OpenCV4.2 and Ubuntu16.04 with python2.7?

[Algabri]

I tried to build cv_bridge in order to run OpenCV 4.2, Ubuntu 16.04 (ROS Kinetic) and python 2.7.

I will explain what I do for that.

I built it before with OpenCV 3.3.1 in order to use GPU and it was very fine and it is still working now. To best my knowledge, there is ros-kinetic-opencv3 , it is working only on CPU. I removed it using sudo apt remove ros-kinetic-opencv3

After removing, I just downloaded your here and put in my ~/catkin_ws/src/, then making ~/catkin_ws/catkin_make on my PC without any modifications. I think that I was lucky.

Now, I'd like use some advantage of OpenCV 4.2 that is not with older versions like OpenCV 3.3.1. Meanwhile, I can't update robot's system, it is Ubuntu 16.04.

So, I tried to build cv_bridge, all modifications as following:

I copied and pasted module_opencv3.cpp, then change its name to module_opencv4.cpp so that became three models 4, 3 and 2.cpp instead of two 3 and 2.cpp.
Next , Sreevan mentioned here some changes, I did like Sreevan:

In cv_bridge/src/module_opencv3.cpp change signature of two functions
3.1) UMatData* allocate(int dims0, const int* sizes, int type, void* data, size_t* step, int flags, UMatUsageFlags usageFlags) const
to
UMatData* allocate(int dims0, const int* sizes, int type, void* data, size_t* step, AccessFlag flags, UMatUsageFlags usageFlags) const
3.2) bool allocate(UMatData* u, int accessFlags, UMatUsageFlags usageFlags) const
to
bool allocate(UMatData* u, AccessFlag accessFlags, UMatUsageFlags usageFlags) const

Next, I went to this file ~/catkin_ws/src/vision_opencv/cv_bridge$ CMakeLists.txt and change it as:
from:

find_package(OpenCV 3 REQUIRED
  COMPONENTS
    opencv_core
    opencv_imgproc
    opencv_imgcodecs
  PATHS /usr/local
  NO_DEFAULT_PATH
  CONFIG
)

to:

if ( NOT (OpenCV_VERSION_MAJOR VERSION_LESS 4) )
find_package(OpenCV REQUIRED
  COMPONENTS
    opencv_core
    opencv_imgproc
    opencv_imgcodecs
  #PATHS /usr/local/include
  PATHS /usr/local
  NO_DEFAULT_PATH
  CONFIG
)
else()
find_package(OpenCV 3 REQUIRED
  COMPONENTS
    opencv_core
    opencv_imgproc
    opencv_imgcodecs
  PATHS /usr/local
  NO_DEFAULT_PATH
  CONFIG
)
endif()

Next, I went to this file ~/catkin_ws/src/vision_opencv/cv_bridge/src$ CMakeLists.txt and change it as:
from:

if (OpenCV_VERSION_MAJOR VERSION_EQUAL 3)
add_library(${PROJECT_NAME}_boost module.cpp module_opencv3.cpp)
else()
add_library(${PROJECT_NAME}_boost module.cpp module_opencv2.cpp)
endif()

to

if (OpenCV_VERSION_MAJOR VERSION_EQUAL 4)
  add_library(${PROJECT_NAME}_boost module.cpp module_opencv4.cpp)
elseif(OpenCV_VERSION_MAJOR VERSION_EQUAL 3)
  add_library(${PROJECT_NAME}_boost module.cpp module_opencv3.cpp)
else()
  add_library(${PROJECT_NAME}_boost module.cpp module_opencv2.cpp)
endif()

Next, I think this step is not important, I went to this file ~/catkin_ws/src/vision_opencv/cv_bridge$ package.xml and change any opencv3 to opencv4

Finally, ~/catkin_ws$ catkin_make

everything was ok but when I run the code:

import rospy
import cv2
import numpy as np
from sensor_msgs.msg import Image
from cv_bridge import CvBridge, CvBridgeError

print(cv2.__version__)

class CVControl:
    def __init__(self):
        self.bridge = CvBridge()
        self.image_sub = rospy.Subscriber("/camera/rgb/image_raw", Image, self.img_callback)
    def img_callback(self, data):
        try:
            cv_image = self.bridge.imgmsg_to_cv2(data, "bgr8")
        except CvBridgeError as e:
            print e

        frame = cv_image
        cv2.imshow("Image window", frame)
        cv2.waitKey(3)
def main():
    ctrl = CVControl()
    rospy.init_node('image_converter')
    try:
        rospy.spin()

    except KeyboardInterrupt:
        print "Shutting down"
        cv2.destroyAllWindows()

if __name__ == '__main__':
    main()

It runs by OpenCV 3.3.1

If I need to run it by OpenCV 4.2
I added those lines in first the code:

import sys
ros_path2 = '/usr/local/lib/python2.7/site-packages'
ros_path3 = '/usr/lib/python2.7/dist-packages'
if  ros_path2 and ros_path3 in sys.path:
    sys.path.remove(ros_path2)
    sys.path.remove(ros_path3)

The output is:

import rospkg
ImportError: No module named rospkg

What is wrong?

It is possible to run it by OpenCV or not?? If yes, it is easy or difficult??
I read some answer, someone said " it is impossible"

Please your opinions or any suggestions?

[ijnek]

Hi @Algabri, I just came maintainer of this repo and I'm sorry this issue didn't get a response previously. As this is related to ROS Kinetic which has reached EOL, I'm going to close the issue. Please feel free to re-open it if the problem persists in the active distributions. Thanks!