Test invalid input for seed
Test invalid input for selem
Add full test coverage for corner_subpix and fix bug
Test union of differing geometric transforms
Test 90deg rotation for similarity transform
Fix docstring of skimage.filter.rank.threshold_percentile
Test invalid input for unwrap_phase
Comment special case when local patch around is constant
Improve description of subpixel corner localization
Merge pull request #1008 from ahojnnes/coverage

Improve coverage and docstrings for subpixel corner detection