NMS

NMS
非极大值抑制

def NMS(dects, threshold):
    
    # dects:[x1,y1,x2,y2,score]

    x1 = dects[:,0]
    y1 = dects[:,1]
    x2 = dects[:,2]
    y2 = dects[:,3]
    score = dects[:,4]

    nboxs = dects.shape[0]
    area = (x2-x1+1)*(y2-y1+1)
    order = score.argsort()[::-1] #score从大到小排列的indexs,一维数组

    result = []

    suppressed = np.array([0]*nboxs)

    for _i range(nboxs):
        i = order[_i]
        if suppressed[i] == 1:
            continue
        result.append(i)

        for _j in range(_i+1, nboxs):
            j = order[_j]
            if supressed[j] == 1:
                continue
            xx1 = np.max(x1[i], x1[j])
            yy1 = np.max(y1[i], y1[j])
            xx2 = np.min(x2[i], x2[j])
            yy2 = np.min(y2[i], y2[j])
            w = np.max(0, xx2-xx1+1)
            h = np.max(0, yy2-yy1+1)
            interface = w*h
            overlap = interface / (area[i]+area[j])

            if overlap >= threshold:
                supressed[j] = 1

    return result