Supporting range and segment-based hysteresis thresholding in edge detection

One of the important steps in gradient-based edge detection is thresholding, e.g., hysteresis thresholding in the Canny detector. Traditional approaches only use gradient magnitude as the criterion to select edge pixels. We introduce a novel saliency measure called supporting range. It measures the range along the gradient direction of an edge pixel in which its gradient magnitude is a local maximum. As the result, our approach can detect the edge pixels on object boundaries even if they have very low gradient magnitude. In addition, unlike the Canny detector, the proposed hysteresis thresholding approach is based on segments instead of individual pixels. This also makes the approach more robust to detect edge pixels on weak boundaries.