I dont know any way to do this, in VTDbManager I am using my own procedure to bitBlt in-memory RGBA data, but this is part of another procedure, so I can't write you a sorce code.
In the principe it is pixel-by-pixel routine, but with optimised access to memory :
  • - lock - do everything - unlock
    - use block memory moves (rows of 4 byte pixels)
    - precomputized values of offsets (dest.x-src.x)*4
    - and so on...