opencv/modules/python/test/test_texture_flow.py

#!/usr/bin/env python

'''
Texture flow direction estimation.

Sample shows how cv2.cornerEigenValsAndVecs function can be used
to estimate image texture flow direction.
'''

# Python 2/3 compatibility
from __future__ import print_function

import numpy as np
import cv2
import sys

from tests_common import NewOpenCVTests


class texture_flow_test(NewOpenCVTests):

    def test_texture_flow(self):

        fn = '../../../samples/data/pic6.png'
        img = cv2.imread(fn)

        gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)
        h, w = img.shape[:2]

        eigen = cv2.cornerEigenValsAndVecs(gray, 15, 3)
        eigen = eigen.reshape(h, w, 3, 2)  # [[e1, e2], v1, v2]
        flow = eigen[:,:,2]

        vis = img.copy()
        vis[:] = (192 + np.uint32(vis)) / 2
        d = 80
        points =  np.dstack( np.mgrid[d/2:w:d, d/2:h:d] ).reshape(-1, 2)

        textureVectors = []
        
        for x, y in np.int32(points):
            textureVectors.append(np.int32(flow[y, x]*d))

        eps = 0.05

        testTextureVectors = [[0, 0], [0, 0], [0, 0], [0, 0], [0, 0], 
        [-38, 70], [-79, 3], [0, 0], [0, 0], [-39, 69], [-79, -1],
        [0, 0], [0, 0], [0, -79], [17, -78], [-48, -63], [65, -46],
        [-69, -39], [-48, -63], [-45, 66]]

        for i in range(len(textureVectors)):
            self.assertLessEqual(cv2.norm(textureVectors[i] - testTextureVectors[i], cv2.NORM_L2), eps)