Currently, the Images spec strictly defines the color of each pixel in a gradient - the gradient-line is colored according to the defined interpolation between color stops, and then the image is painted according to what point on the gradient line a given pixel is closest to.

However, WebKit apparently dithers its gradients to produce a smoother overall appearance. I think this should be allowed! Random dithering is a great rendering strategy for making gradients look even smoother, especially when the endpoints are fairly close in color-space; it avoids the hard line where the color shifts up or down one channel-unit, which can be pretty visible in some circumstances.

So I propose that we add some normative text to allow dithering as a rendering strategy. I don't think we need to put in any strict requirements on how far from ideal the dithering is allowed to be; we can leave that up to QoI and just rely on reasonable fuzzy-matching for reftests.