Using OpenCV in GTK sample program "Inverting an image on Image Processing"

In this article I want to show you How we can use the OpenCV on GTK (GIMP toolkit) on fedora.Although GTK+ is a GNU project like the GMP, it is released under the terms of the more liberal LGPL(lesser general public license) that permits software (including closed source proprietary software) to be written using GTK+ without payment of fees, royalties, or other restirictions. The freedom offered by the GTK+ license is in contrast to its competitor QT(you must instead purchase a commercial Qt license in that case).
This program is compile using gcc compiler on fedora. At first you need to install the gtk and gnome on your machine.
In fedra that use RPM packages, you should have at least install the following RPM package.
$  su

$  yum install gtk2
$  yum install gtk2-devel
$  yum install gtk2-engines
$  yum install libgnome-
$  yum install libgnome-devel
$  yum install libgnomeui
$  yum install libgnomeui-devel

Now its time to install OpenCV package.

$ su

$  yum install opencv
$  yum install opencv-devel
All necessary library has been installed. Now you can create program to use OpenCV with GTK.In this program colour of the image is inverted to show how OpenCV can be used in GTK.

//inverting.c

#include <gtk/gtk.h>
#include <glib.h>
#include <opencv/cv.h>
#include <opencv/cxcore.h>

#include <stdio.h>

gint t = 0;
IplImage* opencvImage;
GdkPixbuf* pix;

gboolean
expose_event_callback(GtkWidget *widget, GdkEventExpose *event, gpointer data)
{

  pix = gdk_pixbuf_new_from_data((guchar*) opencvImage->imageData,
      GDK_COLORSPACE_RGB, FALSE, opencvImage->depth, opencvImage->width,
      opencvImage->height, (opencvImage->widthStep), NULL, NULL);

  gdk_draw_pixbuf(widget->window,
      widget->style->fg_gc[GTK_WIDGET_STATE (widget)], pix, 0, 0, 0, 0,
      opencvImage->width, opencvImage->height, GDK_RGB_DITHER_NONE, 0, 0); /* Other possible values are  GDK_RGB_DITHER_MAX,  GDK_RGB_DITHER_NORMAL */

  return TRUE;
}

int
main(int argc, char *argv[])
{
    int height,width,step,channels;
  uchar *data;
  int i,j,k;

  GtkWidget *window;
  GtkWidget *drawing_area;
  gtk_init (&argc, &argv);

//Change this path in order to load any other image.
  opencvImage = cvLoadImage("recharge.JPG", 1);


  // get the image data
  height    = opencvImage->height;
  width     = opencvImage->width;
  step      = opencvImage->widthStep;
  channels  = opencvImage->nChannels;
  data      = (uchar *)opencvImage->imageData;

  // invert the image
  for(i=0;i<height;i++) for(j=0;j<width;j++) for(k=0;k<channels;k++)
    data[i*step+j*channels+k]=255-data[i*step+j*channels+k];


  cvCvtColor(opencvImage, opencvImage, CV_BGR2RGB);

  window = gtk_window_new(GTK_WINDOW_TOPLEVEL);

  gtk_window_set_title(GTK_WINDOW (window), "RESET DEMO");
  g_signal_connect (G_OBJECT (window), "destroy",
      G_CALLBACK (gtk_main_quit), NULL);

  /* Now add a child widget to the aspect frame */
  drawing_area = gtk_drawing_area_new();

  /* Ask for a 200x200 window, but the AspectFrame will give us a 200x100
   * window since we are forcing a 2x1 aspect ratio */
  gtk_widget_set_size_request(drawing_area, opencvImage->width, opencvImage->height);
  gtk_container_add(GTK_CONTAINER (window), drawing_area);
  gtk_widget_show(drawing_area);

  g_signal_connect (G_OBJECT (drawing_area), "expose_event",
      G_CALLBACK (expose_event_callback), NULL);

  gtk_widget_show(window);
  gtk_main();
  return 0;
}

You can compile this program by linking opencv library .