subsampling has bugs. checked in func_test.cpp exposes them
subsampling has bugs. checked in func_test.cpp exposes them

git-svn-id: c578352ef3581197c7d0052ca74e10c73f7d7a72@221 f3e031b0-0bc6-11df-b730-f17d7b42d8b9

mit-gfx/ImageStack,mit-gfx/ImageStack,mit-gfx/ImageStack,mit-gfx/ImageStack