Raspicam_node md5sum error issue


I am running UbiquityRobotics latest image ( 2019-02-19-ubiquity-xenial-lxde) on a raspberry pi 3. I have set up pi camera v2 and it is streaming image. I can get the image on computer B using rqt_image_view. But, I am trying to write my own code on computer B to get image for doing image processing. Whenever I run my code, I get md5sum mismatch error. Here is a sample of the error:

[ERROR] [1559122373.331797723]: Client [/image_converter_14571_1559122369213] wants topic /raspicam_node/image/compressed to have datatype/md5sum [sensor_msgs/Image/060021388200f6f0f447d0fcd9c64743], but our version has [sensor_msgs/CompressedImage/8f7a12909da2c9d3332d540a0977563f]. Dropping connection.

I am also running ROS kinetic on computer B.

Here is my code. This is an example code I got online. May be something is wrong there. Please help me.

#!/usr/bin/env python
"""OpenCV feature detectors with ros CompressedImage Topics in python.

This example subscribes to a ros topic containing sensor_msgs 
CompressedImage. It converts the CompressedImage into a numpy.ndarray, 
then detects and marks features in that image. It finally displays 
and publishes the new image - again as CompressedImage topic.
__author__ =  'Simon Haller <simon.haller at uibk.ac.at>'
__version__=  '0.1'
__license__ = 'BSD'
# Python libs
import sys, time

# numpy and scipy
import numpy as np
from scipy.ndimage import filters

# OpenCV
import cv2

# Ros libraries
import roslib
import rospy

# Ros Messages
from sensor_msgs.msg import CompressedImage
# We do not use cv_bridge it does not support CompressedImage in python
# from cv_bridge import CvBridge, CvBridgeError


class image_feature:

    def __init__(self):
        '''Initialize ros publisher, ros subscriber'''
        # topic where we publish
        self.image_pub = rospy.Publisher("/output/image_raw/compressed",
        # self.bridge = CvBridge()

        # subscribed Topic
        self.subscriber = rospy.Subscriber("/raspicam_node/image/compressed",
            CompressedImage, self.callback,  queue_size = 1)
        if VERBOSE :
            print "subscribed to /camera/image/compressed"

    def callback(self, ros_data):
        '''Callback function of subscribed topic. 
        Here images get converted and features detected'''
        if VERBOSE :
            print 'received image of type: "%s"' % ros_data.format

        #### direct conversion to CV2 ####
        np_arr = np.fromstring(ros_data.data, np.uint8)
        image_np = cv2.imdecode(np_arr, cv2.CV_LOAD_IMAGE_COLOR)
        #### Feature detectors using CV2 #### 
        # "","Grid","Pyramid" + 
        # "FAST","GFTT","HARRIS","MSER","ORB","SIFT","STAR","SURF"
        method = "GridFAST"
        feat_det = cv2.FeatureDetector_create(method)
        time1 = time.time()

        # convert np image to grayscale
        featPoints = feat_det.detect(
            cv2.cvtColor(image_np, cv2.COLOR_BGR2GRAY))
        time2 = time.time()
        if VERBOSE :
            print '%s detector found: %s points in: %s sec.'%(method,

        for featpoint in featPoints:
            x,y = featpoint.pt
            cv2.circle(image_np,(int(x),int(y)), 3, (0,0,255), -1)
        cv2.imshow('cv_img', image_np)

        #### Create CompressedIamge ####
        msg = CompressedImage()
        msg.header.stamp = rospy.Time.now()
        msg.format = "jpeg"
        msg.data = np.array(cv2.imencode('.jpg', image_np)[1]).tostring()
        # Publish new image

def main(args):
    '''Initializes and cleanup ros node'''
    ic = image_feature()
    rospy.init_node('image_feature', anonymous=True)
    except KeyboardInterrupt:
        print "Shutting down ROS Image feature detector module"

if __name__ == '__main__':


Are you running some node named ‘image_converter’? That node is trying to subscribe to the raspicam data as a sensor_msgs/Image instead of a sensor_msgs/CompressedImage. The image_feature node you posted the code for doesn’t seem to have any issues.