title: I used Zbar on Raspberry to san qrcode but there are some problems
body: <p>I have installed zbar library and gtk library on Raspberry,but when I compile the example zbargtk.c that provided by the zbar,it can't be compiled.
  The command I used is gcc -o testgtk testgtk.c <code>pkg-config --libs --cflags gtk+-2.0 zbar</code>. </p>
  
  <p>I have spent three days to deal this problem,but I can't solve it.
  Here are the errors i get:</p>
  
  <pre><code>pi@raspberrypi ~/Desktop $ gcc -o testgtk testgtk.c `pkg-config --libs --cflags gtk+-2.0 zbar`
  testgtk.c: In function ‘main’:
  testgtk.c:149:5: warning: ‘g_thread_init’ is deprecated (declared at /usr/include/glib-2.0/glib/deprecated/gthread.h:261) [-Wdeprecated-declarations]
  /tmp/ccF6LqbT.o: In function `video_enabled':
  testgtk.c:(.text+0x12c): undefined reference to `zbar_gtk_get_type'
  testgtk.c:(.text+0x148): undefined reference to `zbar_gtk_get_video_enabled'
  testgtk.c:(.text+0x154): undefined reference to `zbar_gtk_get_video_opened'
  /tmp/ccF6LqbT.o: In function `video_opened':
  testgtk.c:(.text+0x1dc): undefined reference to `zbar_gtk_get_type'
  testgtk.c:(.text+0x1f8): undefined reference to `zbar_gtk_get_video_opened'
  testgtk.c:(.text+0x204): undefined reference to `zbar_gtk_get_video_enabled'
  /tmp/ccF6LqbT.o: In function `video_changed':
  testgtk.c:(.text+0x2b8): undefined reference to `zbar_gtk_get_type'
  testgtk.c:(.text+0x300): undefined reference to `zbar_gtk_set_video_device'
  /tmp/ccF6LqbT.o: In function `status_button_toggled':
  testgtk.c:(.text+0x320): undefined reference to `zbar_gtk_get_type'
  testgtk.c:(.text+0x33c): undefined reference to `zbar_gtk_get_video_opened'
  testgtk.c:(.text+0x348): undefined reference to `zbar_gtk_get_video_enabled'
  testgtk.c:(.text+0x378): undefined reference to `zbar_gtk_get_type'
  testgtk.c:(.text+0x398): undefined reference to `zbar_gtk_set_video_enabled'
  /tmp/ccF6LqbT.o: In function `open_button_clicked':
  testgtk.c:(.text+0x55c): undefined reference to `zbar_gtk_get_type'
  testgtk.c:(.text+0x57c): undefined reference to `zbar_gtk_scan_image'
  /tmp/ccF6LqbT.o: In function `main':
  testgtk.c:(.text+0x620): undefined reference to `g_thread_init'
  testgtk.c:(.text+0x708): undefined reference to `zbar_gtk_new'
  testgtk.c:(.text+0x920): undefined reference to `scan_video'
  collect2: ld returned 1 exit status
  </code></pre>