transform.py

import numpy as np
import cv2
from skimage.filters import threshold_local

def make_document(org_img, hull, ratio = 1):
    warped = four_point_transform(org_img, hull[0].reshape(4, 2) * ratio)
    warped = cv2.cvtColor(warped, cv2.COLOR_BGR2GRAY)
    T = threshold_local(warped, 11, offset = 5, method = "gaussian")
    warped = (warped > T).astype("uint8") * 255

    return warped

def order_points(pts):
	rect = np.zeros((4, 2), dtype = "float32")
	
	s = pts.sum(axis = 1)
	rect[0] = pts[np.argmin(s)]
	rect[2] = pts[np.argmax(s)]
	
	diff = np.diff(pts, axis = 1)
	rect[1] = pts[np.argmin(diff)]
	rect[3] = pts[np.argmax(diff)]
	return rect

def four_point_transform(image, pts):
	rect = order_points(pts)
	(tl, tr, br, bl) = rect
	
	widthA = np.sqrt(((br[0] - bl[0]) ** 2) + ((br[1] - bl[1]) ** 2))
	widthB = np.sqrt(((tr[0] - tl[0]) ** 2) + ((tr[1] - tl[1]) ** 2))
	maxWidth = max(int(widthA), int(widthB))
	
	heightA = np.sqrt(((tr[0] - br[0]) ** 2) + ((tr[1] - br[1]) ** 2))
	heightB = np.sqrt(((tl[0] - bl[0]) ** 2) + ((tl[1] - bl[1]) ** 2))
	maxHeight = max(int(heightA), int(heightB))
	
	dst = np.array([
		[0, 0],
		[maxWidth - 1, 0],
		[maxWidth - 1, maxHeight - 1],
		[0, maxHeight - 1]], dtype = "float32")
	
	M = cv2.getPerspectiveTransform(rect, dst)
	warped = cv2.warpPerspective(image, M, (maxWidth, maxHeight))
	
	return warped