libextractor

thumbnailgtk_extractor.c (5877B)

---

 /*
      This file is part of libextractor.
      Copyright (C) 2005, 2009, 2012 Vidyut Samanta and Christian Grothoff
 
      libextractor is free software; you can redistribute it and/or modify
      it under the terms of the GNU General Public License as published
      by the Free Software Foundation; either version 3, or (at your
      option) any later version.
 
      libextractor 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
      General Public License for more details.
 
      You should have received a copy of the GNU General Public License
      along with libextractor; see the file COPYING.  If not, write to the
      Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
      Boston, MA 02110-1301, USA.
  */
 /**
  * @file plugins/thumbnailgtk_extractor.c
  * @author Christian Grothoff
  * @brief this extractor produces a binary (!) encoded
  * thumbnail of images (using gdk pixbuf).  The bottom
  * of the file includes a decoder method that can be used
  * to reproduce the 128x128 PNG thumbnails.  We use
  * libmagic to test if the input data is actually an
  * image before trying to give it to gdk-pixbuf.
  */
 #include "platform.h"
 #include "extractor.h"
 #include <magic.h>
 #include <glib.h>
 #include <gdk-pixbuf/gdk-pixbuf.h>
 
 /**
  * Target size for the thumbnails (width and height).
  */
 #define THUMBSIZE 128
 
 /**
  * Maximum image size supported (to avoid unreasonable
  * allocations)
  */
 #define MAX_IMAGE_SIZE (32 * 1024 * 1024)
 
 
 /**
  * Global handle to MAGIC data.
  */
 static magic_t magic;
 
 
 /**
  * Main method for the gtk-thumbnailer plugin.
  *
  * @param ec extraction context
  */
 void
 EXTRACTOR_thumbnailgtk_extract_method (struct EXTRACTOR_ExtractContext *ec)
 {
   GdkPixbufLoader *loader;
   GdkPixbuf *in;
   GdkPixbuf *out;
   size_t length;
   char *thumb;
   unsigned long width;
   unsigned long height;
   char format[64];
   void *data;
   uint64_t size;
   size_t off;
   ssize_t iret;
   void *buf;
   const char *mime;
 
   if (-1 == (iret = ec->read (ec->cls,
                               &data,
                               16 * 1024)))
     return;
   if (NULL == (mime = magic_buffer (magic, data, iret)))
     return;
   if (0 != strncmp (mime,
                     "image/",
                     strlen ("image/")))
     return; /* not an image */
 
   /* read entire image into memory */
   size = ec->get_size (ec->cls);
   if (UINT64_MAX == size)
     size = MAX_IMAGE_SIZE; /* unknown size, cap at max */
   if (size > MAX_IMAGE_SIZE)
     return; /* FAR too big to be an image */
   if (NULL == (buf = malloc (size)))
     return; /* too big to fit into memory on this system */
 
   /* start with data already read */
   memcpy (buf, data, iret);
   off = iret;
   while (off < size)
   {
     iret = ec->read (ec->cls, &data, size - off);
     if (iret <= 0)
     {
       /* io error */
       free (buf);
       return;
     }
     memcpy (buf + off, data, iret);
     off += iret;
   }
 
   loader = gdk_pixbuf_loader_new ();
   gdk_pixbuf_loader_write (loader,
                            buf,
                            size, NULL);
   free (buf);
   in = gdk_pixbuf_loader_get_pixbuf (loader);
   gdk_pixbuf_loader_close (loader, NULL);
   if (NULL == in)
   {
     g_object_unref (loader);
     return;
   }
   g_object_ref (in);
   g_object_unref (loader);
   height = gdk_pixbuf_get_height (in);
   width = gdk_pixbuf_get_width (in);
   snprintf (format,
             sizeof (format),
             "%ux%u",
             (unsigned int) width,
             (unsigned int) height);
   if (0 != ec->proc (ec->cls,
                      "thumbnailgtk",
                      EXTRACTOR_METATYPE_IMAGE_DIMENSIONS,
                      EXTRACTOR_METAFORMAT_UTF8,
                      "text/plain",
                      format,
                      strlen (format) + 1))
   {
     g_object_unref (in);
     return;
   }
   if ((height <= THUMBSIZE) && (width <= THUMBSIZE))
   {
     g_object_unref (in);
     return;
   }
   if (height > THUMBSIZE)
   {
     width = width * THUMBSIZE / height;
     height = THUMBSIZE;
   }
   if (width > THUMBSIZE)
   {
     height = height * THUMBSIZE / width;
     width = THUMBSIZE;
   }
   if ( (0 == height) || (0 == width) )
   {
     g_object_unref (in);
     return;
   }
   out = gdk_pixbuf_scale_simple (in, width, height,
                                  GDK_INTERP_BILINEAR);
   g_object_unref (in);
   thumb = NULL;
   length = 0;
   if (NULL == out)
     return;
   if (! gdk_pixbuf_save_to_buffer (out, &thumb,
                                    &length,
                                    "png", NULL,
                                    "compression", "9",
                                    NULL))
   {
     g_object_unref (out);
     return;
   }
   g_object_unref (out);
   if (NULL == thumb)
     return;
   ec->proc (ec->cls,
             "thumbnailgtk",
             EXTRACTOR_METATYPE_THUMBNAIL,
             EXTRACTOR_METAFORMAT_BINARY,
             "image/png",
             thumb, length);
   free (thumb);
 }
 
 
 /**
  * This plugin sometimes is installed under the alias 'thumbnail'.
  * So we need to provide a second entry method.
  *
  * @param ec extraction context
  */
 void
 EXTRACTOR_thumbnail_extract_method (struct EXTRACTOR_ExtractContext *ec)
 {
   EXTRACTOR_thumbnailgtk_extract_method (ec);
 }
 
 
 /**
  * Initialize glib and load magic file.
  */
 void __attribute__ ((constructor))
 thumbnailgtk_gobject_init ()
 {
 #if ! GLIB_CHECK_VERSION (2, 35, 0)
   g_type_init ();
 #endif
   magic = magic_open (MAGIC_MIME_TYPE);
   if (0 != magic_load (magic, NULL))
   {
     /* FIXME: how to deal with errors? */
   }
 }
 
 
 /**
  * Destructor for the library, cleans up.
  */
 void __attribute__ ((destructor))
 thumbnailgtk_ltdl_fini ()
 {
   if (NULL != magic)
   {
     magic_close (magic);
     magic = NULL;
   }
 }
 
 
 /* end of thumbnailgtk_extractor.c */