- when you threshold a Gradient magnitude, you get disconnected lines
- high threshold causes missing edges
- low threshold causes too much noise and false positives
- connect edges to create long edges
- define low and high thresholds
- < Low = not an edge
- > High = strong edge
- else = weak edge
- If gradient is between Low and High, loop through neighbors
- declare it edge if connected to a strong pixel directly or via other weak pixels
- from weak pixel, traverse until you find strong and connect, otherwise discard