The authors in [15] studied on how to choose good samples
for Haar-like cascade classifiers and image post-processing
methods to achieve good location results. while the authors
in [16] introduced the classifier which was trained through
histogram of oriented gradients (HOG) features to judge the
likelihood of candidate plates detected by Haar-like classi-
fier, and selected the candidate with highest likelihood as
the final plate, in order to reduce the false positives. This
method was tested on 3000 images to obtain a recall rate of
95.2%, and accuracy of 94.0% as opposed to 66.4% without
using HOG features.