python/gst-test-perspective.py

   1 #!/usr/bin/env python
   2
   3 # test program for the "perspective" geometric tranform element
   4
   5 import cv
   6
   7 import gi
   8 gi.require_version('Gst', '1.0')
   9 from gi.repository import Gst
  10 Gst.init(None)
  11
  12 from gi.repository import GObject
  13 GObject.threads_init()
  14
  15
  16 def calc_matrix():
  17     top_x_shift = 200
  18
  19     width, height = 800, 480
  20     corners = [(0, 0), (width, 0), (width, height), (0, height)]
  21     target = [(top_x_shift, 0), (width - top_x_shift, 0), (width, height), (0, height)]
  22
  23     mat = cv.CreateMat(3, 3, cv.CV_64F)
  24     cv.GetPerspectiveTransform(corners, target, mat)
  25
  26     inv_mat = cv.CreateMat(3, 3, cv.CV_64F)
  27     cv.Invert(mat, inv_mat)
  28
  29     matrix = [inv_mat[j, i] for j in range(mat.rows) for i in range(mat.cols)]
  30     return matrix
  31
  32
  33 def main():
  34     pipeline = Gst.ElementFactory.make('pipeline', None)
  35
  36     videosrc = Gst.ElementFactory.make('videotestsrc', None)
  37     pipeline.add(videosrc)
  38
  39     # Test the perspective element
  40     perspective = Gst.ElementFactory.make("perspective", None)
  41     pipeline.add(perspective)
  42
  43     print perspective.get_property("matrix")
  44
  45     M = calc_matrix()
  46     perspective.set_property("matrix", M)
  47     print perspective.get_property("matrix")
  48
  49     # This should fail!
  50     perspective.set_property("matrix", [0])
  51     print perspective.get_property("matrix")
  52
  53     videoconvert = Gst.ElementFactory.make("autovideoconvert", None)
  54     pipeline.add(videoconvert)
  55
  56     videosink = Gst.ElementFactory.make("autovideosink", None)
  57     pipeline.add(videosink)
  58
  59     caps = Gst.caps_from_string(
  60         "video/x-raw,format=\"AYUV\",width=800,height=480")
  61
  62     videosrc.link_filtered(perspective, caps)
  63     perspective.link(videoconvert)
  64     videoconvert.link(videosink)
  65
  66     pipeline.set_state(Gst.State.PLAYING)
  67
  68     loop = GObject.MainLoop()
  69     loop.run()
  70
  71
  72 if __name__ == '__main__':
  73     main()