Scoping context up front and looping over channels first.
Scoping context up front and looping over channels first.

This didn't show much of any performance improvement, but it seemed worthwhile keeping in any case...

appleseedhq/gaffer,GafferHQ/gaffer,johnhaddon/gaffer,GafferHQ/gaffer,ivanimanishi/gaffer,johnhaddon/gaffer,johnhaddon/gaffer,GafferHQ/gaffer,chippey/gaffer,appleseedhq/gaffer,boberfly/gaffer,ImageEngine/gaffer,chippey/gaffer,lucienfostier/gaffer,lucienfostier/gaffer,andrewkaufman/gaffer,ImageEngine/gaffer,lucienfostier/gaffer,hradec/gaffer,andrewkaufman/gaffer,ivanimanishi/gaffer,appleseedhq/gaffer,ImageEngine/gaffer,GafferHQ/gaffer,hradec/gaffer,GafferHQ/gaffer,hradec/gaffer,hradec/gaffer,ivanimanishi/gaffer,lucienfostier/gaffer,andrewkaufman/gaffer,andrewkaufman/gaffer,boberfly/gaffer,andrewkaufman/gaffer,johnhaddon/gaffer,appleseedhq/gaffer,boberfly/gaffer,hradec/gaffer,chippey/gaffer,ivanimanishi/gaffer,chippey/gaffer,johnhaddon/gaffer,boberfly/gaffer,ImageEngine/gaffer