# Catalogue of Artificial Intelligence Techniques

## Hough Technique

**Keywords:**
array, parameter
space

### Categories: Pattern Recognition and Image Processing

Author(s): **H.W. Hughes**

The Hough technique is a method of detecting parametric image features, such as curves. A point on a curve undergoes a transform to form a path in parameter space that represents all possible curves that could pass through that point. The parameter space is represented by an array whose elements are incremented each time a path passes across them. By repeating the transform for each point, local peaks are formed in parameter space representing points lying on the same curve in image space. The height of the peak indicates the number of points on the curve. To detect straight lines, for a point at position $(x,y)$ the transform $r=xcos\theta +ysin\theta $ is usually used to produce a sinusoidal curve in$(r,\theta )$

parameter space. This technique can be used on any curve that can be parameterised, though the amount of computation required increases rapidly with the number of parameters.

### References:

- Ballard, D.H. and Brown, C.M.,
*Computer Vision*, Prentice Hall, Englewood Cliffs, N.J., 1982, pp.123--131.

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