python/gst-test-perspective.py

   1 #!/usr/bin/env python
   2
   3 # test program for the "perspective" geometric tranform element
   4
   5 import cv2
   6 import numpy as np
   7
   8 import gi
   9 gi.require_version('Gst', '1.0')
  10 from gi.repository import Gst
  11 Gst.init(None)
  12
  13 from gi.repository import GObject
  14 GObject.threads_init()
  15
  16
  17 def calc_matrix():
  18     top_x_shift = 200
  19
  20     width, height = 800, 480
  21     corners = np.array([(0, 0), (width, 0), (width, height), (0, height)], dtype=np.float32)
  22     target = np.array([(top_x_shift, 0), (width - top_x_shift, 0), (width, height), (0, height)], dtype=np.float32)
  23
  24     mat = cv2.getPerspectiveTransform(corners, target)
  25     ret, inv_mat = cv2.invert(mat)
  26
  27     return inv_mat.flatten()
  28
  29
  30
  31 def main():
  32     pipeline = Gst.ElementFactory.make('pipeline', None)
  33
  34     videosrc = Gst.ElementFactory.make('videotestsrc', None)
  35     pipeline.add(videosrc)
  36
  37     # Test the perspective element
  38     perspective = Gst.ElementFactory.make("perspective", None)
  39     pipeline.add(perspective)
  40
  41     print perspective.get_property("matrix")
  42
  43     M = calc_matrix()
  44     perspective.set_property("matrix", M)
  45     print perspective.get_property("matrix")
  46
  47     # This should fail!
  48     perspective.set_property("matrix", [0])
  49     print perspective.get_property("matrix")
  50
  51     videoconvert = Gst.ElementFactory.make("autovideoconvert", None)
  52     pipeline.add(videoconvert)
  53
  54     videosink = Gst.ElementFactory.make("autovideosink", None)
  55     pipeline.add(videosink)
  56
  57     caps = Gst.caps_from_string(
  58         "video/x-raw,format=\"AYUV\",width=800,height=480")
  59
  60     videosrc.link_filtered(perspective, caps)
  61     perspective.link(videoconvert)
  62     videoconvert.link(videosink)
  63
  64     pipeline.set_state(Gst.State.PLAYING)
  65
  66     loop = GObject.MainLoop()
  67     loop.run()
  68
  69
  70 if __name__ == '__main__':
  71     main()