Color adapter (§17 "color") over the RGBA 4-tuple (plan P4-2).
Component-wise linear interpolation of straight (non-premultiplied) RGBA with
no clamping (§60a extended range) and no color-space conversion: the
tuple carries no space, so mixing happens in whatever space the author wrote,
and §60a's transfer functions stay a rendering concern.
Alpha is interpolated like any other component. Each component is read before
it is written, so this adapter tolerates out aliasing either endpoint.
Color adapter (§17 "color") over the RGBA 4-tuple (plan P4-2).
Component-wise linear interpolation of straight (non-premultiplied) RGBA with no clamping (§60a extended range) and no color-space conversion: the tuple carries no space, so mixing happens in whatever space the author wrote, and §60a's transfer functions stay a rendering concern.
Alpha is interpolated like any other component. Each component is read before it is written, so this adapter tolerates
outaliasing either endpoint.