1. nms

  1. def py_cpu_nms(dets, thresh):
  2.     x1 = dets[:,0]
  3.     y1 = dets[:,1]
  4.     x2 = dets[:,2]
  5.     y2 = dets[:,3]
  6.     areas = (y2-y1+1) * (x2-x1+1)
  7.     scores = dets[:,4]
  8.     keep = []
  9.     index = scores.argsort()[::-1]
  10.     while index.size >0:
  11.         i = index[0]       # every time the first is the biggst, and add it directly
  12.         keep.append(i)
  14.         x11 = np.maximum(x1[i], x1[index[1:]])    # calculate the points of overlap 
  15.         y11 = np.maximum(y1[i], y1[index[1:]])
  16.         x22 = np.minimum(x2[i], x2[index[1:]])
  17.         y22 = np.minimum(y2[i], y2[index[1:]])
  19.         w = np.maximum(0, x22-x11+1)    # the weights of overlap
  20.         h = np.maximum(0, y22-y11+1)    # the height of overlap
  22.         overlaps = w*h
  23.         ious = overlaps / (areas[i]+areas[index[1:]] - overlaps)
  25.         idx = np.where(ious<=thresh)[0]
  26.         index = index[idx+1]   # because index start from 1
  28.     return keep

2. xxxx

3. xxxx

4. xxxx

References

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