The texture data
OptionalpremultipliedWhether the pixel data is already premultiplied (e.g. produced by
createImageBitmap with premultiplyAlpha: 'premultiply').
This flag is only meaningful for ImageBitmap data sources. When true,
UNPACK_PREMULTIPLY_ALPHA_WEBGL is set to false at upload time to
prevent double-premultiplication. When false, the flag is set to true
so the WebGL driver premultiplies during the CPU→GPU copy (same path as
HTMLImageElement). When undefined, behaviour falls back to the legacy
assumption that all ImageBitmap sources are already premultiplied.
Platforms that call createImageBitmap without the
premultiplyAlpha: 'premultiply' option (e.g. WebPlatformChrome50)
must set this to false, otherwise the renderer composites straight-alpha
pixels against a blendFunc(ONE, ONE_MINUS_SRC_ALPHA) equation and
produces incorrect results on older WPEWebKit.
OptionalpremultiplyPremultiply alpha when uploading texture data to the GPU
TextureData that is used to populate a CoreContextTexture