Calculates the gray-level histogram around a set of key points.
image: Input image. If a color image is received, its intensity will be used.
points: Points of interest in world coordinates. An N-by-2 or N-by-3 matrix.
radius: Radius of the region-of-interest (ROI) around each key point on which the histogram is calculated, in pixels.
shape: The shape of the ROI around each key point.
histogram: a histogram for each key point. An N-by-K integer matrix, where N is the number of key points and K is the length of the histogram, which depends on the maximum possible (not actual) value in the input image.