cv_bridge

cv_bridge contains a single class CvBridge that converts ROS Image messages to OpenCV images.

class cv_bridge.CvBridge

The CvBridge is an object that converts between OpenCV Images and ROS Image messages.

>>> import cv2
>>> import numpy as np
>>> from cv_bridge import CvBridge
>>> br = CvBridge()
>>> dtype, n_channels = br.encoding_as_cvtype2('8UC3')
>>> im = np.ndarray(shape=(480, 640, n_channels), dtype=dtype)
>>> msg = br.cv2_to_imgmsg(im)  # Convert the image to a message
>>> im2 = br.imgmsg_to_cv2(msg) # Convert the message to a new image
>>> cmprsmsg = br.cv2_to_compressed_imgmsg(im)  # Convert the image to a compress message
>>> im22 = br.compressed_imgmsg_to_cv2(msg) # Convert the compress message to a new image
>>> cv2.imwrite("this_was_a_message_briefly.png", im2)
compressed_imgmsg_to_cv2(cmprs_img_msg, desired_encoding='passthrough')

Convert a sensor_msgs::CompressedImage message to an OpenCV cv::Mat.

Parameters:
  • cmprs_img_msg – A sensor_msgs::CompressedImage message
  • desired_encoding –

    The encoding of the image data, one of the following strings:

    • "passthrough"
    • one of the standard strings in sensor_msgs/image_encodings.h
Return type:

cv::Mat
Raises:

CvBridgeError – when conversion is not possible.

If desired_encoding is "passthrough", then the returned image has the same format as img_msg. Otherwise desired_encoding must be one of the standard image encodings

This function returns an OpenCV cv::Mat message on success, or raises cv_bridge.CvBridgeError on failure.

If the image only has one channel, the shape has size 2 (width and height)

cv2_to_compressed_imgmsg(cvim, dst_format='jpg')

Convert an OpenCV cv::Mat type to a ROS sensor_msgs::CompressedImage message.

Parameters:
Return type:

A sensor_msgs.msg.CompressedImage message
Raises:

CvBridgeError – when the cvim has a type that is incompatible with format

This function returns a sensor_msgs::Image message on success, or raises cv_bridge.CvBridgeError on failure.

cv2_to_imgmsg(cvim, encoding='passthrough')

Convert an OpenCV cv::Mat type to a ROS sensor_msgs::Image message.

Parameters:
  • cvim – An OpenCV cv::Mat
  • encoding –

    The encoding of the image data, one of the following strings:

    • "passthrough"
    • one of the standard strings in sensor_msgs/image_encodings.h
Return type:

A sensor_msgs.msg.Image message
Raises:

CvBridgeError – when the cvim has a type that is incompatible with encoding

If encoding is "passthrough", then the message has the same encoding as the image’s OpenCV type. Otherwise desired_encoding must be one of the standard image encodings

This function returns a sensor_msgs::Image message on success, or raises cv_bridge.CvBridgeError on failure.

imgmsg_to_cv2(img_msg, desired_encoding='passthrough')

Convert a sensor_msgs::Image message to an OpenCV cv::Mat.

Parameters:
  • img_msg – A sensor_msgs::Image message
  • desired_encoding –

    The encoding of the image data, one of the following strings:

    • "passthrough"
    • one of the standard strings in sensor_msgs/image_encodings.h
Return type:

cv::Mat
Raises:

CvBridgeError – when conversion is not possible.

If desired_encoding is "passthrough", then the returned image has the same format as img_msg. Otherwise desired_encoding must be one of the standard image encodings

This function returns an OpenCV cv::Mat message on success, or raises cv_bridge.CvBridgeError on failure.

If the image only has one channel, the shape has size 2 (width and height)

class cv_bridge.CvBridgeError

This is the error raised by cv_bridge.CvBridge methods when they fail.

Indices and tables