I've always liked to draw, and always been fairly good at it. For a while I wondered if I might be a drawing savant, but decided my drawing skill had changed and developed too much for that. For me to be a savant, I would have to have started drawing with much more detail and grasp of perspective than I did.
Even if I wasn't a savant, I still wonder if my autism hasn't played a role in shaping my drawing ability and making me like to draw. I don't draw the same kinds of things most autistic artists do --- I think of autistic artists as all choosing to draw the sort of sprawling, imposing cityscapes that Stephen Wiltshire draws, while I draw mostly human figures*, with occasional natural landscapes. I do tend to draw insanely detailed line drawings, with very dark and heavy lines, though. Also, I've always drawn pictures piecewise --- do small parts one by one, in great detail, and see if they fit together --- which sometimes gives me trouble with proportions. But I have even more trouble when I try to sketch out a general plan for a picture; when I do that, things quickly get too large. It seems the only way I can stay on the paper is to keep the part I'm working on very small. This difficulty maintaining scale looks a bit like the fragmentation observed by Fein, Lucci and Waterhouse in their 1990 study comparing 34 autistic children to 32 normal children in their ability to reproduce drawings of geometric figures they were given and their ability to draw a child freehand. (If you can access the full article, it includes some sample drawings.) I also can draw about equally well from memory, from direct observation and from photographs, although my ability to draw something from memory depends on my understanding of what I see. I don't have a perfect photographic memory, so conceptual understanding of the structure of whatever I'm trying to draw is needed to fill the gaps in my memory of it. That can go the other way, too; as I draw something, I usually come to understand it better.
That's probably the biggest difference between my drawing and a savant's drawing: for me, drawing is a long, intense, highly intellectual process, while they just seem to bang them out automatically.
*I was interested to see this article, which apparently unearths an autistic drawing savant who prefers to draw human figures, and also who doesn't draw from memory. She is also female, which led me to wonder if this might be another sex difference within autism --- just as autistic girls tend to be more interested in pretending and fiction writing and art than autistic boys, maybe female autistic artists tend to choose different subject matter for their pictures. Most of the famous drawing savants are boys and men, after all...