I literally had a dream about a web-based sketch image search a couple of days ago. I wondered whether or not I could write such a thing. Spoiler alert: I could. And here it is: skrch.dvt.name. I’ll make more posts about how it works and how I’ll make it better soon enough.
It basically uses histograms to analyze picture similarity. Right now, the histogram is three-dimensional (hue/saturation + y-coord) but for more accurate results I may have to make the histograms n-dimensional, where n >= 3. I’ve also been reading about SURF methods and template matching, but that may be overkill for comparing a simple sketch to a complex image (the sketch may be more representative than a template may like) so I’m not sure if that’s a good approach.