[NiLuJe]

Another small patch that follows this Calibre commit, because I managed to dig up a file like this (one of the very first Kindle book I purchased, an old Mobi v6 file), and, yep, KindleUnpack blows up on it .

(The patch from #563 is folded into this, because I'm lazy )

--- KindleUnpack_v62-ori/lib/kindleunpack.py	2013-04-22 22:04:34.000000000 +0200
+++ KindleUnpack_v62-patch/lib/kindleunpack.py	2013-09-19 19:25:29.674186532 +0200
@@ -1006,6 +1006,10 @@ class MobiHeader:
                         addValue(name, str(value))
                     elif size == 12:
                         value, = struct.unpack('>L',content)
+                        # Handle NULL ptr for *Offset...
+                        if name[-6:] == 'Offset':
+                            if value == 0xffffffff:
+                                value = 0
                         addValue(name, str(value))
                     else:
                         addValue(name, content.encode('hex'))
@@ -1229,6 +1233,16 @@ def process_all_mobi_headers(files, sect
             # if reach here should be an image but double check to make sure
             # Get the proper file extension
             imgtype = imghdr.what(None, data)
+            # imghdr only checks for JFIF or Exif JPEG files. Apparently, there are some with only the magic JPEG bytes out there...
+            # ImageMagick handle those, so, do it too.
+            if imgtype is None and data[0:2] == b'\xFF\xD8':
+                # Get last non-null bytes
+                last = len(data)
+                while (data[last-1:last] == b'\x00'):
+                    last-=1
+                # Be extra safe, check the trailing bytes, too.
+                if data[last-2:last] == b'\xFF\xD9':
+                    imgtype = "jpeg"
             if imgtype is None:
                 print "Warning: Section %s does not contain a recognised resource" % i
                 imgnames.append(None)