Add read_frame_as_jpeg example

examples/read_frame_as_jpeg.py

@@ -0,0 +1,28 @@
+#!/usr/bin/env python
+from __future__ import unicode_literals
+import argparse
+import ffmpeg
+import sys
+
+
+parser = argparse.ArgumentParser(
+    description='Read individual video frame into memory as jpeg and write to stdout')
+parser.add_argument('in_filename', help='Input filename')
+parser.add_argument('frame_num', help='Frame number')
+
+
+def read_frame_as_jpeg(in_filename, frame_num):
+    out, err = (
+        ffmpeg
+        .input(in_filename)
+        .filter_('select', 'gte(n,{})'.format(frame_num))
+        .output('pipe:', vframes=1, format='image2', vcodec='mjpeg')
+        .run(capture_stdout=True)
+    )
+    return out
+
+
+if __name__ == '__main__':
+    args = parser.parse_args()
+    out = read_frame_as_jpeg(args.in_filename, args.frame_num)
+    sys.stdout.buffer.write(out)