# Number of haar features

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## Number of haar features

 Hi, In the original Viola Jones paper on face detection, they say there are more than 180,000 haar features in a 24x24 subwindow. Anyone know how this is calculated?
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## Re: Number of haar features

 --- In [hidden email], "sabatier_sabrika" wrote: > > Hi, > > In the original Viola Jones paper on face detection, they say there are more than 180,000 haar features in a 24x24 subwindow. > > Anyone know how this is calculated? > Hi, According to my understanding, the calcaulating process is as follows: As for a 24*24 window, there are twenty-three types of subwindow.(2*2, 3*3, 4*4, 5*5, ..., 24*24). Let's pick up 4*4(A) for example. In the 24*24 subwindow, the number of A(4*4) is 21*21(441). Every A has four haar features. So we can get 441*4(1764) haar features for 4*4.   So, (22*22 + 21*21 + 20*20 +...+ 1*1)*4 + (23*23)*3 + (24*24)*1      3*3     4*4     5*5         24*24     2*2          1*1 The above is my understanding. However, I found that the result is less than 180,000. Can some one tell me what's wrong with my calculation?