From 499120285f40900c0348d09f5a5d8e96a15f3f4c Mon Sep 17 00:00:00 2001
From: Jens Ahrensfeld <jens@jayfield.org>
Date: Fri, 12 Jul 2024 12:17:03 +0200
Subject: [PATCH] Added ocv_opticalflow.py

---
 ocv_opticalflow.py | 63 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 63 insertions(+)
 create mode 100644 ocv_opticalflow.py

diff --git a/ocv_opticalflow.py b/ocv_opticalflow.py
new file mode 100644
index 0000000..01ef53a
--- /dev/null
+++ b/ocv_opticalflow.py
@@ -0,0 +1,63 @@
+import numpy as np
+import cv2 as cv
+import argparse
+
+parser = argparse.ArgumentParser(description='This sample demonstrates Lucas-Kanade Optical Flow calculation. \
+The example file can be downloaded from: \
+https://www.bogotobogo.com/python/OpenCV_Python/images/mean_shift_tracking/slow_traffic_small.mp4')
+parser.add_argument('--image', type=str, help='path to image file', default='data/production_id 4525346 (1080p).mp4')
+args = parser.parse_args()
+
+cap = cv.VideoCapture(args.image)
+
+# params for ShiTomasi corner detection
+feature_params = dict(maxCorners=100, qualityLevel=0.3, minDistance=7, blockSize=7)
+
+# Parameters for lucas kanade optical flow
+lk_params = dict(winSize=(15, 15), maxLevel=2, criteria=(cv.TERM_CRITERIA_EPS | cv.TERM_CRITERIA_COUNT, 10, 0.03))
+
+# Create some random colors
+color = np.random.randint(0, 255, (100, 3))
+
+# Take first frame and find corners in it
+ret, old_frame = cap.read()
+old_gray = cv.cvtColor(old_frame, cv.COLOR_BGR2GRAY)
+p0 = cv.goodFeaturesToTrack(old_gray, mask=None, **feature_params)
+
+# Create a mask image for drawing purposes
+mask = np.zeros_like(old_frame)
+
+while 1:
+	ret, frame = cap.read()
+	if not ret:
+		print('No frames grabbed!')
+		break
+
+	frame_gray = cv.cvtColor(frame, cv.COLOR_BGR2GRAY)
+
+	# calculate optical flow
+	p1, st, err = cv.calcOpticalFlowPyrLK(old_gray, frame_gray, p0, None, **lk_params)
+
+	# Select good points
+	if p1 is not None:
+		good_new = p1[st == 1]
+		good_old = p0[st == 1]
+
+	# draw the tracks
+	for i, (new, old) in enumerate(zip(good_new, good_old)):
+		a, b = new.ravel()
+		c, d = old.ravel()
+		mask = cv.line(mask, (int(a), int(b)), (int(c), int(d)), color[i].tolist(), 2)
+		frame = cv.circle(frame, (int(a), int(b)), 5, color[i].tolist(), -1)
+	img = cv.add(frame, mask)
+
+	cv.imshow('frame', img)
+	k = cv.waitKey(30) & 0xff
+	if k == 27:
+		break
+
+	# Now update the previous frame and previous points
+	old_gray = frame_gray.copy()
+	p0 = good_new.reshape(-1, 1, 2)
+
+cv.destroyAllWindows()