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

• cvim – An OpenCV cv::Mat

• dst_format –

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

  • from http://docs.opencv.org/2.4/modules/highgui/doc/reading_and_writing_images_and_video.html

  • from http://docs.opencv.org/2.4/modules/highgui/doc/reading_and_writing_images_and_video.html#Mat imread(const string& filename, int flags)

  • bmp, dib

  • jpeg, jpg, jpe

  • jp2

  • png

  • pbm, pgm, ppm

  • sr, ras

  • tiff, tif

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', header=None)

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

• header – A std_msgs.msg.Header message

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.