Opencv的绘图

用 OpenCV 标注 bounding box 主要用到下面两个工具——cv2.rectangle() 和 cv2.putText()。用法如下：

# cv2.rectangle()
# 输入参数分别为图像、左上角坐标、右下角坐标、颜色数组、粗细
cv2.rectangle(img, (x,y), (x+w,y+h), (B,G,R), Thickness)

# cv2.putText()
# 输入参数为图像、文本、位置、字体、大小、颜色数组、粗细
cv2.putText(img, text, (x,y), Font, Size, (B,G,R), Thickness)

def plt_bboxes(img, classes, scores, bboxes, figsize=(10,10), linewidth=1.5):
    """Visualize bounding boxes. Largely inspired by SSD-MXNET!
    """
    #fig = plt.figure(figsize=figsize)
    #plt.imshow(img)
    height = img.shape[0]
    width = img.shape[1]
    colors = dict()
    for i in range(classes.shape[0]):
        cls_id = int(classes[i])
        if cls_id == 15:
            score = scores[i]
            if cls_id not in colors:
                colors[cls_id] = (random.random(), random.random(), random.random())
            ymin = int(bboxes[i, 0] * height)
            xmin = int(bboxes[i, 1] * width)
            ymax = int(bboxes[i, 2] * height)
            xmax = int(bboxes[i, 3] * width)
            #rect = plt.Rectangle((xmin, ymin), xmax - xmin,
                                 #ymax - ymin, fill=False,
                                 #edgecolor=colors[cls_id],
                                 #linewidth=linewidth)
            #plt.gca().add_patch(rect)
            class_name = str(cls_id)
            img=cv2.rectangle(img,(xmin,ymin),(xmax,ymax),(0,255,0),2)
            s = 'person/%.3f' % (score)
            img=cv2.putText(img,s,(xmax+2,ymin-2), cv2.FONT_HERSHEY_DUPLEX, 0.5, (0,255,0), 1)
            cv2.imwrite('new.jpg', img)
            cv2.namedWindow('Detection')
            cv2.imshow('Detection',img)
            cv2.destroyAllWindows()  
            if 
            cv2.waitKey(0)
            #plt.gca().text(xmin, ymin - 2,
                           #'{:s} | {:.3f}'.format(class_name, score),
                           #bbox=dict(facecolor=colors[cls_id], alpha=0.5),
                           #fontsize=12, color='white')
    #plt.show()