From a9b3adbad343919181e227dd0d235c31e1503385 Mon Sep 17 00:00:00 2001
From: Kovid Goyal <kovid@kovidgoyal.net>
Date: Sat, 25 Jan 2014 09:52:36 +0530
Subject: [PATCH] Edit Book: Fix extra 1x1 unused GIF image being created when
 saving and re-opening AZW3 files. Fixes #1272410 [Editing AZW3 book adds 1x1
 pixel gray gif each time](https://bugs.launchpad.net/calibre/+bug/1272410)

---
 src/calibre/ebooks/mobi/reader/mobi8.py      | 3 +++
 src/calibre/ebooks/mobi/writer2/resources.py | 2 +-
 2 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/src/calibre/ebooks/mobi/reader/mobi8.py b/src/calibre/ebooks/mobi/reader/mobi8.py
index 6536c92618..734ba17abe 100644
--- a/src/calibre/ebooks/mobi/reader/mobi8.py
+++ b/src/calibre/ebooks/mobi/reader/mobi8.py
@@ -386,6 +386,7 @@ class Mobi8Reader(object):
         return build_toc(index_entries)
 
     def extract_resources(self):
+        from calibre.ebooks.mobi.writer2.resources import PLACEHOLDER_GIF
         resource_map = []
         for x in ('fonts', 'images'):
             os.mkdir(x)
@@ -414,6 +415,8 @@ class Mobi8Reader(object):
                 if font['encrypted']:
                     self.encrypted_fonts.append(href)
             else:
+                if len(data) == len(PLACEHOLDER_GIF) and data == PLACEHOLDER_GIF:
+                    continue
                 imgtype = what(None, data)
                 if imgtype is None:
                     from calibre.utils.magick.draw import identify_data
diff --git a/src/calibre/ebooks/mobi/writer2/resources.py b/src/calibre/ebooks/mobi/writer2/resources.py
index c364e9aa58..fa5b88e7ca 100644
--- a/src/calibre/ebooks/mobi/writer2/resources.py
+++ b/src/calibre/ebooks/mobi/writer2/resources.py
@@ -14,7 +14,7 @@ from calibre.ebooks import generate_masthead
 from calibre.ebooks.oeb.base import OEB_RASTER_IMAGES
 from calibre.utils.imghdr import what
 
-PLACEHOLDER_GIF = b'GIF89a\x01\x00\x01\x00\x80\x00\x00\x00\x00\x00\xff\xff\xff!\xf9\x04\x01\x00\x00\x00\x00,\x00\x00\x00\x00\x01\x00\x01\x00@\x02\x01D\x00;'
+PLACEHOLDER_GIF = b'GIF89a\x01\x00\x01\x00\xf0\x00\x00\x00\x00\x00\xff\xff\xff!\xf9\x04\x01\x00\x00\x00\x00!\xfe calibre-placeholder-gif-for-azw3\x00,\x00\x00\x00\x00\x01\x00\x01\x00\x00\x02\x02D\x01\x00;'  # noqa
 
 class Resources(object):