cv_corner.py

#!/usr/bin/env python
from __future__ import print_function

import roslib
#roslib.load_manifest('my_package')
import sys
import rospy
import cv2
from std_msgs.msg import String
from sensor_msgs.msg import Image
from cv_bridge import CvBridge, CvBridgeError
import numpy as np
import matplotlib.pyplot as plt


class image_converter:

  def __init__(self):
    self.image_pub = rospy.Publisher("image_topic_2",Image)

    self.bridge = CvBridge()
    self.image_sub = rospy.Subscriber("/camera/rgb/image_color",Image,self.callback)

  def callback(self,data):
    try:
      cv_image = self.bridge.imgmsg_to_cv2(data, "bgr8")
      #img = cv2.imread(cv_image)
      gray = cv2.cvtColor(cv_image,cv2.COLOR_BGR2GRAY)

      gray = np.float32(gray)
      dst = cv2.cornerHarris(gray,2,3,0.04)

      #result is dilated for marking the corners, not important
      dst = cv2.dilate(dst,None)


      # Threshold for an optimal value, it may vary depending on the image.

      cv_image[dst>0.01*dst.max()]=[0,0,255]



      #plt.imshow(cv_image)
      #print(img)
      #plt.show()
      cv2.imshow('cv_image',1)


    except CvBridgeError as e:
      print(e)

    (rows,cols,channels) = cv_image.shape
    if cols > 60 and rows > 60 :
      cv2.circle(cv_image, (50,50), 10, 255)

    cv2.imshow("Image window", cv_image)
    cv2.waitKey(3)

    try:
      self.image_pub.publish(self.bridge.cv2_to_imgmsg(cv_image, "bgr8"))
    except CvBridgeError as e:
      print(e)

def main(args):
  ic = image_converter()
  rospy.init_node('image_converter', anonymous=True)
  try:
    rospy.spin()
  except KeyboardInterrupt:
    print("Shutting down")
  cv2.destroyAllWindows()

if __name__ == '__main__':
    main(sys.argv)