AVOIDANCE OF ADDITIONAL ALIASING IN MULTIPASS IMAGE ROTATIONS

The two-pass (or multipass) image geometric transformation algorithm i s ideally suited to real-time, parallel implementation, but is known t o introduce frequency aliasing during rotation, over and above any ali asing which may result from the usual one-pass algorithm. In this work , we develop a unified framework and theory that precisely explains th is added-aliasing for many of the well-known multipass algorithms, and show that it is usually less than might be expected at first sight. I n some cases, the aliasing occurs in nondestructive, and therefore, th eoretically recoverable, forms. We also show that the aliasing is very easily reduced, or avoided altogether, while commenting that this pro blem should be considered as a special case of a general alias-avoidan ce strategy in geometric transformation. Finally, we include some exam ples of multipass image rotations which seem to confirm our prediction s.