fitline.py sample added

samples/python2/fitline.py

+'''
+Robust line fitting.
+==================
+
+Example of using cv2.fitLine function for fitting line to points in presence of outliers.
+
+Usage
+-----
+fitline.py
+
+Switch through different M-estimator functions and see, how well the robust functions
+fit the line even in case of ~50% of outliers.
+
+Keys
+----
+SPACE - generaty random points
+f     - change distance function
+ESC   - exit
+'''
+
+import numpy as np
+import cv2
+import itertools as it
+from common import draw_str
+
+
+w, h = 512, 256
+
+def toint(p):
+    return tuple(map(int, p))
+
+def sample_line(p1, p2, n, noise=0.0):
+    p1 = np.float32(p1)
+    t = np.random.rand(n,1)
+    return p1 + (p2-p1)*t + np.random.normal(size=(n, 2))*noise
+
+dist_func_names = it.cycle('CV_DIST_L2 CV_DIST_L1 CV_DIST_L12 CV_DIST_FAIR CV_DIST_WELSCH CV_DIST_HUBER'.split())
+cur_func_name = dist_func_names.next()
+
+def update(_=None):
+    noise = cv2.getTrackbarPos('noise', 'fit line')
+    n = cv2.getTrackbarPos('point n', 'fit line')
+    r = cv2.getTrackbarPos('outlier %', 'fit line') / 100.0
+    outn = int(n*r)
+
+    p0, p1 = (90, 80), (w-90, h-80)
+    img = np.zeros((h, w, 3), np.uint8)
+    cv2.line(img, toint(p0), toint(p1), (0, 255, 0))
+
+    if n > 0:
+        line_points = sample_line(p0, p1, n-outn, noise)
+        outliers = np.random.rand(outn, 2) * (w, h)
+        points = np.vstack([line_points, outliers])
+        for p in line_points:
+            cv2.circle(img, toint(p), 2, (255, 255, 255), -1)
+        for p in outliers:
+            cv2.circle(img, toint(p), 2, (64, 64, 255), -1)
+        func = getattr(cv2.cv, cur_func_name)
+        vx, vy, cx, cy = cv2.fitLine(np.float32(points), func, 0, 0.01, 0.01)
+        cv2.line(img, (int(cx-vx*w), int(cy-vy*w)), (int(cx+vx*w), int(cy+vy*w)), (0, 0, 255))
+
+    draw_str(img, (20, 20), cur_func_name)
+    cv2.imshow('fit line', img)
+
+if __name__ == '__main__':
+    cv2.namedWindow('fit line')
+    cv2.createTrackbar('noise', 'fit line', 3, 50, update)
+    cv2.createTrackbar('point n', 'fit line', 100, 500, update)
+    cv2.createTrackbar('outlier %', 'fit line', 30, 100, update)
+    while True:
+        update()
+        ch = cv2.waitKey(0)
+        if ch == ord('f'):
+            cur_func_name = dist_func_names.next()
+        if ch == 27:
+            break