[image processing]SIFT AND SURF descriptors

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http://www.cs.utexas.edu/~grauman/courses/fall2009/slides/lecture16_bow.pdf

• SIFT descriptor:
• Use histograms to bin pixels within sub-patches according to their orientation.
  
  • 4*4=16 subpatches, for each one have histogram with 8 bin, summing up get a vector in 128 dimensions
• Making the descriptor rotation invariant by
  
  • Rotate patch according to its dominant gradient orientation and puts the patches into a canonical orientation
• ad: Extraordinarily robust matching technique -> can handle change in viewpoints(60) and significant changdes in illumination(day and night)