On Wednesday 29 November 2006 13:56, Matt Mahoney wrote: > How is a raster scan (16K vector) of an image useful? The difference > between two images of faces is the RMS of the differences of the images > obtained by subtracting pixels. Given an image of Tom, how do you compute > the set of all images that look like Tom? > > Humans perceive images by reducing them to a small set of complex features, > which can be compared in a space with much fewer dimensions.
Certainly. The n-space representation at that early stage is primarily an abstraction for thinking about the process mathematically. In humans, the retina starts with more like a 16M raster but reduces it precipitously before even sending it down the optic nerve. On the other hand, visual cortex has not one but many 2-d maps where various functions of images are manipulated in a very straightforward way -- the raster form is still used quite a bit before the higher abstractions are generated. One way of computing the set of images that look like Tom would be to follow from your one image along a trajectory that you knew maintained invariants in pose, orientation, lighting, etc, until you hit the hypersurface that was the images of Dick, and then shift the whole Dick region the opposite offset. I doubt it actually happens at this level in vision, but I bet the basic mechanism, at higher levels, is *extremely* common in carrying expectations from an experience to a new situation. --Josh ----- This list is sponsored by AGIRI: http://www.agiri.org/email To unsubscribe or change your options, please go to: http://v2.listbox.com/member/?list_id=303
