color_track_opencv.py

#
#Developed by Vikrant Fernandes
#

import numpy as np
import cv2
import serial

#Serial object for communication with Arduino
ser = serial.Serial('/dev/ttyACM0')

#Capture from external USB webcam instead of the in-built webcam (shitty quality)
cap = cv2.VideoCapture(1)

#kernel window for morphological operations
kernel = np.ones((5,5),np.uint8)

#resize the capture window to 640 x 480
ret = cap.set(3,640)
ret = cap.set(4,480)

#upper and lower limits for the color yellow in HSV color space
lower_yellow = np.array([20,100,100])
upper_yellow = np.array([30,255,255])

#begin capture
while(True):
    ret, frame = cap.read()

    #Smooth the frame
    frame = cv2.GaussianBlur(frame,(11,11),0)

    #Convert to HSV color space
    hsv = cv2.cvtColor(frame, cv2.COLOR_BGR2HSV)

    #Mask to extract just the yellow pixels
    mask = cv2.inRange(hsv,lower_yellow,upper_yellow)

    #morphological opening
    mask = cv2.erode(mask,kernel,iterations=2)
    mask = cv2.dilate(mask,kernel,iterations=2)

    #morphological closing
    mask = cv2.dilate(mask,kernel,iterations=2)
    mask = cv2.erode(mask,kernel,iterations=2)

    #Detect contours from the mask
    cnts = cv2.findContours(mask.copy(), cv2.RETR_EXTERNAL,
		cv2.CHAIN_APPROX_SIMPLE)[-2]

    if(len(cnts) > 0):
        #Contour with greatest area
        c = max(cnts,key=cv2.contourArea)
        #Radius and center pixel coordinate of the largest contour
        ((x,y),radius) = cv2.minEnclosingCircle(c)

        if radius > 5:
            #Draw an enclosing circle
            cv2.circle(frame,(int(x), int(y)), int(radius),(0, 255, 255), 2)

            #Draw a line from the center of the frame to the center of the contour
            cv2.line(frame,(320,240),(int(x), int(y)),(0, 0, 255), 1)
            #Reference line
            cv2.line(frame,(320,0),(320,480),(0,255,0),1)

            radius = int(radius)

            #distance of the 'x' coordinate from the center of the frame
            #wdith of frame is 640, hence 320
            length = 320-(int(x))

            #write distance and radius to Arduino through Serial Communication
            ser.write(str(length))
            ser.write('#')
            ser.write(str(radius))
            ser.write('/')

    #display the image
    cv2.imshow('frame',frame)
    #Mask image
    cv2.imshow('mask',mask)
    #Quit if user presses 'q'
    if cv2.waitKey(30) & 0xFF == ord('q'):
        break

#Release the capture
cap.release()
cv2.destroyAllWindows()