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#!/usr/bin/env python
""" - Version 1.0 2012-02-11
Based on the OpenCV demo code
Created for the Pi Robot Project:
Copyright (c) 2011 Patrick Goebel. All rights reserved.
Modify by, this version can be used in opencv3.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
GNU General Public License for more details at:
import roslib
import rospy
import cv2
import numpy as np
from good_features import GoodFeatures
class LKTracker(GoodFeatures):
def __init__(self, node_name):
super(LKTracker, self).__init__(node_name)
self.show_text = rospy.get_param("~show_text", True)
self.feature_size = rospy.get_param("~feature_size", 1)
# LK parameters
self.lk_winSize = rospy.get_param("~lk_winSize", (10, 10))
self.lk_maxLevel = rospy.get_param("~lk_maxLevel", 2)
self.lk_criteria = rospy.get_param("~lk_criteria", (cv2.TERM_CRITERIA_EPS | cv2.TERM_CRITERIA_COUNT, 20, 0.01))
self.lk_params = dict( winSize = self.lk_winSize,
maxLevel = self.lk_maxLevel,
criteria = self.lk_criteria)
self.detect_interval = 1
self.keypoints = None
self.detect_box = None
self.track_box = None
self.mask = None
self.grey = None
self.prev_grey = None
def process_image(self, cv_image):
# If we don't yet have a detection box (drawn by the user
# with the mouse), keep waiting
if self.detect_box is None:
return cv_image
# Create a greyscale version of the image
self.grey = cv2.cvtColor(cv_image, cv2.COLOR_BGR2GRAY)
# Equalize the grey histogram to minimize lighting effects
self.grey = cv2.equalizeHist(self.grey)
# If we haven't yet started tracking, set the track box to the
# detect box and extract the keypoints within it
if self.track_box is None or not self.is_rect_nonzero(self.track_box):
self.track_box = self.detect_box
self.keypoints = self.get_keypoints(self.grey, self.track_box)
if self.prev_grey is None:
self.prev_grey = self.grey
# Now that have keypoints, track them to the next frame
# using optical flow
self.track_box = self.track_keypoints(self.grey, self.prev_grey)
# Process any special keyboard commands for this module
if 32 <= self.keystroke and self.keystroke < 128:
cc = chr(self.keystroke).lower()
if cc == 'c':
# Clear the current keypoints
self.keypoints = None
self.track_box = None
self.detect_box = None
self.prev_grey = self.grey
return cv_image
def track_keypoints(self, grey, prev_grey):
# We are tracking points between the previous frame and the
# current frame
img0, img1 = prev_grey, grey
# Reshape the current keypoints into a numpy array required
# by calcOpticalFlowPyrLK()
p0 = np.float32([p for p in self.keypoints]).reshape(-1, 1, 2)
# Calculate the optical flow from the previous frame to the current frame
p1, st, err = cv2.calcOpticalFlowPyrLK(img0, img1, p0, None, **self.lk_params)
# Do the reverse calculation: from the current frame to the previous frame
p0r, st, err = cv2.calcOpticalFlowPyrLK(img1, img0, p1, None, **self.lk_params)
# Compute the distance between corresponding points in the two flows
d = abs(p0-p0r).reshape(-1, 2).max(-1)
# If the distance between pairs of points is < 1 pixel, set
# a value in the "good" array to True, otherwise False
good = d < 1
# Initialize a list to hold new keypoints
new_keypoints = list()
# Cycle through all current and new keypoints and only keep
# those that satisfy the "good" condition above
for (x, y), good_flag in zip(p1.reshape(-1, 2), good):
if not good_flag:
new_keypoints.append((x, y))
# Draw the keypoint on the image, (x, y), self.feature_size, (0, 255, 0, 0), cv2.FILLED, 8, 0)
# Set the global keypoint list to the new list
self.keypoints = new_keypoints
# If we have enough points, find the best fit ellipse around them
if len(self.keypoints) > 6:
keypoints_array = np.float32([p for p in self.keypoints]).reshape(-1, 1, 2)
track_box = cv2.fitEllipse(keypoints_array)
# Otherwise, find the best fitting rectangle
track_box = cv2.boundingRect(keypoints_matrix)
track_box = None
return track_box
if __name__ == '__main__':
node_name = "lk_tracker"
except KeyboardInterrupt:
print "Shutting down LK Tracking node."
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