the problem I'm trying to solve with glTF-Transform).

Describe the solution you'd like
Looking at ndarray-pixels (browser-get-pixels.ts), since it uses Image (not available in web workers) as well as document.createElement('canvas') (can probably be worked around with new OffscreenCanvas()), that might be tricky.

I'd be happy to contribute something (to ndarray-pixels?), if you let me know what the requirements are (regarding dependencies, etc).

[852Kerfunkle]

So, there's ImageBitmap and createImageBitmap now.

This works (in chromium at least):

    for (const t of document.getRoot().listTextures()) {
        const image = t.getImage();
        
        if (image) {
            const res = await createImageBitmap(new Blob([image]), {resizeWidth: width, resizeHeight: height});

            const canvas: any = new OffscreenCanvas(width, height);
            const context = canvas.getContext('2d');
            context.drawImage(res, 0, 0);

            const blob: Blob = await canvas.convertToBlob({type: t.getMimeType()});

            t.setImage(new Uint8Array(await blob.arrayBuffer()));
        }
    }

But probably isn't very widely supported.

[donmccurdy]

I'd be glad to take a PR on ndarray-pixels for this (or something similar) if you're willing to try that! Otherwise TBD, I've been hoping squoosh/lib would get Web support eventually and would solve some of these issues, but unclear when/if that will happen.

[852Kerfunkle]

Sure, gladly would contribute. Would you be alright with throwing exceptions if browser support for required functions (createImageBitmap, OffscreenCanvas, offscreen canvas 2d support, convertToBlob) is missing - for the inside web worker case, that is?

[donmccurdy]

Sorry for the delayed reply here! I'd be fine with exceptions being thrown. I'd probably just let the browser hit these errors rather than explicitly checking for support.

• /cc Alternative textureResize() implementations #647

[donmccurdy]

After #775 we now have two implementations of texture resizing within this project, one that is cross-platform with ndarray-pixels, and another that is much faster but Node.js-only, based on Sharp. I think I've done as much as I am willing to do within this codebase to make this feature cross-platform, but unfortunately none of these implementations support Web Workers today.

I'd still be glad to discuss this on the ndarray-pixels repository, if someone wants to make a PR there. Another option would be too look into replacing sharp (used by textureCompress now) with wasm-vips. That might get us the best of all worlds — good performance and cross-platform support, but I don't know yet whether wasm-vips runs in a Web Worker either.