''' file name : findcontours.py

Description : This sample shows how to find and draw contours

This is Python version of this tutorial : http://opencv.itseez.com/doc/tutorials/imgproc/shapedescriptors/find_contours/find_contours.html#find-contours

Level : Beginner

Benefits : Learn to use 1) cv2.findContours() and 2)cv2.drawContours()

Usage : python findcontours.py

Written by : Abid K. (abidrahman2@gmail.com) , Visit opencvpython.blogspot.com for more tutorials'''

import cv2
import numpy as np

def thresh_callback(thresh):
    edges = cv2.Canny(blur,thresh,thresh*2)
    drawing = np.zeros(img.shape,np.uint8) # Image to draw the contours
    contours,hierarchy = cv2.findContours(edges,cv2.RETR_LIST,cv2.CHAIN_APPROX_SIMPLE)
    maxPerimetro=0
    for cnt in contours:
	M = cv2.moments(cnt)
	perimeter = cv2.arcLength(cnt,True)
	if perimeter > maxPerimetro:
		maxPerimetro=perimeter
		contornomayor = cnt
		print maxPerimetro

    
    color = np.random.randint(250,255,(3)).tolist() # Select a random color
    cv2.drawContours(drawing,[contornomayor],0,color,1)
    cv2.imshow('output',drawing)
    cv2.imshow('input',img)

img = cv2.imread('guitarra.jpg')
gray = cv2.cvtColor(img,cv2.COLOR_BGR2GRAY)
blur = cv2.GaussianBlur(gray,(5,5),0)

cv2.namedWindow('input',cv2.WINDOW_AUTOSIZE)

thresh = 100
max_thresh = 255

cv2.createTrackbar('canny thresh:','input',thresh,max_thresh,thresh_callback)

thresh_callback(thresh)

if cv2.waitKey(0) == 27:
    cv2.destroyAllWindows()