Rendering to a single Bitmap object from multiple threads

Question

What im doing is rendering a number of bitmaps to a single bitmap. There could be hundreds of images and the bitmap being rendered to could be over 1000x1000 pixels.

Answer 1

One approach would be to render all the small bitmaps onto an ersatz bitmap, which would just be a two-dimensional int array (which is kind of all a Bitmap really is anyway). Once all the small bitmaps are combined in the big array, you do a one-time copy from the big array into a real Bitmap of the same dimensions.

I use this approach (not including the multi-threaded aspect) all the time for complex graphics on Windows Mobile devices, since the memory available for creating "real" GDI+ Bitmaps is severely limited.

You could also just use a Bitmap as you originally intended. Bitmap is not guaranteed to be thread-safe, but I'm not sure that would be a problem as long as you could assure that no two threads are ever overwriting the same portion of the bitmap. I'd give it a try, at least.

Update: I just re-read your question, and I realized that you're probably not going to see much (if any) improvement in the overall speed of these operations by making them multi-threaded. It's the classic nine-women-can't-make-a-baby-in-one-month problem.