main.py

import os, math
import numpy as np
#from matplotlib import pyplot as plt
import cv2

img = cv2.resize(cv2.imread('img.jpg',1), (0,0), fx=0.5, fy=0.5)

def sort_cw(points):
    points = sorted(points,key=lambda cnt: cnt[0][0])
    
    left = points[:2]
    left_sorted = sorted(left,key=lambda cnt: cnt[0][1])
    top_left = left_sorted[0]
    bottom_left = left_sorted[1]

    right = points[-2:]
    right_sorted = sorted(right,key=lambda cnt: cnt[0][1])
    top_right = right_sorted[0]
    bottom_right = right_sorted[1]

    return np.float32([top_left,top_right,bottom_right,bottom_left])


blured = cv2.GaussianBlur(img,(3,3),0)
canny = cv2.Canny(img, 50, 150)  
contours, hierarchy = cv2.findContours(canny, cv2.RETR_EXTERNAL, cv2.CHAIN_APPROX_SIMPLE)

cnt = sorted(contours,key=cv2.contourArea)[-1]

epsilon = 0.1*cv2.arcLength(cnt,True)
approx = cv2.approxPolyDP(cnt,epsilon,True)

newImgSize = np.float32([[0,0],[840,0],[840,594],[0,594]])
M = cv2.getPerspectiveTransform(sort_cw(approx),newImgSize)
processImage = cv2.warpPerspective(img,M,(840,594))

cv2.imwrite('out.jpg',processImage)

def showImage(showImg = img):
    cv2.imshow('img', img)
    cv2.waitKey(0)
    cv2.destroyAllWindows()

def drawPoint(img, x, y):
    point = x, y
    cv2.circle(img, point, 2, (0,255,0),3)