[RFC] impr: Extend `texture.write()` capabilities

Current API

texture.write(image);
texture.write([layer0, layer1, layer2]);
texture.write(rawBytes, mipLevel);

Useful for whole-texture writes, but limited when it comes to capabilities.

Proposed API Shape

Exact Image Writes

texture.write(image);

Writes as-is. If the image size does not match the target write area, throw.

Explicit Resize

texture.write(image, { resize: true });

Resize is opt-in (since it involves running an entire resample pipeline).

Region Writes

texture.write({
  source: image,
  origin: [32, 16],
  size: [128, 128],
});

Writes into a destination rectangle.

Source Crop

texture.write({
  source: image,
  sourceOrigin: [8, 8],
  sourceSize: [64, 64],
  origin: [128, 32],
});

Crops source pixels before writing.

Blob Resize Path

await texture.writeAsync({
  source: blob,
  resize: true,
});

A resize path that does not involve running WebGPU pipelines but is asynchronous.

So conceptually:

const bitmap = await createImageBitmap(blob, { resizeWidth, resizeHeight });
texture.write({ source: bitmap, size, resize: false });

Single-Channel Writes

texture.write({
  channels: {
    r: roughnessMap,
    g: metalnessMap,
    b: aoMap,
    a: maskMap,
  },
});

Single-Channel With Region

texture.write({
  channels: {
    r: roughnessMap,
  },
  origin: [32, 16],
  size: [128, 128],
});

Start by locating the existing texture.write() implementation and any writeAsync entry point. Compare their current handling with the proposed exact, resize, region, crop, blob, and channel forms. Done means the agreed API behavior is implemented and each documented usage shape is covered by appropriate validation.