image rotation function

rotation.py

import numpy as np
from imageio import imsave, imread
import matplotlib.pyplot as plt
import math
from numpy.linalg import inv

img_name = 'xxx.jpg'
img = imread(img_name)
h, w, c = np.shape(img)

def inverse_rotation(img, alpha):
    inv_affine_matrix = inv(np.array([[math.cos(alpha), math.sin(alpha), 0],
                     [-math.sin(alpha), math.cos(alpha), 0],
                     [0, 0, 1]]))
    new_img = np.zeros_like(img)
    for c_idx in range(c):
        for ny_idx in range(h):
            for nx_idx in range(w):
                v = np.matmul(np.array([ny_idx, nx_idx, 1]), inv_affine_matrix)
                y_idx = v[0]
                x_idx = v[1]
                new_img[ny_idx, nx_idx, c_idx] = img[int(y_idx)%h, int(x_idx)%w, c_idx]
    return new_img
  
n_img = inverse_rotation(img, alpha=-math.pi/4)
plt.imshow(n_img)
plt.show()