Thinking more...

實際上是用 GDK+GtkDrawingArea 來畫，所以在下面的程式片斷，你會看到我宣告了 GtkDrawingArea 並且實作了 GtkDrawingArea 的 expose 事件。
GDK 支援的圖片格式很多，常見的 jpg、png、bmp 都沒問題。

static gboolean expose_event( GtkWidget* widget, GdkEventExpose* event, gpointer data )
{
 GError* error=NULL;
 int width=widget->allocation.width, height=widget->allocation.height;

 GdkPixbuf* buf=gdk_pixbuf_new_from_file_at_scale( "your_photo.jpg", &error );
 if( buf==NULL )
  g_print("load fail.\n" );
 else
 {
  bufWidth = gdk_pixbuf_get_width( buf );
  bufHeight = gdk_pixbuf_get_height( buf );
  gdk_draw_pixbuf( widget->window, NULL, buf, 0, 0, 0, 0, 
    (width>bufWidth?bufWidth:width), (height>bufHeight?bufHeight:height), 
    GDK_RGB_DITHER_NORMAL, 0, 0 );
  g_object_unref( buf );
 }
}

int main( int argc, char* argv[])
{
 GtkWidget* drawing_area=NULL;

 // 省略一萬行
 g_signal_connect( G_OBJECT(drawing_area), "expose_event", G_CALLBACK( expose_event ), NULL );

 // 再省略兩萬行... 
}