The current drawImage pipelines that deal with image scaling can call
different algorithms depending on whether the current clip totally
encompasses the operation, or if it is rectangular and clips part
of the operation, or if it is non-rectangular.

The different algorithms used in these different cases do not always
agree pixel for pixel with each other. In some cases, the different
choices can result in filtering being applied or ignored which causes
a major change in the resulting output.

All results from drawImage should be identical under all types of
clipping.