starting experiment with ORB descriptors

orbnav.py

@@ -0,0 +1,123 @@
+#!/usr/bin/python
+"""
+  Experiments with SURFnav, well replaced by ORB descriptors -> orbnav
+  usage:
+       ./orbnav.py <input dir>
+"""
+import sys
+import math
+import os
+import cv2
+import numpy as np
+
+# http://opencv-python-tutroals.readthedocs.org/en/latest/py_tutorials/py_feature2d/py_surf_intro/py_surf_intro.html
+# note:
+# SURF is good at handling images with blurring and rotation, but not good at handling viewpoint change and illumination change.
+# or maybe use ORB instead:
+# ORB: An efficient alternative to SIFT or SURF in 2011
+# SIFT and SURF are patented and you are supposed to pay them for its use. But ORB is not !
+# http://opencv-python-tutroals.readthedocs.org/en/latest/py_tutorials/py_feature2d/py_orb/py_orb.html
+
+# workaround taken from
+#    http://stackoverflow.com/questions/20259025/module-object-has-no-attribute-drawmatches-opencv-python
+def drawMatches(img1, kp1, img2, kp2, matches):
+    """
+    My own implementation of cv2.drawMatches as OpenCV 2.4.9
+    does not have this function available but it's supported in
+    OpenCV 3.0.0
+
+    This function takes in two images with their associated 
+    keypoints, as well as a list of DMatch data structure (matches) 
+    that contains which keypoints matched in which images.
+
+    An image will be produced where a montage is shown with
+    the first image followed by the second image beside it.
+
+    Keypoints are delineated with circles, while lines are connected
+    between matching keypoints.
+
+    img1,img2 - Grayscale images
+    kp1,kp2 - Detected list of keypoints through any of the OpenCV keypoint 
+              detection algorithms
+    matches - A list of matches of corresponding keypoints through any
+              OpenCV keypoint matching algorithm
+    """
+
+    # Create a new output image that concatenates the two images together
+    # (a.k.a) a montage
+    rows1 = img1.shape[0]
+    cols1 = img1.shape[1]
+    rows2 = img2.shape[0]
+    cols2 = img2.shape[1]
+
+    out = np.zeros((max([rows1,rows2]),cols1+cols2,3), dtype='uint8')
+
+    # Place the first image to the left
+    out[:rows1,:cols1] = np.dstack([img1, img1, img1])
+
+    # Place the next image to the right of it
+    out[:rows2,cols1:] = np.dstack([img2, img2, img2])
+
+    # For each pair of points we have between both images
+    # draw circles, then connect a line between them
+    for mat in matches:
+
+        # Get the matching keypoints for each of the images
+        img1_idx = mat.queryIdx
+        img2_idx = mat.trainIdx
+
+        # x - columns
+        # y - rows
+        (x1,y1) = kp1[img1_idx].pt
+        (x2,y2) = kp2[img2_idx].pt
+
+        # Draw a small circle at both co-ordinates
+        # radius 4
+        # colour blue
+        # thickness = 1
+        cv2.circle(out, (int(x1),int(y1)), 4, (255, 0, 0), 1)   
+        cv2.circle(out, (int(x2)+cols1,int(y2)), 4, (255, 0, 0), 1)
+
+        # Draw a line in between the two points
+        # thickness = 1
+        # colour blue
+        cv2.line(out, (int(x1),int(y1)), (int(x2)+cols1,int(y2)), (255, 0, 0), 1)
+
+
+    # Show the image
+    cv2.imshow('Matched Features', out)
+    cv2.waitKey(0)
+    cv2.destroyWindow('Matched Features')
+
+    # Also return the image if you'd like a copy
+    return out
+
+
+def orbnav( inDir ):
+    result = None
+    orb = cv2.ORB()
+    bf = cv2.BFMatcher(cv2.NORM_HAMMING, crossCheck=True)
+
+    img1, kp1, des1 = None, None, None
+    for name in os.listdir(inDir):
+        print name
+        img2 = cv2.imread( os.path.join(inDir, name) )
+        kp2, des2 = orb.detectAndCompute(img2, None)
+        print len(kp2)
+        if img1 is not None:
+            matches = bf.match(des1,des2)
+            matches = sorted(matches, key = lambda x:x.distance)
+            gray1 = cv2.cvtColor( img1, cv2.COLOR_BGR2GRAY )
+            gray2 = cv2.cvtColor( img2, cv2.COLOR_BGR2GRAY )
+            img3 = drawMatches(gray1,kp1,gray2,kp2,matches[:10])
+            cv2.imwrite( "tmp.jpg", img3 )
+        img1, kp1, des1 = img2, kp2, des2
+
+if __name__ == "__main__":
+    if len(sys.argv) < 2:
+        print __doc__
+        sys.exit(2)
+    orbnav( sys.argv[1] )
+
+# vim: expandtab sw=4 ts=4 
+