Region is a contiguous set. The edge direction is perpendicular to the gradient direction which points in the direction of image function growth. The direction of the crack edge is that of increasing brightness, and is a multiple of 90 degrees, while its magnitude is the absolute difference between the brightness of the relevant pair of pixels. Topological properties of images are invariant to rubber sheet transformations . Stretching does not change contiguity of the object parts and does not change the number of holes in regions.
Convex hull is used to describe topological properties of objects.
The convex hull is the smallest region which contains the object, such that any two points of the region can be connected by a straight line, all points of which belong to the region. 2.10 Histograms Brightness histogram provides the frequency of the brightness value z in the image. Open the Histogram project Running the project displays histograms of the original image and the equalized image. Open the Histogram workspace Display histograms of the original image and the equalized image using the histogram display capabilities of cantata.