"""
===============================================
Local Binary Pattern for texture classification
===============================================

In this example, we will see how to classify textures based on LBP (Local
Binary Pattern). The histogram of the LBP result is a good measure to classify
textures. For simplicity the histogram distributions are then tested against
each other using the Kullback-Leibler-Divergence.
"""

import numpy as np
import matplotlib
import matplotlib.pyplot as plt
from skimage.transform import rotate
import skimage.feature as ft
from skimage import data


# settings for LBP
METHOD = 'uniform'
P = 16
R = 2
matplotlib.rcParams['font.size'] = 9


def kullback_leibler_divergence(p, q):
    p = np.asarray(p)
    q = np.asarray(q)
    filt = np.logical_and(p != 0, q != 0)
    return np.sum(p[filt] * np.log2(p[filt] / q[filt]))


def match(refs, img):
    best_score = 10
    best_name = None
    lbp = ft.local_binary_pattern(img, P, R, METHOD)
    hist, _ = np.histogram(lbp, normed=True, bins=P + 2, range=(0, P + 2))
    for name, ref in refs.items():
        ref_hist, _ = np.histogram(ref, normed=True, bins=P + 2,
                                   range=(0, P + 2))
        score = kullback_leibler_divergence(hist, ref_hist)
        if score < best_score:
            best_score = score
            best_name = name
    return best_name


brick = data.load('brick.png')
grass = data.load('grass.png')
wall = data.load('rough-wall.png')

refs = {
    'brick': ft.local_binary_pattern(brick, P, R, METHOD),
    'grass': ft.local_binary_pattern(grass, P, R, METHOD),
    'wall': ft.local_binary_pattern(wall, P, R, METHOD)
}

# classify rotated textures
print 'Rotated images matched against references using LBP:'
print 'original: brick, rotated: 30deg, match result:',
print match(refs, rotate(brick, angle=30, resize=False))
print 'original: brick, rotated: 70deg, match result:',
print match(refs, rotate(brick, angle=70, resize=False))
print 'original: grass, rotated: 145deg, match result:',
print match(refs, rotate(grass, angle=145, resize=False))

# plot histograms of LBP of textures
fig, ((ax1, ax2, ax3), (ax4, ax5, ax6)) = plt.subplots(nrows=2, ncols=3,
                                                       figsize=(9, 6))
plt.gray()

ax1.imshow(brick)
ax1.axis('off')
ax4.hist(refs['brick'].ravel(), normed=True, bins=P + 2, range=(0, P + 2))
ax4.set_ylabel('Percentage')

ax2.imshow(grass)
ax2.axis('off')
ax5.hist(refs['grass'].ravel(), normed=True, bins=P + 2, range=(0, P + 2))
ax5.set_xlabel('Uniform LBP values')

ax3.imshow(wall)
ax3.axis('off')
ax6.hist(refs['wall'].ravel(), normed=True, bins=P + 2, range=(0, P + 2))

plt.show()