Ask Your Question
0

cv_bridge not showing RGB image [closed]

asked 2021-02-11 16:52:49 -0500

murilosantos gravatar image

updated 2021-02-11 16:56:16 -0500

I am following the steps from a Book, for setting up OpenCV to work together ROS through cv_bridge. The book is a bit old, and the original code was a legacy python2 code. The Camera is a Kinect V1.

I used 2to3 to convert it to python3, and after several runs catching the error codes and updating (or trying to) to new OpenCV commands I got it running,

But in the book, says it was supposed to show 3 windows: RBG, Depth and Edges.

When I run my "adjusted" code, it only shows Depth and Edges. Would somebody know what is missing on it?

# This is the original Code

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

class cvBridgeDemo():
    def __init__(self):
        self.node_name = "cv_bridge_demo"
        #Initialize the ros node
        rospy.init_node(self.node_name)

        # What we do during shutdown
        rospy.on_shutdown(self.cleanup)

        # Create the OpenCV display window for the RGB image
        self.cv_window_name = self.node_name
        cv.NamedWindow(self.cv_window_name, cv.CV_WINDOW_NORMAL)
        cv.MoveWindow(self.cv_window_name, 25, 75)

        # And one for the depth image
        cv.NamedWindow("Depth Image", cv.CV_WINDOW_NORMAL)
        cv.MoveWindow("Depth Image", 25, 350)

        # Create the cv_bridge object
        self.bridge = CvBridge()

        # Subscribe to the camera image and depth topics and set
        # the appropriate callbacks
        self.image_sub = rospy.Subscriber("/camera/rgb/image_color", Image,self.image_callback)
        self.depth_sub = rospy.Subscriber("/camera/depth/image_raw", Image,self.depth_callback)
        rospy.loginfo("Waiting for image topics...")

    def image_callback(self, ros_image):

        # Use cv_bridge() to convert the ROS image to OpenCV format
        try:
            frame = self.bridge.imgmsg_to_cv(ros_image, "bgr8")
        except CvBridgeError, e:
            print e
        # Convert the image to a Numpy array since most cv2 functions

        # require Numpy arrays.
        frame = np.array(frame, dtype=np.uint8)

        # Process the frame using the process_image() function
        display_image = self.process_image(frame)

        # Display the image.
        cv2.imshow(self.node_name, display_image)

        # Process any keyboard commands
        self.keystroke = cv.WaitKey(5)
        if 32 <= self.keystroke and self.keystroke < 128:
            cc = chr(self.keystroke).lower()
            if cc == 'q':
                # The user has press the q key, so exit
                rospy.signal_shutdown("User hit q key to quit.")

    def depth_callback(self, ros_image):
        # Use cv_bridge() to convert the ROS image to OpenCV format
        try:
            # The depth image is a single-channel float32 image
            depth_image = self.bridge.imgmsg_to_cv(ros_image,"32FC1")
        except CvBridgeError, e:
            print e
        # Convert the depth image to a Numpy array since most cv2 functions

        # require Numpy arrays.
        depth_array = np.array(depth_image, dtype=np.float32)
        # Normalize the depth image to fall between 0 (black) and 1 (white)
        cv2.normalize(depth_array,depth_array, 0, 1, cv2.NORM_MINMAX)
        # Process the depth image
        depth_display_image = self.process_depth_image(depth_array)

        # Display the result
        cv2.imshow("Depth Image", depth_display_image)


    def process_image(self, frame):
        # Convert to grayscale
        grey = cv2.cvtColor(frame, cv.CV_BGR2GRAY)
        # Blur the image
        grey = cv2.blur(grey, (7, 7))

        # Compute edges using the Canny edge filter
        edges = cv2.Canny(grey, 15.0, 30.0)
        return edges


    def process_depth_image(self, frame):
        # Just return the raw image for ...
(more)
edit retag flag offensive reopen merge delete

Closed for the following reason the question is answered, right answer was accepted by murilosantos
close date 2021-02-15 13:36:55.072637

Comments

1

I only see two instances each of imshow() and namedWindow() , so I'm not sure why three images are expected--even in the original code. In image_callback(), the BGR image is processed (self.process_image()) into a Canny edge image before display. If you want to see the color image, you'll have to add an extra display.

tryan gravatar image tryan  ( 2021-02-12 09:24:58 -0500 )edit
1

@tryan That was my feeling too. I got reading again a few times to ensure is nothing missing in that example... This is wahy I asked before concluding with my low-level about openCV. Perhaps the editors have missed something. I will try to add it and see how it goes.

murilosantos gravatar image murilosantos  ( 2021-02-13 06:37:11 -0500 )edit

1 Answer

Sort by ยป oldest newest most voted
1

answered 2021-02-15 13:18:06 -0500

murilosantos gravatar image

updated 2021-02-15 13:18:34 -0500

tryan's comment was actually the answer. I could manage to fix it by adding the following lines:

In the _____init_____ func:

cv2.namedWindow('Image RBG', cv2.WINDOW_NORMAL)
cv2.moveWindow('Image RBG', 25, 350)

And in the callback func:

cv2.imshow('Image RBG', frame)
edit flag offensive delete link more

Question Tools

1 follower

Stats

Asked: 2021-02-11 16:52:49 -0500

Seen: 136 times

Last updated: Feb 15