Converting photorealistic rasters to vector format

People, I see no appropriate tools for this task. I've tested some of vectorization tools, but without hi-grade support of gradient fills they cannot produce an output, deserving more than "exit without saving". Moreover, this thing (hi-grade gradient fills support) is absent elsewhere too. I mean file formats specification. Mesh-based gradient fills could be compared with drawing curves with the aid of only polylines, without splines nor Bezier curves. As a result there is alternative- or ugly looking image, reminding cheap Japanese cartoon, or huge file, surpassing source bitmap in sizes. If you have an interest, what really could be done to solve this problem, visit www.smartfills.com. Even if you have no intention to play with soft, availible there, look at the gallery. There are some vector images, converted to raster. At least you'll get to know, which vector graphic could have been (and surely will be).