What's inside a haar cascade classifier in Open CV computer vision?
I need to translate an .xml OpenCV haar cascade to a txt file.
(Open CV has a Haar Feature-based Cascade Classifier for Object Detection.)
So I need to understand the xml. I'm wondering what are the "stages" and the "trees". Does a tree stand for a weak classifier? Are the trees in the same stage combined to be a strong classifier?? Are the stages cascaded???
In a tree from haarcascade_frontalface_alt.xml, it says:
<!-- tree 0 -->
<_>
<!-- root node -->
<feature>
<rects>
<_>3 7 14 4 -1.</_>
<_>3 9 14 2 2.</_></rects>
<tilted>0</tilted></feature>
<threshold>4.0141958743333817e-003</threshold>
<left_val>0.0337941开发者_JAVA百科907346249</left_val>
<right_val>0.8378106951713562</right_val></_></_>
<_>
I want to know what the numbers stand for.
I'll try explain the cascade xml meaning.
<_>
<!-- root node -->
<feature>
<rects>
<_>3 7 14 4 -1.</_>
<_>3 9 14 2 2.</_></rects>
<tilted>0</tilted></feature>
<threshold>4.0141958743333817e-003</threshold>
<left_val>0.0337941907346249</left_val>
<right_val>0.8378106951713562</right_val></_></_>
<_>
In
<_>3 7 14 4 -1.</_>
3,7 are the cordinate of the rectangle you'd like to sum using the square sum matrix (the integral image) 14 4 are the length and hieght of the rectangle -1 is the wieght of the rectangle (this is NOT the weight according to viola-johnes original article)
please denote that the rects are should be normalize to your detector size
if the rects sum passes the threashold value , then the right_val is sumed for the future, otherwise the left_sum is sumed
Good luck
S
Eureka! Page 370 of the OpenCV Reference Manual v2.1.
link http://picoforge.int-evry.fr/projects/svn/gpucv/opencv_doc/2.1/opencv.pdf
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