contour_mapping.py

import cv2
import numpy as np

cap = cv2.VideoCapture(0)

while( cap.isOpened() ) :
    ret,img = cap.read()
    gray = cv2.cvtColor(img,cv2.COLOR_BGR2GRAY)
    blur = cv2.GaussianBlur(gray,(5,5),0)
    ret,thresh1 = cv2.threshold(blur,70,255,cv2.THRESH_BINARY_INV+cv2.THRESH_OTSU)
  
    contours, hierarchy = cv2.findContours(thresh1,cv2.RETR_TREE,cv2.CHAIN_APPROX_SIMPLE)
    drawing = np.zeros(img.shape,np.uint8)

    max_area=0
   
    for i in range(len(contours)):
            cnt=contours[i]
            area = cv2.contourArea(cnt)
            if(area>max_area):
                max_area=area
                ci=i
    cnt=contours[ci]
    hull = cv2.convexHull(cnt)
    moments = cv2.moments(cnt)
    if moments['m00']!=0:
                cx = int(moments['m10']/moments['m00']) # cx = M10/M00
                cy = int(moments['m01']/moments['m00']) # cy = M01/M00
              
    centr=(cx,cy)       
    cv2.circle(img,centr,5,[0,0,255],2)       
    cv2.drawContours(drawing,[cnt],0,(0,255,0),2) 
    cv2.drawContours(drawing,[hull],0,(0,0,255),2) 
          
    cnt = cv2.approxPolyDP(cnt,0.01*cv2.arcLength(cnt,True),True)
    hull = cv2.convexHull(cnt,returnPoints = False)
    
   
    cv2.imshow('output',drawing)
    cv2.imshow('input',img)
                
    k = cv2.waitKey(10) % 0x100
    if k == 27:
        break