Evaluation

Evaluation of a KcsXformSeq instance is done with either the optimized or non-optimized technique.

Optimized evaluation uses the composed transformation it constructed when told to optimize. It keeps a pointer to that optimized transformation in its private section. When asked to evaluate, it passes the information down to the optimized transformation.

Unoptimized evaluation is used when the sequence is not optimized. This implementation evaluates the data through the list of transformations sequentially. Between transformations, a buffer is used to hold the temporary calculations. The first step evaluates from the source buffer, while the last step evaluates into the destination buffer.

Up to two different extra buffers are used between non-endpoint transformations, depending on the layout of the data. They are swapped between eval()()s. If the composition of the transformations is different (for example, chunky and planar), two buffers are needed. If the implementation did not use this technique, the data from one complete pixel (or component set) overrides a different (set of) pixel. The eval()() method always alternates between two buffer pointers. Both buffer pointers point to the same buffer if an output buffer for a transformation is compatible with the input buffor for the next transformation. This can be optimized further if all buffer layouts describe a buffer that is compatible with the destination buffer supplied by the caller. In this case, the buffer pointers point to the destination buffer described. And if the caller is using the same buffer for source and destination, everything ultimately uses one buffer. Such buffers are KcsMemoryBlocks that can be resized.