For my class robotics project, we are required to read in video feed frame by frame from a virtual turtlebot being simulated using gazebo. Then we detect colors in this image (red, blue, and green) if they are at the center of the image, within a rectangle that we have to draw in the center of the frame. If one of the colors are detected, the rectangle should change from green to red, and if the 's' button is clicked while the rectangle is red (ie it detects a color) then it should publish to a topic saying that the target was shot. The majority of this code was written for a previous assignment, in which we had to detect any of these colors anywhere in a frame from a webcam and indicate it with a bounding box or circle, and my code worked for that assignment. Now I have changed my code slightly to read frames from the virtual camera, and I added some code from some example code that our professor provided us with to try to publish the modified image so that I can view it using Rviz. Whatever I added is making the code no longer work as it should and I am getting an error, but I don't understand the code deeply enough to find my error.
The error that I am receiving is as follows:
[ERROR] [1575253473.863051, 2724.055000]: bad callback:
Traceback (most recent call last):
File "/opt/ros/melodic/lib/python2.7/dist-packages/rospy/topics.py", line 750, in _invoke_callback cb(msg)
File "/home/project_ws/src/project_gazebo/scripts/color_detect.py", line 49, in ImageCallback upper_left(int(w/4), h)
TypeError: 'NoneType' object is not callable
I have no idea what this means or how to fix it. I know that it is probably a problem with the subscriber callback function, but I tried to write it exactly how the professor's example did for face detection (rather than color detection). Other than that, I have no idea how to fix this issue. I could really use some guidance.
Here is what the file looks like (I would only post a snippet, but since I am unsure where the issue is I am posting all of it):
#!/usr/bin/env python
from __future__ import print_function
from collections import deque
import numpy as np
import cv2
import sys
import rospy
import rospkg
from std_msgs.msg import String
from sensor_msgs.msg import Image
from cv_bridge import CvBridge, CvBridgeError
hit_pub = rospy.Publisher('Cait/hit', String, queue_size=10)
image_pub = rospy.Publisher("Cait/image_topic_2",Image, queue_size=10)
bridge = CvBridge()
frame = None
height= None
width= None
upper_left=None
lower_right=None
inRange= False
targetHit = False
def ImageCallback(data):
try:
global frame
frame = bridge.imgmsg_to_cv2(data, "bgr8")
#frame = data.data
global height
global width
(h, w) = frame.shape[:2] #w:image-width and h:image-height
height = h
width = w
global centerPoint_x
global centerPoint_y
centerPoint_x = w/2
centerpoint_y= h/2
global upper_left
global lower_right
upper_left(int(w/4), h)
lower_right(int(w*3/4), 0)
except CvBridgeError as e:
print(e)
image_sub = rospy.Subscriber("Cait/camera/rgb/image_raw",Image,ImageCallback)
def Image_converter():
# define the lower and upper boundaries of the colors in the HSV color space
lower = {'red':(166, 84, 141), 'green':(66, 122, 129), 'yellow':(23, 59, 119)}
upper = {'red':(186,255,255), 'green':(86,255,255), 'yellow':(54,255,255)}
# grab frames from webcam -> now grab fromm rviz raw_image in subscriber
#camera = cv2.VideoCapture(0)
# keep looping
while True:
# grab the current frame -> now done by ImageCallback()
#(grabbed, frame) = camera.read()
hsv = cv2.cvtColor(frame, cv2.COLOR_BGR2HSV)
#for each color in dictionary check object in frame
#draw rectangle in the center of the frame
cv2.rectangle(frame, upper_left, lower_right, (0, 255, 0), 2)
for key, value in upper.items():
# construct a mask for the color from dictionary`1, then remove any small blobs left in the mask
kernel = np.ones((9,9),np.uint8)
mask = cv2.inRange(hsv, lower[key], upper[key])
mask = cv2.morphologyEx(mask, cv2.MORPH_OPEN, kernel)
mask = cv2.morphologyEx(mask, cv2.MORPH_CLOSE, kernel)
# find contours in the mask and initialize the current (x, y) center of the ball
cnts = cv2.findContours(mask.copy(), cv2.RETR_EXTERNAL,
cv2.CHAIN_APPROX_SIMPLE)[-2]
center = None
# only proceed if at least one contour was found
if len(cnts) > 0:
# find the largest contour in the mask, then use it to compute the minimum enclosing circle
c = max(cnts, key=cv2.contourArea)
((x, y), radius) = cv2.minEnclosingCircle(c)
#check to see if the point found is at the center of the screen, and if yes change the color of the rectangle
global inRange
if (x > int(width/4) & x< int(width*3/4)):
if(y > 0 & y < height):
cv2.rectangle(frame, upper_left, lower_right, (0, 0, 255), 2)
inRange = True
else:
cv2.rectangle(frame, upper_left, lower_right, (0, 255, 0), 2)
inRange= False
# show the frame to our screen
cv2.imshow("Image window", frame)
key = cv2.waitKey(1) & 0xFF
try:
image_pub.publish(bridge.cv2_to_imgmsg(frame, "bgr8"))
except CvBridgeError as e:
print(e)
# if the 's' key is pressed, publish an answer to the topic
if key == ord("s"):
if (inRange):
hit_pub.publish("Target hit!")
else:
hit_pub.publish("Sorry. Nothing was hit.")
if key == ord("q"): #q quits loop
break
def main(args):
rospy.init_node('image_converter', anonymous=True)
Image_converter()
try:
rospy.spin()
except KeyboardInterrupt:
print("Shutting down")
cv2.destroyAllWindows()
if __name__ == '__main__':
main(sys.argv)
