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Features from accelerated segment test (FAST) is a corner detection method, which could be used to extract feature points and later used to track and map objects in many computer vision tasks. FAST corner detector was originally developed by Edward Rosten and Tom Drummond, and published in 2006. The most promising advantage of FAST corner detector is its computational efficiency. Referring to its name, it is fast and indeed it is faster than many other well-known feature extraction methods, such as difference of Gaussians (DoG) used by SIFT, SUSAN and Harris. Moreover when machine learning method is applied, a better performance could be achieved which takes less time and computational resources. FAST corner detector is very suitable for real-time video processing application because of high-speed performance. == Segment test detector == FAST corner detector uses a circle of 16 pixels (a Bresenham circle of radius 3) to classify whether a candidate point p is actually a corner. Each pixel in the circle is labeled from integer number 1 to 16 clockwise. If a set of N contiguous pixels in the circle are all brighter than the intensity of candidate pixel p (denoted by Ip) plus a threshold value t or all darker than the intensity of candidate pixel p minus threshold value t, then p is classified as corner. The conditions can be written as: *Condition 1: A set of N contiguous pixels S, ∀ x ∈ S, the intensity of x (Ix) > Ip + threshold t *Condition 2: A set of N contiguous pixels S, ∀ x ∈ S, Ix < Ip - t So when either of the two conditions is met, candidate p can be classified as a corner. There is a tradeoff of choosing N, the number of contiguous pixels and the threshold value t. On one hand the number of detected corner points should not be too many, on the other hand, the high performance should not be achieved by sacrificing computational efficiency. Without the improvement of machine learning, N is usually chosen as 12. A high-speed test method could be applied to exclude non-corner points. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Features from accelerated segment test」の詳細全文を読む スポンサード リンク
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