Rapid edge detecting method based on orthogonal polynomial fitting

Abstract

A rapid edge detecting method based on orthogonal polynomial fitting belongs to the field of subpixel image edge detecting. The two-dimensional edge detecting method utilizes a spatial moment to calculate the projection direction of an edge and convert two-dimensional edge detecting into one-dimensional edge detecting according to a projection formula during every window image numeralization processing, and avoids complex operation needed by gray curved surface fitting. An analytic formula for calculating a one-dimensional edge point position is obtained by applying the orthogonal polynomial fitting, and the difficult problem that a fitting method generally cannot obtain an analytical solution is solved effectively. The analytic formula is simple in form and contains relatively little inner product computation, and the edge point position and the edge normal direction which are obtained finally are utilized to confirm the position of an edge straight line in a window image. The method improves operating speed greatly, can be suitable for a two-dimensional detecting process which is high in requirement for instantaneity, and integrates the characteristics that a moment-based method or an interpolation method is high in operating speed and a fitting method is not sensitive to image noise. Therefore, the accuracy and the speed of the edge detecting are improved greatly.

Description

technical field [0001] The invention belongs to the field of sub-pixel image edge detection, in particular to a fast edge detection method based on orthogonal polynomial fitting. Background technique [0002] The most basic feature of an image is the edge. The so-called edge refers to the collection of pixels whose surrounding pixel gray levels have a step change or a roof change. The edge detection methods used in the early days are mostly pixel-level, and the positioning accuracy of these methods is an integer pixel. , that is, it can be judged that the edge position is in a certain pixel, but it cannot be further subdivided in this pixel. However, with the continuous improvement of the measurement accuracy requirements of industrial inspection, the pixel-level accuracy can no longer meet the actual detection requirements. The pixel method came into being. [0003] The existing sub-pixel-level edge detection methods can be summarized into three types: the method based on ...

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Problems solved by technology

[0008] In order to solve the existing sub-pixel edge detection methods, the methods based on moments or interpolation are relatively susceptible to interference from image noise, and the existing fitting methods do not have an analytical formula for calculating edge points, which leads to In the process of two-dimensional edge detection, fitting operation is required, especially in two-dimensional edge detection, surface fitting operation is required, which makes the operation process complicated, the solution speed is slow, and it cannot adapt to the two-dimensional edge with high real-time requirements. The technical problem of detection, the present invention provides a kind of fast edge detection method based on orthogonal polynomial fitting

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