def extract_features(self): """Extracts features from the image""" """从图像中提取特征 """ if self.feature_type == 'sift': detector = cv2.xfeatures2d.SIFT_create() elif self.feature_type == 'surf': detector = cv2.xfeatures2d.SURF_create() elif self.feature_type == 'orb': detector = cv2.ORB_create(nfeatures=1500) else: logging.error("Admitted feature types are SIFT, SURF or ORB") sys.exit(0)

这是一个Python方法，它的作用是从图像中提取特征。具体解释如下：

- 方法名为extract_features，它属于一个类，通过self可以访问该类的属性和方法。
- 如果self对象的feature_type属性为'sift'，则创建一个SIFT特征检测器，赋值给detector变量。
- 如果self对象的feature_type属性为'surf'，则创建一个SURF特征检测器，赋值给detector变量。
- 如果self对象的feature_type属性为'orb'，则创建一个ORB特征检测器，其中nfeatures参数指定了最大特征点数为1500，赋值给detector变量。
- 如果self对象的feature_type属性既不是'sift'、'surf'、'orb'中的任何一种，则打印错误信息并退出程序。
- 最后返回detector变量，它是一个特征检测器对象，用于后续的特征提取。

相关问题

def extract_tuple(input_tuple, start_index, end_index): return input_tuple[start_index : end_index+1] In the terminal, run function call of extract_tuple with different arguments. For example, try extract_tuple((100,200,300,400,500,600), 1, 4) . What does it output?

When running the function call `extract_tuple((100, 200, 300, 400, 500, 600), 1, 4)`, the output will be:

(200, 300, 400, 500)

This is because the function `extract_tuple` takes three arguments: `input_tuple`, `start_index`, and `end_index`. It returns a new tuple that contains the elements of `input_tuple` starting from `start_index` up to `end_index` (inclusive).

In this case, `(100, 200, 300, 400, 500, 600)` is the `input_tuple`, `1` is the `start_index`, and `4` is the `end_index`. Therefore, it extracts the elements from index 1 to index 4 (inclusive), resulting in the tuple `(200, 300, 400, 500)`.

Token Token_stream::get()

The function `get()` in the `Token_stream` class reads and returns the next token from the input stream. It first checks if there is a token already in the buffer (i.e., `full` is true), and if so, it returns that token and sets `full` to false. If the buffer is empty, it reads the input stream and extracts the next token using the `cin >>` operator. It then checks if the token is a valid token (e.g., a number or a symbol). If it is not a valid token, the function throws a `runtime_error` with an appropriate error message. If the token is valid, it sets `full` to true and returns the token.