Added heuristic to allocate buffer for FAST features depending on input image resolution #27657
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vpisarev
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Aug 12, 2025
modules/features2d/src/fast.cpp
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| @@ -429,8 +429,10 @@ void FAST(InputArray _img, std::vector<KeyPoint>& keypoints, int threshold, bool | |||
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| CV_INSTRUMENT_REGION(); | |||
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| const size_t max_fast_features = _img.total() / 4; // Simple heuristic that depends on resoption. most propably the same may be safly reduced more | |||
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there are a few typos: 1) resoption => resolution, 2) propably => probably.
recommended comment: "Use a simple heuristic depending on the image resolution; can probably be reduced even further".
also, sizeof(KeyPoint) is 28 bytes. If, say, image has a modest (by modern standards) resolution of 24Mpix, the buffer will have size 168Mb, which is rather big and allocation of such a buffer may slowdown the function. I suggest to reduce max_fast_features to std::max(_img.total()/100, (size_t)1000); that will give at max 10K features for 1000x1000 image and 240K features for 24Mpix image — more than enough for any kind of registration/scene recognition/loop closure algorithm.
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…ut image resolution.
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vpisarev
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Aug 12, 2025
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Patch to opencv_extra has the same branch name.