nms

fast rcnn的nms代码

code

# --------------------------------------------------------
# Fast R-CNN
# Copyright (c) 2015 Microsoft
# Licensed under The MIT License [see LICENSE for details]
# Written by Ross Girshick
# --------------------------------------------------------

import numpy as np
def nms(dets, thresh):
    """Pure Python NMS baseline."""
    x1 = dets[:, 0]
    y1 = dets[:, 1]
    x2 = dets[:, 2]
    y2 = dets[:, 3]
    scores = dets[:, 4]
    areas = (x2 - x1 + 1) * (y2 - y1 + 1)
    order = scores.argsort()[::-1]  # 从大到小排序
    keep = []
    while order.size > 0:
        i = order[0]
        keep.append(i)
	
	# 下面是求score最大的和其他框的相交区域面积
        xx1 = np.maximum(x1[i], x1[order[1:]])
        yy1 = np.maximum(y1[i], y1[order[1:]])
        xx2 = np.minimum(x2[i], x2[order[1:]])
        yy2 = np.minimum(y2[i], y2[order[1:]]）
        w = np.maximum(0.0, xx2 - xx1 + 1)
        h = np.maximum(0.0, yy2 - yy1 + 1)
        inter = w * h

        ovr = inter / (areas[i] + areas[order[1:]] - inter)  # 相交的部分/相并的部分

        inds = np.where(ovr <= thresh)[0]    # np.where返回一系列索引值(第几个位置)，取出索引值的【0】

        order = order[inds + 1]    # 来继续排除后面一个
    return keep

图片分析

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参考

• nms实现：https://zhuanlan.zhihu.com/p/64423753
• https://blog.csdn.net/leviopku/article/details/80886386
• numpy.where() 有两种用法：https://www.cnblogs.com/massquantity/p/8908859.html