EnsureProcessor() was returning early whenever a processor existed and
processor_dirty_ was false, without checking whether the file or direction
input had changed. As a result, switching Forward/Inverse in the main GUI
re-used the old processor and produced no visible difference.
Now EnsureProcessor() also compares the current inputs against the values
used to create last_processor_, so direction/file changes always trigger a
regeneration before the color transform job is emitted.
Mike-Solar
f131abc5f7