ROS-Noetic OpenCV/AR Tag Detection

Question

I found this code in blog about OpenCV and i rewrite for using ROS gazebo simulation. I got many error about marker`finding. I will add the error below.

#!/usr/bin/env python3
# -*- coding: utf-8 -*-

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


class Camera():
    def __init__(self):
        rospy.init_node("camera_node")
        self.bridge = CvBridge()
        rospy.Subscriber("camera/rgb/image_raw", Image, self.cameraCallback)
        self.distance_to_camera()
        rospy.spin()
        
    def cameraCallback(self, message):
        try:
            cv_image = self.bridge.imgmsg_to_cv2(message, desired_encoding="bgr8")
        except Exception as e:
            rospy.logerr("Error converting Image message to CV2: {}".format(e))
            return None
     
    # convert the image to grayscale, blur it, and detect edges
        gray = cv2.cvtColor(cv_image, cv2.COLOR_BGR2GRAY)
        gray = cv2.GaussianBlur(gray, (5, 5), 0)
        edged = cv2.Canny(gray, 35, 125)
    
    # find the contours in the edged image and keep the largest one;
    # we'll assume that this is our piece of paper in the image
        cnts = cv2.findContours(edged.copy(), cv2.RETR_LIST, cv2.CHAIN_APPROX_SIMPLE)
        cnts = imutils.grab_contours(cnts)
    
        if len(cnts) == 0:
            rospy.logerr("No contour found in the image.")
            return None
    
        c = max(cnts, key=cv2.contourArea)
    
        cv2.imshow("edged", edged)
        cv2.imshow("camera", cv_image)
        cv2.waitKey(1)
    
    # compute the bounding box of the paper region and return it
        return cv2.minAreaRect(c)

    
    def distance_to_camera(self):
        KNOWN_DISTANCE = 3
        KNOWN_WIDTH = 0.3
    
        image = cv2.imread("distance.png")
        marker = self.cameraCallback(image)
    
        if marker is None:
            rospy.logerr("No marker found in the image.")
            return
    
        focalLength = (marker[1][0] * KNOWN_DISTANCE) / KNOWN_WIDTH
    # compute and return the distance from the maker to the camera
        
    
    
    
    # loop over the images
        for imagePath in sorted(paths.list_images("images")):
     # load the image, find the marker in the image, then compute the
     # distance to the marker from the camera
             image = cv2.imread(imagePath)
             marker = self.cameraCallback(image)
             inches = self.distance_to_camera(KNOWN_WIDTH, focalLength, marker[1][0])
    # draw a bounding box around the image and display it
             """box = cv2.BoxPoints(marker) if imutils.is_cv2() else cv2.boxPoints(marker)
             box = np.int0(box)
         
             cv2.drawContours(image, [box], -1, (0, 255, 0), 2)
         
             cv2.putText(image, "%.2fft" % (inches / 12),(image.shape[1] - 200, image.shape[0] - 20), cv2.FONT_HERSHEY_SIMPLEX,
        2.0, (0, 255, 0), 3)"""
         
             cv2.imshow("image", image)
         
             cv2.waitKey(0)
    

if __name__ == '__main__':
    
# cam = Camera()

[ERROR] : Error converting Image message to CV2: 'numpy.ndarray' object has no attribute 'encoding'
[ERROR] : No marker found in the image.

Thank you...

I want to apply image process for camera id which is come to gazebo turtlebot3 waffle pi. Afetr the apply image process, i expect the robot camera detect the AR Tag and measure the distance between robot and AR Tag sticker.