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#!/usr/bin/env python
'''
Feature homography
==================
Example of using features2d framework for interactive video homography matching.
ORB features and FLANN matcher are used. The actual tracking is implemented by
PlaneTracker class in plane_tracker.py
'''
# Python 2/3 compatibility
from __future__ import print_function
import numpy as np
import cv2
import sys
PY3 = sys.version_info[0] == 3
if PY3:
xrange = range
# local modules
from tst_scene_render import TestSceneRender
def intersectionRate(s1, s2):
x1, y1, x2, y2 = s1
s1 = np.array([[x1, y1], [x2,y1], [x2, y2], [x1, y2]])
area, intersection = cv2.intersectConvexConvex(s1, np.array(s2))
return 2 * area / (cv2.contourArea(s1) + cv2.contourArea(np.array(s2)))
from tests_common import NewOpenCVTests
class feature_homography_test(NewOpenCVTests):
render = None
tracker = None
framesCounter = 0
frame = None
def test_feature_homography(self):
self.render = TestSceneRender(self.get_sample('samples/data/graf1.png'),
self.get_sample('samples/data/box.png'), noise = 0.5, speed = 0.5)
self.frame = self.render.getNextFrame()
self.tracker = PlaneTracker()
self.tracker.clear()
self.tracker.add_target(self.frame, self.render.getCurrentRect())
while self.framesCounter < 100:
self.framesCounter += 1
tracked = self.tracker.track(self.frame)
if len(tracked) > 0:
tracked = tracked[0]
self.assertGreater(intersectionRate(self.render.getCurrentRect(), np.int32(tracked.quad)), 0.6)
else:
self.assertEqual(0, 1, 'Tracking error')
self.frame = self.render.getNextFrame()
# built-in modules
from collections import namedtuple
FLANN_INDEX_KDTREE = 1
FLANN_INDEX_LSH = 6
flann_params= dict(algorithm = FLANN_INDEX_LSH,
table_number = 6, # 12
key_size = 12, # 20
multi_probe_level = 1) #2
MIN_MATCH_COUNT = 10
'''
image - image to track
rect - tracked rectangle (x1, y1, x2, y2)
keypoints - keypoints detected inside rect
descrs - their descriptors
data - some user-provided data
'''
PlanarTarget = namedtuple('PlaneTarget', 'image, rect, keypoints, descrs, data')
'''
target - reference to PlanarTarget
p0 - matched points coords in target image
p1 - matched points coords in input frame
H - homography matrix from p0 to p1
quad - target bounary quad in input frame
'''
TrackedTarget = namedtuple('TrackedTarget', 'target, p0, p1, H, quad')
class PlaneTracker:
def __init__(self):
self.detector = cv2.AKAZE_create(threshold = 0.003)
self.matcher = cv2.FlannBasedMatcher(flann_params, {}) # bug : need to pass empty dict (#1329)
self.targets = []
self.frame_points = []
def add_target(self, image, rect, data=None):
'''Add a new tracking target.'''
x0, y0, x1, y1 = rect
raw_points, raw_descrs = self.detect_features(image)
points, descs = [], []
for kp, desc in zip(raw_points, raw_descrs):
x, y = kp.pt
if x0 <= x <= x1 and y0 <= y <= y1:
points.append(kp)
descs.append(desc)
descs = np.uint8(descs)
self.matcher.add([descs])
target = PlanarTarget(image = image, rect=rect, keypoints = points, descrs=descs, data=data)
self.targets.append(target)
def clear(self):
'''Remove all targets'''
self.targets = []
self.matcher.clear()
def track(self, frame):
'''Returns a list of detected TrackedTarget objects'''
self.frame_points, frame_descrs = self.detect_features(frame)
if len(self.frame_points) < MIN_MATCH_COUNT:
return []
matches = self.matcher.knnMatch(frame_descrs, k = 2)
matches = [m[0] for m in matches if len(m) == 2 and m[0].distance < m[1].distance * 0.75]
if len(matches) < MIN_MATCH_COUNT:
return []
matches_by_id = [[] for _ in xrange(len(self.targets))]
for m in matches:
matches_by_id[m.imgIdx].append(m)
tracked = []
for imgIdx, matches in enumerate(matches_by_id):
if len(matches) < MIN_MATCH_COUNT:
continue
target = self.targets[imgIdx]
p0 = [target.keypoints[m.trainIdx].pt for m in matches]
p1 = [self.frame_points[m.queryIdx].pt for m in matches]
p0, p1 = np.float32((p0, p1))
H, status = cv2.findHomography(p0, p1, cv2.RANSAC, 3.0)
status = status.ravel() != 0
if status.sum() < MIN_MATCH_COUNT:
continue
p0, p1 = p0[status], p1[status]
x0, y0, x1, y1 = target.rect
quad = np.float32([[x0, y0], [x1, y0], [x1, y1], [x0, y1]])
quad = cv2.perspectiveTransform(quad.reshape(1, -1, 2), H).reshape(-1, 2)
track = TrackedTarget(target=target, p0=p0, p1=p1, H=H, quad=quad)
tracked.append(track)
tracked.sort(key = lambda t: len(t.p0), reverse=True)
return tracked
def detect_features(self, frame):
'''detect_features(self, frame) -> keypoints, descrs'''
keypoints, descrs = self.detector.detectAndCompute(frame, None)
if descrs is None: # detectAndCompute returns descs=None if no keypoints found
descrs = []
return keypoints, descrs
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