2013-06-12 08:16:28 -0600 | received badge | ● Student (source) |
2013-05-17 04:05:44 -0600 | asked a question | SIFT Detection Octave Calculation I'm not quite sure if i got the calculation of SIFT keypoint Detection. I looked into the nonfree/sift.cpp file in the SIFT::operator() and adjustLocalExtrema Method. There are some bitmask operations which allow to transport the fractional part of the octave to the SIFT Descriptor. Nevertheless i do not quite understand the data representation. In SIFT::operator() a local variable named firstOctave is initialized with -1 (line 731, nonfree/sift.cpp, branch 2.4). Then there are 2 possibilities: If useProvidedKeypoints == true, the following code is executed: firstOctave is first overwritten zero and then by a min-Expression. Whatever octave will be, the value stays 0 (i run a test on this and octave never was <0). The second posibility is when useProvidedKeypoints == false: This is the main issue. If useProvidedKeypoints == false the first code example will never be executet. So, firstOctave will be -1 everytime this second code will be executed. My Questions are:
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