AlphaType

How the alpha channel of a pixel buffer relates to its color channels. Carried on ImageInfo and consumed by MakeImage, readPixels, etc.

All values

Value	Storage
`Premul`	RGB is already multiplied by alpha. `(0.5, 0, 0, 0.5)` means 50% red at 50% alpha. Skia's preferred internal format.
`Unpremul`	RGB independent of alpha. `(1, 0, 0, 0.5)` means full red at 50% alpha. What CSS / SVG / browser color-pickers use.
`Opaque`	Alpha is implicitly 1. Saves a channel; the alpha bytes (if present) are ignored.