In an image, an edge is a curve that follows a path of rapid change in image intensity. Edges are often associated with the boundaries of objects in a scene. Different algorithms are suited for detecting edges of straight lines, round objects, or arbitrarily shaped regions. Conversely, you can detect homogenous blocks that lack edges.
Edge detection is a technique for finding the boundaries of objects within an image.
You can display the boundaries of a single object or of all objects in an image.
The Hough transform detects lines in an image, including lines tilted at arbitrary angles from vertical and horizontal. The Hough transform tends to be quick, but can exhibit artifacts.
This example shows how to detect lines and identify the strongest lines in an image using the Radon transform.
Quadtree decomposition is useful as a first step in adaptive image compression. The decomposition involves subdividing an image into homogenous blocks.