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2020-10-04 16:24:14 -0600	received badge	● Notable Question (source)
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2018-05-31 09:57:50 -0600	marked best answer	Why does knnMatch return a list of tuples instead of a list of DMatch? This stitching example https://docs.opencv.org/3.0-beta/doc/... pipes the output of `flann.knnMatch` to `cv2.drawMatchesKnn`. Since the reference pages do not come close to properly documenting the output of `knnMatch`: https://docs.opencv.org/3.1.0/dc/de2/... https://docs.opencv.org/3.1.0/d4/de0/... I decided to look at the implementation of `drawMatchesKnn`, but found something strange. In the python-code, the output of `knnMatch` is a list of lists of two `DMatch` objects: `matches[:3] == ( [[<DMatch 0x7ff57f981710>, <DMatch 0x7ff57f981130>], [<DMatch 0x7ff57f981330>, <DMatch 0x7ff57f981290>], [<DMatch 0x7ff57f981310>, <DMatch 0x7ff57f9816f0>]] )` However `drawMatchesKnn`, to which matches is passed, these two line suggest it is a list of `DMatch`es, instead of a list of lists of `DMatch`es, since there is only one index `[m]` not two `[m][n]`, https://github.com/opencv/opencv/blob... Moreover, this loop `for i,(m,n) in enumerate(matches):` in the first link also seems to ignore the second `DMatch` `n` in each sublist. What is this second `DMatch` in each item of matches? Why is `matches` a list of tuples of `DMatch`es, and not a list of 'DMatch`es? It seems as if I can ignore the second `DMatch`, yet I don't feel comfortable blindly doing so.
2018-05-31 09:57:50 -0600	received badge	● Scholar (source)
2018-05-31 09:57:46 -0600	commented answer	Why does knnMatch return a list of tuples instead of a list of DMatch? In the first link of the OP, they test whether the best test is at least 1.0/0.7 times better than the second best, and
2018-05-31 09:11:17 -0600	asked a question	Why does knnMatch return a list of tuples instead of a list of DMatch? Why does knnMatch return a list of tuples instead of a list of DMatch? This stitching example https://docs.opencv.org/3