For example, the following code compares the results of the the same operation using pytorch and scipy. The results are not the same.
x = torch.eye(10).view(1, 1, 10, 10)
theta = torch.zeros(1, 2, 3)
angle = np.pi/2.
theta[:, :, :2] = torch.tensor([[np.cos(angle), -1.0*np.sin(angle)],
[np.sin(angle), np.cos(angle)]])
theta[:, :, 2] = 0.5
grid = F.affine_grid(theta, x.size())
x_trans = F.grid_sample(x, grid)
plt.imshow(x.squeeze().numpy())
plt.figure()
plt.imshow(x_trans.squeeze().numpy())
x = np.eye(10)
theta = np.zeros([2, 3])
angle = np.pi/2.
theta = np.float32([[np.cos(angle),-1.0*np.sin(angle),5],[np.sin(angle),np.cos(angle),5]]) # or 7.5 instead of 5
x_trans = scipy.ndimage.affine_transform(x, theta, order=1)
plt.figure()
plt.imshow(x)
plt.figure()
plt.imshow(x_trans)
plt.show()