Shape context

shape context 是一种描述，参见
A performance evaluation of local descriptors



Shape context is similar to the SIFT descriptor, but is based on edges. Shape context is a 3D
histogram of edge point locations and orientations. Edges are extracted by the Canny [5] detector.
Location is quantized into 9 bins of a log-polar coordinate system as displayed in gure 1(e)
with the radius set to 6, 11 and 15 and orientation quantized into 4 bins (horizontal, vertical and
two diagonals). We therefore obtain a 36 dimensional descriptor.