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Two possible difficulties may occur in the above Hough transform method: (a) the shape has to
be described by an equation, and (b) the number of parameters (dimensions of the
parameter space) may be high. Given the two equations:
we still have to search the remaining dimensions of the parameter space. These two
difficulties can be avoided by the generalized Hough transform shown below.
Preparation: build a table for the given shape
Prepare a table with entries each indexed by an angle ( )
which increases from 0 to 180 degrees with increment , where is the
resolution of the gradient orientation (see below).
Define a reference point somewhere inside the 2D shape (e.g., the
gravitational center). For each point on the boundary of the shape, find two
parameters
and the gradient direction . Add the pair to the table entry with its
closest to .
Prepare a 2D Hough array initialized to 0.
1.
Generalized Hough transform http://fourier.eng.hmc.edu/e161/lectures/hough/node6.html
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