Play video from file tutorial

.gitignore

@@ -0,0 +1 @@
+opencv/data

opencv/README.md

@@ -9,3 +9,8 @@ Sources:
 * [Getting Started with Videos][Getting Started with Videos].
 
 [Getting Started with Videos]: http://opencv-python-tutroals.readthedocs.io/en/latest/py_tutorials/py_gui/py_video_display/py_video_display.html
+
+## Examples
+
+* capture-video-gray.py: Capture video and apply gray filter.
+* play-video.py: Read video from file.

opencv/play-video.py

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+#!/usr/bin/env python
+
+import numpy as np
+import cv2
+import os
+import tempfile
+from subprocess import call
+
+def screenshot(img):
+    dirname = tempfile._get_default_tempdir()
+    filename = next(tempfile._get_candidate_names()) + '.png'
+    filename = dirname + '/' + filename
+    print('Screenshot %s' % filename)
+    cv2.imwrite(filename, img)
+
+def download(url, path):
+    print("Downloading video: %s" % url)
+    if not os.path.exists(os.path.dirname(video)):
+        os.mkdir(os.path.dirname(video))
+    call(["youtube-dl", url, "-o", video])
+    print("Video saved: %s" % video)
+
+video = 'data/spain-vs-germany-2008.mp4'
+if not os.path.exists(video):
+    url = "https://www.youtube.com/watch?v=qRLbzpy1y8Y"
+    download(url, video)
+cap = cv2.VideoCapture(video)
+
+while (True):
+    # Capture frame-by-frame.
+    success, frame = cap.read()
+
+    # Our operations on the frame come here. 
+    frame = cv2.resize(frame, (640, 480))
+
+    # Display the resulting frame.
+    cv2.imshow('frame', frame)
+
+    # Actions.
+    key = cv2.waitKey(1) & 0xFF
+    if key == ord('q'):
+        break
+    elif key == ord('s'):
+        screenshot(frame)
+
+# When everything done, release the capture.
+cap.release()
+cv2.destroyAllWindows()