Edge detection based on background change

A method for detecting edges for an object in a scene, comprising:

• acquiring a static image of the scene when the scene is static;
• acquiring a live image of the scene including the object;
• constructing a reference image from the static image, and for each pixel in the live image:
• (a) testing if a gradient magnitude is greater than a first threshold and continuing to (b) if true, else labeling the pixel as not an object edge;
• (b) testing if the gradient magnitude is a local maximum and continuing to (c) if true, else labeling the pixel as not an object edge;
• (c) testing if a distance between the gradient magnitude at the pixel and a corresponding gradient magnitude of a corresponding pixel in the reference image is less than a second threshold and continuing to (d) if true, else labeling the pixel as an object edge;
• (d) testing if a distance between the gradient direction at the pixel and a corresponding gradient direction of a corresponding pixel in the reference image is less than a third threshold and continuing to (e) if true, else labeling the pixel as an object edge;
• (e) testing if a distance between an intensity at the pixel and a corresponding intensity of a neighboring pixel in a gradient direction of lower intensity is less than a fourth threshold and continuing to (f) if true, else labeling the pixel as an object edge;
• and
• (f) testing if a distance between the intensity at the pixel and a corresponding intensity of a neighboring pixel in a gradient direction of higher intensity is less than a fifth threshold and labeling the pixel as not a object edge if true, else labeling the pixel as an object edge.