/*
 * GStreamer hand gesture detection plugins
 * Copyright (C) 2012 Andol Li <<andol@andol.info>>
 * Copyright (C) 2013 Sreerenj Balachandran <sreerenj.balachandran@intel.com>
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
 * DEALINGS IN THE SOFTWARE.
 *
 * Alternatively, the contents of this file may be used under the
 * GNU Lesser General Public License Version 2.1 (the "LGPL"), in
 * which case the following provisions apply instead of the ones
 * mentioned above:
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Library General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Library General Public License for more details.
 *
 * You should have received a copy of the GNU Library General Public
 * License along with this library; if not, write to the
 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 * Boston, MA 02111-1307, USA.
 */
/**
 * SECTION:video-filter-handdetect
 *
 * FIXME:operates hand gesture detection in video streams and images,
 * and enable media operation e.g. play/stop/fast forward/back rewind.
 *
 * <refsect2>
 * <title>Example launch line</title>
 * |[
 * gst-launch-1.0 autovideosrc ! videoconvert ! "video/x-raw, format=RGB, width=320, height=240" ! \
 * videoscale ! handdetect ! videoconvert ! xvimagesink
 * ]|
 * </refsect2>
 */

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif

/* element header */
#include "gsthanddetect.h"
#include <opencv2/imgproc.hpp>
#if (CV_MAJOR_VERSION >= 4)
#include <opencv2/imgproc/imgproc_c.h>
#endif

GST_DEBUG_CATEGORY_STATIC (gst_handdetect_debug);
#define GST_CAT_DEFAULT gst_handdetect_debug
#if (CV_MAJOR_VERSION < 4)
#define CASCADE_DO_CANNY_PRUNING CV_HAAR_DO_CANNY_PRUNING
#endif

/* define HAAR files */
#define HAAR_FILE_FIST GST_HAAR_CASCADES_DIR G_DIR_SEPARATOR_S "fist.xml"
#define HAAR_FILE_PALM GST_HAAR_CASCADES_DIR G_DIR_SEPARATOR_S "palm.xml"

using namespace cv;
using namespace std;
/* Filter signals and args */
enum
{
  /* FILL ME */
  LAST_SIGNAL
};

enum
{
  PROP_0,
  PROP_DISPLAY,
  PROP_PROFILE_FIST,
  PROP_PROFILE_PALM,
  PROP_ROI_X,
  PROP_ROI_Y,
  PROP_ROI_WIDTH,
  PROP_ROI_HEIGHT
};

/* the capabilities of the inputs and outputs */
static GstStaticPadTemplate sink_factory = GST_STATIC_PAD_TEMPLATE ("sink",
    GST_PAD_SINK,
    GST_PAD_ALWAYS,
    GST_STATIC_CAPS (GST_VIDEO_CAPS_MAKE ("RGB"))
    );
static GstStaticPadTemplate src_factory = GST_STATIC_PAD_TEMPLATE ("src",
    GST_PAD_SRC,
    GST_PAD_ALWAYS,
    GST_STATIC_CAPS (GST_VIDEO_CAPS_MAKE ("RGB"))
    );

static void gst_handdetect_set_property (GObject * object, guint prop_id,
    const GValue * value, GParamSpec * pspec);
static void gst_handdetect_get_property (GObject * object, guint prop_id,
    GValue * value, GParamSpec * pspec);
static gboolean gst_handdetect_set_caps (GstOpencvVideoFilter * transform,
    gint in_width, gint in_height, gint in_depth, gint in_channels,
    gint out_width, gint out_height, gint out_depth, gint out_channels);
static GstFlowReturn gst_handdetect_transform_ip (GstOpencvVideoFilter *
    transform, GstBuffer * buffer, IplImage * img);

static CascadeClassifier *gst_handdetect_load_profile (GstHanddetect * filter,
    gchar * profile);

static void gst_handdetect_navigation_interface_init (GstNavigationInterface *
    iface);
static void gst_handdetect_navigation_send_event (GstNavigation * navigation,
    GstStructure * structure);

G_DEFINE_TYPE_WITH_CODE (GstHanddetect, gst_handdetect,
    GST_TYPE_OPENCV_VIDEO_FILTER,
    G_IMPLEMENT_INTERFACE (GST_TYPE_NAVIGATION,
        gst_handdetect_navigation_interface_init););

static void
gst_handdetect_navigation_interface_init (GstNavigationInterface * iface)
{
  iface->send_event = gst_handdetect_navigation_send_event;
}

/* FIXME: this function used to parse the region of interests coordinates
 * sending from applications when the hand gestures reach the defined regions of interests,
 * at this moment this function is not doing anything significantly
 * but will be CHANGED when the gstreamer is patched with new hand gesture events
 */
static void
gst_handdetect_navigation_send_event (GstNavigation * navigation,
    GstStructure * structure)
{
  GstHanddetect *filter = GST_HANDDETECT (navigation);
  GstPad *peer;

  if ((peer = gst_pad_get_peer (GST_BASE_TRANSFORM_CAST (filter)->sinkpad))) {
    GstEvent *event;
    event = gst_event_new_navigation (structure);
    gst_pad_send_event (peer, event);
    gst_object_unref (peer);
  }
}

/* clean opencv images and parameters */
static void
gst_handdetect_finalize (GObject * obj)
{
  GstHanddetect *filter = GST_HANDDETECT (obj);

  if (filter->cvGray)
    cvReleaseImage (&filter->cvGray);
  g_free (filter->profile_fist);
  g_free (filter->profile_palm);
  delete (filter->best_r);

  G_OBJECT_CLASS (gst_handdetect_parent_class)->finalize (obj);
}

/* initialise the HANDDETECT class */
static void
gst_handdetect_class_init (GstHanddetectClass * klass)
{
  GObjectClass *gobject_class;
  GstOpencvVideoFilterClass *gstopencvbasefilter_class;

  GstElementClass *element_class = GST_ELEMENT_CLASS (klass);
  gobject_class = (GObjectClass *) klass;
  gstopencvbasefilter_class = (GstOpencvVideoFilterClass *) klass;

  gstopencvbasefilter_class->cv_trans_ip_func = gst_handdetect_transform_ip;
  gstopencvbasefilter_class->cv_set_caps = gst_handdetect_set_caps;

  gobject_class->finalize = GST_DEBUG_FUNCPTR (gst_handdetect_finalize);
  gobject_class->set_property = gst_handdetect_set_property;
  gobject_class->get_property = gst_handdetect_get_property;

  g_object_class_install_property (gobject_class,
      PROP_DISPLAY,
      g_param_spec_boolean ("display",
          "Display",
          "Whether the detected hands are highlighted in output frame",
          TRUE, (GParamFlags) G_PARAM_READWRITE)
      );
  g_object_class_install_property (gobject_class,
      PROP_PROFILE_FIST,
      g_param_spec_string ("profile_fist",
          "Profile_fist",
          "Location of HAAR cascade file (fist gesture)",
          HAAR_FILE_FIST, (GParamFlags) G_PARAM_READWRITE)
      );
  g_object_class_install_property (gobject_class,
      PROP_PROFILE_PALM,
      g_param_spec_string ("profile_palm",
          "Profile_palm",
          "Location of HAAR cascade file (palm gesture)",
          HAAR_FILE_PALM, (GParamFlags) G_PARAM_READWRITE)
      );
  /* FIXME: property name needs fixing */
  g_object_class_install_property (gobject_class,
      PROP_ROI_X,
      g_param_spec_int ("ROI_X",
          "ROI_X",
          "X of left-top pointer in region of interest \nGestures in the defined region of interest will emit messages",
          0, INT_MAX, 0, (GParamFlags) G_PARAM_READWRITE)
      );
  /* FIXME: property name needs fixing */
  g_object_class_install_property (gobject_class,
      PROP_ROI_Y,
      g_param_spec_int ("ROI_Y",
          "ROI_Y",
          "Y of left-top pointer in region of interest \nGestures in the defined region of interest will emit messages",
          0, INT_MAX, 0, (GParamFlags) G_PARAM_READWRITE)
      );
  /* FIXME: property name needs fixing */
  g_object_class_install_property (gobject_class,
      PROP_ROI_WIDTH,
      g_param_spec_int ("ROI_WIDTH",
          "ROI_WIDTH",
          "WIDTH of left-top pointer in region of interest \nGestures in the defined region of interest will emit messages",
          0, INT_MAX, 0, (GParamFlags) G_PARAM_READWRITE)
      );
  /* FIXME: property name needs fixing */
  g_object_class_install_property (gobject_class,
      PROP_ROI_HEIGHT,
      g_param_spec_int ("ROI_HEIGHT",
          "ROI_HEIGHT",
          "HEIGHT of left-top pointer in region of interest \nGestures in the defined region of interest will emit messages",
          0, INT_MAX, 0, (GParamFlags) G_PARAM_READWRITE)
      );

  gst_element_class_set_static_metadata (element_class,
      "handdetect",
      "Filter/Effect/Video",
      "Performs hand gesture detection on videos, providing detected hand positions via bus message and navigation event, and deals with hand gesture events",
      "Andol Li <andol@andol.info>");

  gst_element_class_add_static_pad_template (element_class, &src_factory);
  gst_element_class_add_static_pad_template (element_class, &sink_factory);

}

/* initialise the new element
 * instantiate pads and add them to element
 * set pad call-back functions
 * initialise instance structure
 */
static void
gst_handdetect_init (GstHanddetect * filter)
{
  const gchar *haar_path;

  haar_path = g_getenv ("GST_HAAR_CASCADES_PATH");
  if (haar_path) {
    filter->profile_fist = g_build_filename (haar_path, "fist.xml", NULL);
    filter->profile_palm = g_build_filename (haar_path, "palm.xml", NULL);
  } else {
    filter->profile_fist = g_strdup (HAAR_FILE_FIST);
    filter->profile_palm = g_strdup (HAAR_FILE_PALM);
  }

  filter->roi_x = 0;
  filter->roi_y = 0;
  filter->roi_width = 0;
  filter->roi_height = 0;
  filter->display = TRUE;

  filter->cvCascade_fist =
      gst_handdetect_load_profile (filter, filter->profile_fist);
  filter->cvCascade_palm =
      gst_handdetect_load_profile (filter, filter->profile_palm);

  gst_opencv_video_filter_set_in_place (GST_OPENCV_VIDEO_FILTER_CAST (filter),
      TRUE);
}

static void
gst_handdetect_set_property (GObject * object, guint prop_id,
    const GValue * value, GParamSpec * pspec)
{
  GstHanddetect *filter = GST_HANDDETECT (object);

  switch (prop_id) {
    case PROP_PROFILE_FIST:
      g_free (filter->profile_fist);
      if (filter->cvCascade_fist)
        delete filter->cvCascade_fist;
      filter->profile_fist = g_value_dup_string (value);
      filter->cvCascade_fist =
          gst_handdetect_load_profile (filter, filter->profile_fist);
      break;
    case PROP_PROFILE_PALM:
      g_free (filter->profile_palm);
      if (filter->cvCascade_palm)
        delete filter->cvCascade_palm;
      filter->profile_palm = g_value_dup_string (value);
      filter->cvCascade_palm =
          gst_handdetect_load_profile (filter, filter->profile_palm);
      break;
    case PROP_DISPLAY:
      filter->display = g_value_get_boolean (value);
      break;
    case PROP_ROI_X:
      filter->roi_x = g_value_get_int (value);
      break;
    case PROP_ROI_Y:
      filter->roi_y = g_value_get_int (value);
      break;
    case PROP_ROI_WIDTH:
      filter->roi_width = g_value_get_int (value);
      break;
    case PROP_ROI_HEIGHT:
      filter->roi_height = g_value_get_int (value);
      break;
    default:
      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
      break;
  }
}

static void
gst_handdetect_get_property (GObject * object, guint prop_id, GValue * value,
    GParamSpec * pspec)
{
  GstHanddetect *filter = GST_HANDDETECT (object);

  switch (prop_id) {
    case PROP_DISPLAY:
      g_value_set_boolean (value, filter->display);
      break;
    case PROP_PROFILE_FIST:
      g_value_set_string (value, filter->profile_fist);
      break;
    case PROP_PROFILE_PALM:
      g_value_set_string (value, filter->profile_palm);
      break;
    case PROP_ROI_X:
      g_value_set_int (value, filter->roi_x);
      break;
    case PROP_ROI_Y:
      g_value_set_int (value, filter->roi_y);
      break;
    case PROP_ROI_WIDTH:
      g_value_set_int (value, filter->roi_width);
      break;
    case PROP_ROI_HEIGHT:
      g_value_set_int (value, filter->roi_height);
      break;
    default:
      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
      break;
  }
}

/* GstElement vmethod implementations */
/* this function handles the link with other elements */
static gboolean
gst_handdetect_set_caps (GstOpencvVideoFilter * transform,
    gint in_width, gint in_height, gint in_depth, gint in_channels,
    gint out_width, gint out_height, gint out_depth, gint out_channels)
{
  GstHanddetect *filter;
  filter = GST_HANDDETECT (transform);

  /* 320 x 240 is with the best detect accuracy, if not, give info */
  if (in_width != 320 || in_height != 240)
    GST_WARNING_OBJECT (filter,
        "resize to 320 x 240 to have best detect accuracy.\n");

  if (filter->cvGray)
    cvReleaseImage (&filter->cvGray);
  filter->cvGray =
      cvCreateImage (cvSize (in_width, in_height), IPL_DEPTH_8U, 1);

  return TRUE;
}

/* Hand detection function
 * This function does the actual processing 'of hand detect and display'
 */
static GstFlowReturn
gst_handdetect_transform_ip (GstOpencvVideoFilter * transform,
    GstBuffer * buffer, IplImage * img)
{
  GstHanddetect *filter = GST_HANDDETECT (transform);
  Rect *r;
  GstStructure *s;
  GstMessage *m;
  unsigned int i;
  vector < Rect > hands;

  /* check detection cascades */
  if (filter->cvCascade_fist && filter->cvCascade_palm) {
    /* cvt to gray colour space for hand detect */
    cvCvtColor (img, filter->cvGray, CV_RGB2GRAY);

    /* detect FIST gesture fist */
    Mat image = cvarrToMat (filter->cvGray);
    Mat roi (image, Rect (filter->cvGray->origin,
            filter->cvGray->origin, filter->cvGray->width,
            filter->cvGray->height));
    filter->cvCascade_fist->detectMultiScale (roi, hands, 1.1, 2,
        CASCADE_DO_CANNY_PRUNING, cvSize (24, 24), cvSize (0, 0));

    /* if FIST gesture detected */
    if (!hands.empty ()) {

      int min_distance, distance;
      Rect temp_r;
      CvPoint c;

      /* Go through all detected FIST gestures to get the best one
       * prev_r => previous hand
       * best_r => best hand in this frame
       */
      /* set min_distance for init comparison */
      min_distance = img->width + img->height;
      /* Init filter->prev_r */
      temp_r = Rect (0, 0, 0, 0);
      if (filter->prev_r == NULL)
        filter->prev_r = &temp_r;
      /* Get the best FIST gesture */
      for (i = 0; i < hands.size (); i++) {
        r = &hands[i];
        distance = (int) sqrt (pow ((r->x - filter->prev_r->x),
                2) + pow ((r->y - filter->prev_r->y), 2));
        if (distance <= min_distance) {
          min_distance = distance;
          delete (filter->best_r);
          filter->best_r = new Rect (*r);
        }
      }
      /* Save best_r as prev_r for next frame comparison */
      filter->prev_r = filter->best_r;

      /* send msg to app/bus if the detected gesture falls in the region of interest */
      /* get center point of gesture */
      c = cvPoint (filter->best_r->x + filter->best_r->width / 2,
          filter->best_r->y + filter->best_r->height / 2);
      /* send message:
       * if the center point is in the region of interest, OR,
       * if the region of interest remains default as (0,0,0,0)*/
      if ((c.x >= filter->roi_x && c.x <= (filter->roi_x + filter->roi_width)
              && c.y >= filter->roi_y
              && c.y <= (filter->roi_y + filter->roi_height))
          || (filter->roi_x == 0
              && filter->roi_y == 0
              && filter->roi_width == 0 && filter->roi_height == 0)) {
        /* Define structure for message post */
        s = gst_structure_new ("hand-gesture",
            "gesture", G_TYPE_STRING, "fist",
            "x", G_TYPE_INT,
            (gint) (filter->best_r->x + filter->best_r->width * 0.5), "y",
            G_TYPE_INT,
            (gint) (filter->best_r->y + filter->best_r->height * 0.5), "width",
            G_TYPE_INT, (gint) filter->best_r->width, "height", G_TYPE_INT,
            (gint) filter->best_r->height, NULL);
        /* Init message element */
        m = gst_message_new_element (GST_OBJECT (filter), s);
        /* Send message */
        gst_element_post_message (GST_ELEMENT (filter), m);

#if 0
        /* send event
         * here we use mouse-move event instead of fist-move or palm-move event
         * !!! this will CHANGE in the future !!!
         * !!! by adding gst_navigation_send_hand_detect_event() in navigation.c !!!
         */
        gst_navigation_send_mouse_event (GST_NAVIGATION (filter),
            "mouse-move",
            0,
            (double) (filter->best_r->x + filter->best_r->width * 0.5),
            (double) (filter->best_r->y + filter->best_r->height * 0.5));

#endif
      }
      /* Check filter->display,
       * If TRUE, displaying red circle marker in the out frame */
      if (filter->display) {
        CvPoint center;
        int radius;
        center.x = cvRound ((filter->best_r->x + filter->best_r->width * 0.5));
        center.y = cvRound ((filter->best_r->y + filter->best_r->height * 0.5));
        radius =
            cvRound ((filter->best_r->width + filter->best_r->height) * 0.25);
        cvCircle (img, center, radius, CV_RGB (0, 0, 200), 1, 8, 0);
      }
    } else {
      /* if NO FIST gesture, detecting PALM gesture */
#if (CV_MAJOR_VERSION >= 4)
      filter->cvCascade_palm->detectMultiScale (roi, hands, 1.1, 2,
          CASCADE_DO_CANNY_PRUNING, cvSize (24, 24), cvSize (0, 0));
#else
      filter->cvCascade_palm->detectMultiScale (roi, hands, 1.1, 2,
          CV_HAAR_DO_CANNY_PRUNING, cvSize (24, 24), cvSize (0, 0));
#endif
      /* if PALM detected */
      if (!hands.empty ()) {
        int min_distance, distance;
        Rect temp_r;
        CvPoint c;

        if (filter->display) {
          GST_DEBUG_OBJECT (filter, "%d PALM gestures detected\n",
              (int) hands.size ());
        }
        /* Go through all detected PALM gestures to get the best one
         * prev_r => previous hand
         * best_r => best hand in this frame
         */
        /* suppose a min_distance for init comparison */
        min_distance = img->width + img->height;
        /* Init filter->prev_r */
        temp_r = Rect (0, 0, 0, 0);
        if (filter->prev_r == NULL)
          filter->prev_r = &temp_r;
        /* Get the best PALM gesture */
        for (i = 0; i < hands.size (); ++i) {
          r = &hands[i];
          distance = (int) sqrt (pow ((r->x - filter->prev_r->x),
                  2) + pow ((r->y - filter->prev_r->y), 2));
          if (distance <= min_distance) {
            min_distance = distance;
            delete (filter->best_r);
            filter->best_r = new Rect (*r);
          }
        }
        /* Save best_r as prev_r for next frame comparison */
        filter->prev_r = filter->best_r;

        /* send msg to app/bus if the detected gesture falls in the region of interest */
        /* get center point of gesture */
        c = cvPoint (filter->best_r->x + filter->best_r->width / 2,
            filter->best_r->y + filter->best_r->height / 2);
        /* send message:
         * if the center point is in the region of interest, OR,
         * if the region of interest remains default as (0,0,0,0)*/
        if (((gint) c.x >= filter->roi_x
                && (gint) c.x <= (filter->roi_x + filter->roi_width)
                && (gint) c.y >= filter->roi_y
                && (gint) c.y <= (filter->roi_y + filter->roi_height))
            || (filter->roi_x == 0 && filter->roi_y == 0
                && filter->roi_width == 0 && filter->roi_height == 0)) {
          /* Define structure for message post */
          s = gst_structure_new ("hand-gesture",
              "gesture", G_TYPE_STRING, "palm",
              "x", G_TYPE_INT,
              (gint) (filter->best_r->x + filter->best_r->width * 0.5), "y",
              G_TYPE_INT,
              (gint) (filter->best_r->y + filter->best_r->height * 0.5),
              "width", G_TYPE_INT, (gint) filter->best_r->width, "height",
              G_TYPE_INT, (gint) filter->best_r->height, NULL);
          /* Init message element */
          m = gst_message_new_element (GST_OBJECT (filter), s);
          /* Send message */
          gst_element_post_message (GST_ELEMENT (filter), m);

#if 0
          /* send event
           * here we use mouse-move event instead of fist-move or palm-move event
           * !!! this will CHANGE in the future !!!
           * !!! by adding gst_navigation_send_hand_detect_event() in navigation.c !!!
           */
          gst_navigation_send_mouse_event (GST_NAVIGATION (filter),
              "mouse-move",
              0,
              (double) (filter->best_r->x + filter->best_r->width * 0.5),
              (double) (filter->best_r->y + filter->best_r->height * 0.5));

          /* or use another way to send upstream navigation event for debug
           *
           * GstEvent *event =
           * gst_event_new_navigation (gst_structure_new
           * ("application/x-gst-navigation", "event", G_TYPE_STRING,
           * "mouse-move",
           * "button", G_TYPE_INT, 0,
           * "pointer_x", G_TYPE_DOUBLE,
           * (double) (filter->best_r->x + filter->best_r->width * 0.5),
           * "pointer_y", G_TYPE_DOUBLE,
           * (double) (filter->best_r->y + filter->best_r->height * 0.5),
           * NULL));
           * gst_pad_send_event (GST_BASE_TRANSFORM_CAST (filter)->srcpad, event);
           */
#endif
        }
        /* Check filter->display,
         * If TRUE, displaying red circle marker in the out frame */
        if (filter->display) {
          CvPoint center;
          int radius;
          center.x =
              cvRound ((filter->best_r->x + filter->best_r->width * 0.5));
          center.y =
              cvRound ((filter->best_r->y + filter->best_r->height * 0.5));
          radius =
              cvRound ((filter->best_r->width + filter->best_r->height) * 0.25);
          cvCircle (img, center, radius, CV_RGB (0, 0, 200), 1, 8, 0);
        }
      }
    }
  }

  /* Push out the incoming buffer */
  return GST_FLOW_OK;
}

static CascadeClassifier *
gst_handdetect_load_profile (GstHanddetect * filter, gchar * profile)
{
  CascadeClassifier *cascade;

  cascade = new CascadeClassifier (profile);
  if (cascade->empty ()) {
    GST_ERROR_OBJECT (filter, "Invalid profile file: %s", profile);
    delete cascade;
    return NULL;
  }

  return cascade;
}

/* Entry point to initialize the plug-in
 * Initialize the plug-in itself
 * Register the element factories and other features
 */
gboolean
gst_handdetect_plugin_init (GstPlugin * plugin)
{
  GST_DEBUG_CATEGORY_INIT (gst_handdetect_debug,
      "handdetect", 0, "opencv hand gesture detection");
  return gst_element_register (plugin, "handdetect", GST_RANK_NONE,
      GST_TYPE_HANDDETECT);
}