It looks like memories have to be declared up front, and the memcpy instruction takes the memories to copy between as numeric literals. So I guess you can't us

It looks like memories have to be declared up front, and the memcpy instruction takes the memories to copy between as numeric literals. So I guess you can't use it to allocate dynamic buffers. But maybe you could decide memory 0 = heap and memory 1 = pixel data or something like that?