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| 1 | +#!/usr/bin/env python |
| 2 | + |
| 3 | +''' |
| 4 | +Affine invariant feature-based image matching sample. |
| 5 | +
|
| 6 | +This sample is similar to find_obj.py, but uses the affine transformation |
| 7 | +space sampling technique, called ASIFT [1]. While the original implementation |
| 8 | +is based on SIFT, you can try to use SURF or ORB detectors instead. Homography RANSAC |
| 9 | +is used to reject outliers. Threading is used for faster affine sampling. |
| 10 | +
|
| 11 | +[1] http://www.ipol.im/pub/algo/my_affine_sift/ |
| 12 | +
|
| 13 | +USAGE |
| 14 | + asift.py [--feature=<sift|surf|orb|brisk>[-flann]] [ <image1> <image2> ] |
| 15 | +
|
| 16 | + --feature - Feature to use. Can be sift, surf, orb or brisk. Append '-flann' |
| 17 | + to feature name to use Flann-based matcher instead bruteforce. |
| 18 | +
|
| 19 | + Press left mouse button on a feature point to see its matching point. |
| 20 | +''' |
| 21 | + |
| 22 | +# Python 2/3 compatibility |
| 23 | +from __future__ import print_function |
| 24 | + |
| 25 | +import numpy as np |
| 26 | +import cv2 |
| 27 | + |
| 28 | +# built-in modules |
| 29 | +import itertools as it |
| 30 | +from multiprocessing.pool import ThreadPool |
| 31 | + |
| 32 | +# local modules |
| 33 | +from common import Timer |
| 34 | +from find_obj import init_feature, filter_matches, explore_match |
| 35 | + |
| 36 | + |
| 37 | +def affine_skew(tilt, phi, img, mask=None): |
| 38 | + ''' |
| 39 | + affine_skew(tilt, phi, img, mask=None) -> skew_img, skew_mask, Ai |
| 40 | +
|
| 41 | + Ai - is an affine transform matrix from skew_img to img |
| 42 | + ''' |
| 43 | + h, w = img.shape[:2] |
| 44 | + if mask is None: |
| 45 | + mask = np.zeros((h, w), np.uint8) |
| 46 | + mask[:] = 255 |
| 47 | + A = np.float32([[1, 0, 0], [0, 1, 0]]) |
| 48 | + if phi != 0.0: |
| 49 | + phi = np.deg2rad(phi) |
| 50 | + s, c = np.sin(phi), np.cos(phi) |
| 51 | + A = np.float32([[c,-s], [ s, c]]) |
| 52 | + corners = [[0, 0], [w, 0], [w, h], [0, h]] |
| 53 | + tcorners = np.int32( np.dot(corners, A.T) ) |
| 54 | + x, y, w, h = cv2.boundingRect(tcorners.reshape(1,-1,2)) |
| 55 | + A = np.hstack([A, [[-x], [-y]]]) |
| 56 | + img = cv2.warpAffine(img, A, (w, h), flags=cv2.INTER_LINEAR, borderMode=cv2.BORDER_REPLICATE) |
| 57 | + if tilt != 1.0: |
| 58 | + s = 0.8*np.sqrt(tilt*tilt-1) |
| 59 | + img = cv2.GaussianBlur(img, (0, 0), sigmaX=s, sigmaY=0.01) |
| 60 | + img = cv2.resize(img, (0, 0), fx=1.0/tilt, fy=1.0, interpolation=cv2.INTER_NEAREST) |
| 61 | + A[0] /= tilt |
| 62 | + if phi != 0.0 or tilt != 1.0: |
| 63 | + h, w = img.shape[:2] |
| 64 | + mask = cv2.warpAffine(mask, A, (w, h), flags=cv2.INTER_NEAREST) |
| 65 | + Ai = cv2.invertAffineTransform(A) |
| 66 | + return img, mask, Ai |
| 67 | + |
| 68 | + |
| 69 | +def affine_detect(detector, img, mask=None, pool=None): |
| 70 | + ''' |
| 71 | + affine_detect(detector, img, mask=None, pool=None) -> keypoints, descrs |
| 72 | +
|
| 73 | + Apply a set of affine transormations to the image, detect keypoints and |
| 74 | + reproject them into initial image coordinates. |
| 75 | + See http://www.ipol.im/pub/algo/my_affine_sift/ for the details. |
| 76 | +
|
| 77 | + ThreadPool object may be passed to speedup the computation. |
| 78 | + ''' |
| 79 | + params = [(1.0, 0.0)] |
| 80 | + for t in 2**(0.5*np.arange(1,6)): |
| 81 | + for phi in np.arange(0, 180, 72.0 / t): |
| 82 | + params.append((t, phi)) |
| 83 | + |
| 84 | + def f(p): |
| 85 | + t, phi = p |
| 86 | + timg, tmask, Ai = affine_skew(t, phi, img) |
| 87 | + keypoints, descrs = detector.detectAndCompute(timg, tmask) |
| 88 | + for kp in keypoints: |
| 89 | + x, y = kp.pt |
| 90 | + kp.pt = tuple( np.dot(Ai, (x, y, 1)) ) |
| 91 | + if descrs is None: |
| 92 | + descrs = [] |
| 93 | + return keypoints, descrs |
| 94 | + |
| 95 | + keypoints, descrs = [], [] |
| 96 | + if pool is None: |
| 97 | + ires = it.imap(f, params) |
| 98 | + else: |
| 99 | + ires = pool.imap(f, params) |
| 100 | + |
| 101 | + for i, (k, d) in enumerate(ires): |
| 102 | + print('affine sampling: %d / %d\r' % (i+1, len(params)), end='') |
| 103 | + keypoints.extend(k) |
| 104 | + descrs.extend(d) |
| 105 | + |
| 106 | + print() |
| 107 | + return keypoints, np.array(descrs) |
| 108 | + |
| 109 | +if __name__ == '__main__': |
| 110 | + print(__doc__) |
| 111 | + |
| 112 | + import sys, getopt |
| 113 | + opts, args = getopt.getopt(sys.argv[1:], '', ['feature=']) |
| 114 | + opts = dict(opts) |
| 115 | + feature_name = opts.get('--feature', 'brisk-flann') |
| 116 | + try: |
| 117 | + fn1, fn2 = args |
| 118 | + except: |
| 119 | + fn1 = '../data/aero1.jpg' |
| 120 | + fn2 = '../data/aero3.jpg' |
| 121 | + |
| 122 | + img1 = cv2.imread(fn1, 0) |
| 123 | + img2 = cv2.imread(fn2, 0) |
| 124 | + detector, matcher = init_feature(feature_name) |
| 125 | + |
| 126 | + if img1 is None: |
| 127 | + print('Failed to load fn1:', fn1) |
| 128 | + sys.exit(1) |
| 129 | + |
| 130 | + if img2 is None: |
| 131 | + print('Failed to load fn2:', fn2) |
| 132 | + sys.exit(1) |
| 133 | + |
| 134 | + if detector is None: |
| 135 | + print('unknown feature:', feature_name) |
| 136 | + sys.exit(1) |
| 137 | + |
| 138 | + print('using', feature_name) |
| 139 | + |
| 140 | + pool=ThreadPool(processes = cv2.getNumberOfCPUs()) |
| 141 | + kp1, desc1 = affine_detect(detector, img1, pool=pool) |
| 142 | + kp2, desc2 = affine_detect(detector, img2, pool=pool) |
| 143 | + print('img1 - %d features, img2 - %d features' % (len(kp1), len(kp2))) |
| 144 | + |
| 145 | + def match_and_draw(win): |
| 146 | + with Timer('matching'): |
| 147 | + raw_matches = matcher.knnMatch(desc1, trainDescriptors = desc2, k = 2) #2 |
| 148 | + p1, p2, kp_pairs = filter_matches(kp1, kp2, raw_matches) |
| 149 | + if len(p1) >= 4: |
| 150 | + H, status = cv2.findHomography(p1, p2, cv2.RANSAC, 5.0) |
| 151 | + print('%d / %d inliers/matched' % (np.sum(status), len(status))) |
| 152 | + # do not draw outliers (there will be a lot of them) |
| 153 | + kp_pairs = [kpp for kpp, flag in zip(kp_pairs, status) if flag] |
| 154 | + else: |
| 155 | + H, status = None, None |
| 156 | + print('%d matches found, not enough for homography estimation' % len(p1)) |
| 157 | + |
| 158 | + vis = explore_match(win, img1, img2, kp_pairs, None, H) |
| 159 | + |
| 160 | + |
| 161 | + match_and_draw('affine find_obj') |
| 162 | + cv2.waitKey() |
| 163 | + cv2.destroyAllWindows() |
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