Saturday, November 28, 2015

Reading 33 : Using shape context for sketch recognition

Citation:
Belongie, Serge, Jitendra Malik, and Jan Puzicha. "Shape matching and object recognition using shape contexts." Pattern Analysis and Machine Intelligence, IEEE Transactions on 24.4 (2002): 509-522.
Publication Link

Summary:
This paper is very similar to the $p algorithm, in the fact that it tries to match every point in the candidate to some point in the template. We take the set of vectors originating from a point to all other sample points on a shape. These vectors express the configuration of the entire shape relative to the reference point.

Discussion:
The following library has Javascript implementations of Haudroff Distance and Shape Context. This was the motivation behind looking unto Shape Context as an alternative means of template matching.

https://github.com/kjkjava/Sketchy.js/tree/master

 The shape descriptor of a point is represented as a relative distribution over positions, in histogram bins of log-polar space. The cost of this matching for a point is defined using the chi-square statistic:
 

We choose the matching that minimizes the total cost of this matching.



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