correct_photo_perspective.py

"""
simple tool for performing perspective correction
useful for "flattening" internet photos of things that i want to print or cut
"""
import os
import cv2
import numpy as np


def correct_image(fin, fout, pin, pout, dim=None, show=True):
    """
    correct_image(fin, fout, pin, pout, dim, show)
    fin: input filename
    fout: output filename
    pin: Nx2 array of input points
    pout: Nx2 array of output points
    dim: dimensions of output image (computed if omitted)
    """
    # http://www.learnopencv.com/homography-examples-using-opencv-python-c/

    if dim is None:
        dim = tuple(np.max(pout, axis=0).astype(int))

    im_src = cv2.imread(fin)
    h, status = cv2.findHomography(pin, pout)
    im_dst = cv2.warpPerspective(im_src, h, dim)
    cv2.imwrite(fout, im_dst)

    if show:
        cv2.imshow("Source Image", im_src)
        cv2.imshow("Warped Image", im_dst)
        cv2.waitKey(0)


def correct_ambigram():
    fin = 'original.jpg'
    fout = 'transformed.jpg'
    
    # manually chosen keypoints (source)
    pts_src = np.array([[95.0, 322], [366, 198], [315, 7], [11, 114]])

    # rectified keypoints (destination)
    W, H = 8, 5
    scale = 200
    pts_dst = np.array([[0., H], [W, H], [W, 0], [0, 0]]) * scale

    correct_image(fin, fout, pts_src, pts_dst)