Added template node for capturing data from a camera and saving images to file

catkin_ws/src/asclinic_pkg/launch/template_camera_capture.launch

+<launch>
+	<group ns="template_camera">
+		<node
+			pkg    = "asclinic_pkg"
+			name   = "template_camera_capture"
+			output = "screen"
+			type   = "template_camera_capture.py"
+		/>
+	</group>
+</launch>

catkin_ws/src/asclinic_pkg/src/nodes/template_camera_capture.py

+#!/usr/bin/env python3
+# -*- coding: utf-8 -*-
+
+# Copyright (C) 2021, The University of Melbourne, Department of Electrical and Electronic Engineering (EEE)
+#
+# This file is part of ASClinic-System.
+#    
+# See the root of the repository for license details.
+#
+# ----------------------------------------------------------------------------
+#     _    ____   ____ _ _       _          ____            _                 
+#    / \  / ___| / ___| (_)____ (_) ___    / ___| _   _ ___| |_ ___ ________  
+#   / _ \ \___ \| |   | | |  _ \| |/ __|___\___ \| | | / __| __/ _ \  _   _ \ 
+#  / ___ \ ___) | |___| | | | | | | (_|_____|__) | |_| \__ \ ||  __/ | | | | |
+# /_/   \_\____/ \____|_|_|_| |_|_|\___|   |____/ \__, |___/\__\___|_| |_| |_|
+#                                                 |___/                       
+#
+# DESCRIPTION:
+# Template Python node to capture and publish video
+#
+# ----------------------------------------------------------------------------
+
+# Import the ROS-Python package
+import rospy
+#import rospkg
+
+# Import the standard message types
+from std_msgs.msg import UInt32
+from sensor_msgs.msg import Image
+
+# Import opencv
+import cv2
+
+# Package to convert between ROS and OpenCV Images
+from cv_bridge import CvBridge
+
+
+
+# DEFINE THE PARAMETERS
+# > For the number of the USB camera device
+#   i.e., for /dev/video0, this parameter should be 0
+USB_CAMERA_DEVICE_NUMBER = 0
+
+# > For where to save images captured by the camera
+#   Note: ensure that this path already exists
+#   Note: images are only saved when a message is received
+#         on the "request_save_image" topic.
+SAVE_IMAGE_PATH = "/home/asc01/saved_camera_images/"
+
+# > A flag for whether to display the images captured
+SHOULD_SHOW_IMAGES = False
+
+
+
+class TemplateCameraCapture:
+
+    def __init__(self):
+        
+        # Initialise a publisher for the images
+        self.image_publisher = rospy.Publisher("/global_namespace"+"/camera_image", Image, queue_size=10)
+
+        # Initialise a subscriber for flagging when to save an image
+        rospy.Subscriber("/global_namespace"+"/request_save_image", UInt32, self.requestSaveImageSubscriberCallback)
+        # > For convenience, the command line can be used to trigger this subscriber
+        #   by publishing a message to the "request_save_image" as follows:
+        #
+        # rostopic pub /global_namespace/request_save_image std_msgs/UInt32 "data: 1" 
+
+        # Initialise varaibles for managing the saving of an image
+        self.save_image_counter = 0
+        self.should_save_image = False
+
+        # Specify the details for camera to capture from
+        
+        # > For capturing from a USB camera:
+        self.camera_setup = USB_CAMERA_DEVICE_NUMBER
+        
+        # > For capturing from the CSI camera port:
+        #   > Gstreamer for capture video
+        #   > sensor-id=0 for CAM0 and sensor-id=1 for CAM1
+        #   > This is not optimized, but it does work.
+        #self.camera_setup = 'nvarguscamerasrc sensor-id=0 ! video/x-raw(memory:NVMM), width=3264, height=2464, framerate=12/1, format=NV12 ! nvvidconv flip-method=0 ! video/x-raw, width = 800, height=600, format =BGRx ! videoconvert ! video/x-raw, format=BGR ! appsink'
+
+        # Initialise video capture from the camera
+        self.cam=cv2.VideoCapture(self.camera_setup)
+
+        # Initlaise the OpenCV<->ROS bridge
+        self.cv_bridge = CvBridge()
+
+        # Display the status
+        rospy.loginfo("[TEMPLATE CAMERA CAPTURE] Initialisation complete")
+
+        # Initialise a timer for capturing the camera frames
+        rospy.Timer(rospy.Duration(3.0), self.timerCallbackForPublishing)
+
+
+
+    # Respond to timer callback
+    def timerCallbackForPublishing(self, event):
+        # Read the camera frame
+        rospy.loginfo('[TEMPLATE CAMERA CAPTURE] Now reading camera frame')
+        return_flag , current_frame = self.cam.read()
+
+        # Check if the camera frame was successfully read
+        if (return_flag == True):
+            # Publish the camera frame
+            rospy.loginfo('[TEMPLATE CAMERA CAPTURE] Now publishing camera frame')
+            self.image_publisher.publish(self.cv_bridge.cv2_to_imgmsg(current_frame))
+            # Save the camera frame if requested
+            if (self.should_save_image):
+                # Increment the image counter
+                self.save_image_counter += 1
+                # Write the image to file
+                temp_filename = SAVE_IMAGE_PATH + "image" + str(self.save_image_counter) + ".jpg"
+                cv2.imwrite(temp_filename,current_frame)
+                # Display the path to where the image was saved
+                rospy.loginfo("[TEMPLATE CAMERA CAPTURE] Save camera frame to: " + temp_filename)
+                # Reset the flag to false
+                self.should_save_image = False
+
+            # Display the camera frame
+            if (SHOULD_SHOW_IMAGES):
+                rospy.loginfo("[TEMPATE CAMERA CAPTURE] Now displaying camera frame")
+                cv2.imshow("CAM 0", current_frame)
+        else:
+            # Display an error message
+            rospy.loginfo('[TEMPLATE CAMERA CAPTURE] ERROR occurred during self.cam.read()')
+
+
+
+    # Respond to subscriber receiving a message
+    def requestSaveImageSubscriberCallback(self, msg):
+        rospy.loginfo("[TEMPLATE CAMERA CAPTURE] Request receieved to save the next image")
+        # Set the flag for saving an image
+        self.should_save_image = True
+
+
+
+if __name__ == '__main__':
+    # Initialise the node
+    global node_name
+    node_name = "template_camera_capture"
+    rospy.init_node(node_name)
+    template_camera_capture = TemplateCameraCapture()
+    # Spin as a single-threaded node
+    rospy.spin()