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A color picture of an engine The Sobel operator applied to that image. The Sobel operator, sometimes called the Sobel–Feldman operator or Sobel filter, is used in image processing and computer vision, particularly within edge detection algorithms where it creates an image emphasising edges.
As a pre-processing step to edge detection, a smoothing stage, typically Gaussian smoothing, is almost always applied (see also noise reduction). The edge detection methods that have been published mainly differ in the types of smoothing filters that are applied and the way the measures of edge strength are computed.
The Canny edge detector is an edge detection operator that uses a multi-stage algorithm to detect a wide range of edges in images. It was developed by John F. Canny in 1986. Canny also produced a computational theory of edge detection explaining why the technique works.
In image processing, a Robinson compass mask is a type of compass mask used for edge detection. It has eight major compass orientations, [ 1 ] each will extract the edges in respect to its direction. A combined use of compass masks of different directions could detect the edges from different angles.
Edge detection using Sobel filter of hyperbolic components of Mandelbrot set. Because the Mandelbrot set is full, [12] any point enclosed by a closed shape whose borders lie entirely within the Mandelbrot set must itself be in the Mandelbrot set.
Uses edge detection techniques, such as the Canny edge detection, to find edges. Changes in lighting and color usually don't have much effect on image edges; Strategy: Detect edges in template and image; Compare edges images to find the template; Must consider range of possible template positions; Measurements:
The pixels with the largest gradient values in the direction of the gradient become edge pixels, and edges may be traced in the direction perpendicular to the gradient direction. One example of an edge detection algorithm that uses gradients is the Canny edge detector. Image gradients can also be used for robust feature and texture matching.
The Hessian affine region detector is a feature detector used in the fields of computer vision and image analysis. Like other feature detectors, the Hessian affine detector is typically used as a preprocessing step to algorithms that rely on identifiable, characteristic interest points .