Windows rendering issue

[slimbuck]

The same PLY sometimes looks different (incorrect) on windows Chrome compared to macos Chrome:

This issue was reported by Henry Pearce.

[simonbethke]

@slimbuck when looking at the getContext() methods, there is no color-space defined. I would suggest to add the color-space as suggested by the LLM.

[slimbuck]

It turns out that mac hardware actually accumulates/blends to a 16bit tiled memory buffer before writing to the 8-bit target.

The discoloration only appears on the NVIDIA hardware because the GPU is actually accumulating/blending to RGBA8, resulting in rounding off over multiple layers.

The discoloration seems to be made worse by our use of premultiplied alpha blending, but I currently don't really understand why (see #421). Presumably blending hardware on NVIDIA is low-precision.