deskew.py

import cv2
import numpy as np

def preprocess(image):
    gray = cv2.cvtColor(image, cv2.COLOR_BGR2GRAY)
    gray = cv2.bitwise_not(gray)
    thresh = cv2.threshold(gray, 0, 255,
        cv2.THRESH_BINARY | cv2.THRESH_OTSU)[1]
        
    return thresh

def deskew(image, src):
    coords = np.column_stack(np.where(image > 0))
    angle = cv2.minAreaRect(coords)[-1]
    if angle < -45:
        angle = -(90 + angle)
    else:
        angle = -angle
    (h, w) = image.shape[:2]
    center = (w // 2, h // 2)
    M = cv2.getRotationMatrix2D(center, angle, 1.0)
    rotated = cv2.warpAffine(src, M, (w, h), flags=cv2.INTER_CUBIC, borderMode=cv2.BORDER_REPLICATE)

    return rotated

if __name__ == '__main__':
    frame = cv2.imread("receipt.jpg")
    preproceesed = preprocess(frame)
    corrected = deskew(preproceesed, frame)
    cv2.imshow("Original", frame)
    cv2.imshow("Deskewed", corrected)
    cv2.waitKey(0)