python - int()参数必须是字符串，类似字节的对象或数字，而不是 'NoneType'

Question

我尝试开发对象检测API，在实现过程中发生错误，

import cv2
cap = cv2.VideoCapture(0)

with detection_graph.as_default():
 with tf.Session(graph=detection_graph) as sess:
   while(True):
     ret,image_np =cap.read()
     image_np_expanded = np.expand_dims(image_np,axis=0)
     image_tensor =detection_graph.get_tensor_by_name('image_tensor:0')
     boxes = detection_graph.get_tensor_by_name('detection_boxes:0')
     scores = detection_graph.get_tensor_by_name('detection_scores:0')
     classes = detection_graph.get_tensor_by_name('detection_classes:0')
     num_detections = detection_graph.get_tensor_by_name('num_detections:0')

     (boxes,scores,classes,num_detections) = sess.run(
             [boxes,scores,classes,num_detections],
             feed_dict={ image_tensor:image_np_expanded})
     vis_util.visualize_boxes_and_labels_on_image_array(
             image_np,
             np.squeeze(boxes),
             np.squeeze(classes).astype(np.int32),
             np.squeeze(scores),
             category_index,
             use_normalized_coordinates=True,
             line_thickness=8)

     cv2.imshow('image',cv2.resize(image_np,(1280,960)))
     if cv2.waitkey(25) & 0xFF == ord('q'):
         break
         cv2.destroyAllWindows()
         cap.release()

Answer 1

您是否检查流是否正确打开。您可以使用下面的行来尝试。

cap.isOpened()

如果上述方法返回true，则表示读取文件没有问题。然后，您需要在下面的行中设置要读取的帧。

cap.set(cv2.CAP_PROP_POS_MSEC，frameNumber)

您可以在直播时将frameNumber设置为1000(以millisec为单位)!