Submission of Manoj Kumar 220625

Assignment 1/README.md

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+What I have done for this Assignment:
+
+#Learnt about openCv, classes, methods and about various dependencies to create/build a package.
+#Create a package named image_processes in catkin_ws/src folder by running command line in terminal as catkin_create-pkg image_processes rospy roscpp cv_bridge stdg_msgs and more.
+#Now run the catkin_make command in catkin_ws folder
+#now created the node1.py node2.py node3.py files in catkin_ws/src/image_processes/src path
+#now make the files executable by running command chmod +x node1.py and similarily for others two
+#in node1.py imports the required libraries and then created a webcam-pub function which open the camera gather the image data and then publish it to the Webcam
+-img topic
+#in node2.py I subscribed to Webcam_img topic then publish a Webcam_cropped topic which has the image data 30% reduced by pixels. To crop, first we have to convert Ros image into cv image then crop it again convert into Ros image.
+#in node3.py I subscribed the Webcam_cropped topic then show that cropped to image
+#Finally created a launch file which launches all the three nodes at once.
+
+
+
+#resources:-
+wiki.ros.org
+ChatGPT
+askubuntu.com
+stackoverflow.com

Assignment 1/launch/image_cropping.launch

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+<launch>
+  <!-- node tag used to launch a node. here it will launch node1 which is webcam_publisher.-->
+  <!-- pkg stores package name. type stores name of node file -->
+  <node name="webcam_publisher" pkg="image_processes" type="node1.py">
+
+    <param name="image_topic" value="webcam_image"/>
+  </node>
+
+  <!-- here it will launch the node2 which is image_cropper -->
+  <node name="image_cropper" pkg="image_processes" type="node2.py">
+
+    <param name="input_image_topic" value="webcam_image"/>
+    <param name="output_image_topic" value="cropped_image"/>
+  </node>
+
+  <!-- now final node3 will launch which is image_viewer node -->
+  <node name="image_viewer" pkg="image_processes" type="node3.py">
+
+    <param name="image_topic" value="cropped_image"/>
+  </node>
+</launch>

Assignment 1/src/node1.py

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+#!/usr/bin/env python3
+
+import rospy
+from sensor_msgs.msg import Image
+from cv_bridge import CvBridge
+import cv2
+
+def webcam_pub():
+    #To initialize the node
+    rospy.init_node('webcam_publisher', anonymous=True)
+    #Creating a publisher for the Webcam_image topic
+    image_publisher = rospy.Publisher('Webcam_img', Image, queue_size=10)
+    #publishing rate in Hz
+    rate = rospy.Rate(10)
+
+    #variable/objct to store CvBridge() class
+    bridge = CvBridge()
+    #it will open camera
+    camera = cv2.VideoCapture(0)
+
+    while not rospy.is_shutdown():
+        #it will capture frames
+        ret, frame = camera.read()
+
+        if ret:
+            try:
+                #converts image to ros msg
+                image_msg = bridge.cv2_to_imgmsg(frame, "bgr8")
+                #publish the image message
+                image_publisher.publish(image_msg)
+            except Exception as e:
+                rospy.logerr(e)
+
+        #It will maintain the publishing rate by sleeping
+        rate.sleep()
+
+    camera.release()
+
+if __name__ == '__main__':
+    try:
+        webcam_pub()
+    except rospy.ROSInterruptException:
+        pass

Assignment 1/src/node2.py

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+#!/usr/bin/env python3
+
+import rospy
+from sensor_msgs.msg import Image
+from cv_bridge import CvBridge
+import cv2
+
+image_publisher = None
+
+def img_callback(msg):
+    global image_publisher
+
+    try:
+        #now convert the ros image into cv image
+        bridge = CvBridge()
+        cv_image = bridge.imgmsg_to_cv2(msg, "bgr8")
+
+        #cropping by 30% pixels [y1:y2, x1:x2] where (x1,y1) is the coordinate of bottom left corner and (x2,y2) is of top right corner
+        cropped_image = cv_image[108:396, 192:1088]
+        #again converting cv image to ros image message
+        cropped_msg = bridge.cv2_to_imgmsg(cropped_image, "bgr8")
+
+        #publishes the cropped image
+        image_publisher.publish(cropped_msg)
+
+    except Exception as e:
+        rospy.logerr(e)
+
+def img_cropper():
+    global image_publisher
+
+    #init_node command to initialize the node
+    rospy.init_node('image_cropper', anonymous=True)
+
+    #Creating a publisher for the cropped image topic
+    image_publisher = rospy.Publisher('Webcam_cropped', Image, queue_size=10)
+
+    # Creating a subscriber for the image topic
+    rospy.Subscriber('Webcam_img', Image, img_callback)
+
+    rospy.spin()
+
+if __name__ == '__main__':
+    try:
+        img_cropper()
+    except rospy.ROSInterruptException:
+        pass

Assignment 1/src/node3.py

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+#!/usr/bin/env python3
+
+import rospy
+from sensor_msgs.msg import Image
+from cv_bridge import CvBridge
+import cv2
+
+def image_callback(msg):
+    try:
+        #converting the ros image message to opencv format
+        bridge = CvBridge()
+        cv_image = bridge.imgmsg_to_cv2(msg, "bgr8")
+
+        #displays the cropped image
+        cv2.imshow("Webcam-Cropped-Image", cv_image)
+        cv2.waitKey(1)  #Refresh display every 1 ms
+
+    except Exception as e:
+        rospy.logerr(e)
+
+def image_viewer():
+    #initializing the node
+    rospy.init_node('image_viewer', anonymous=True)
+
+    #Creating a subscriber for the image topic
+    rospy.Subscriber('Webcam_cropped', Image, image_callback)
+
+    rospy.spin()
+
+    cv2.destroyAllWindows()
+
+if __name__ == '__main__':
+    try:
+        image_viewer()
+    except rospy.ROSInterruptException:
+        pass