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+<HTML>
+<HEAD>
+<TITLE>
+ Changes in TIFF v4.0.0
+</TITLE>
+</HEAD>
+
+<BODY BGCOLOR=white>
+<FONT FACE="Helvetica, Arial, Sans">
+<FONT FACE="Helvetica, Arial, Sans">
+
+<BASEFONT SIZE=4>
+<B><FONT SIZE=+3>T</FONT>IFF <FONT SIZE=+2>C</FONT>HANGE <FONT SIZE=+2>I</FONT>NFORMATION</B>
+<BASEFONT SIZE=3>
+
+<UL>
+<HR SIZE=4 WIDTH=65% ALIGN=left>
+<B>Current Version</B>: v4.0.0<BR>
+<B>Previous Version</B>: <A HREF=v3.9.5.html>v3.9.5</a><BR>
+<B>Master FTP Site</B>: <A HREF="ftp://ftp.remotesensing.org/pub/libtiff">
+ftp.remotesensing.org</a>, directory pub/libtiff</A><BR>
+<B>Master HTTP Site</B>: <A HREF="http://download.osgeo.org/libtiff">
+http://download.osgeo.org/libtiff</a>
+<HR SIZE=4 WIDTH=65% ALIGN=left>
+</UL>
+
+<P>
+This document describes the changes made to the software between the
+<I>previous</I> and <I>current</I> versions (see above). If you don't
+find something listed here, then it was not done in this timeframe, or
+it was not considered important enough to be mentioned. Please consult
+the ChangeLog file in the source package for full change details. The
+following information is located here:
+<UL>
+<LI><A HREF="#hightlights">Major Changes</A>
+<LI><A HREF="#configure">Changes in the software configuration</A>
+<LI><A HREF="#libtiff">Changes in libtiff</A>
+<LI><A HREF="#tools">Changes in the tools</A>
+<LI><A HREF="#contrib">Changes in the contrib area</A>
+</UL>
+<p>
+<P><HR WIDTH=65% ALIGN=left>
+
+<!--------------------------------------------------------------------------->
+
+<P><A NAME="highlights"><B><FONT SIZE=+3>M</FONT>AJOR CHANGES:</B></A></P>
+
+BigTIFF support changes:
+
+<UL>
+
+ <LI>The options parameter in the TIFFOpen and TIFFClientOpen funcs has
+ been extended. When creating new files, you can add option '4' to
+ specify you want to create a ClassicTIFF file, though that is the
+ default and the option is not strictly necessary. (As such, old
+ calling code will continue to function and create ClassicTIFF files.)
+ Or you can add option '8' to specify you want to create a BigTIFF file
+ instead. This new option is also reflected in some of the tools we
+ already upgraded. For instance, you can use the -8 option on tiffcp to
+ have tiffcp produce BigTIFF files instead of the default ClassicTIFF.
+ (Whilst on additional option is provided for version selection when
+ creating new files, no such option is necessary when reading TIFF
+ files. LibTiff reads ClassicTIFF and BigTIFF both, and the application
+ does not need to be aware which TIFF version an opened file is.)
+
+ <LI>Although the tag count in BigTIFF is 64bit, we restricted the
+ count in the implementation to a much more reasonable size. This is
+ necessary in current implementation, because all tag data gets read
+ automatically in the IFD reading stage, so if there's half a dozen
+ private tags with multiple gigabytes of data that causes considerable
+ overhead even if the application level is never interested in these
+ tags. Our choice to ignore tags with data longer then a certain sanity
+ value is much needed as things stand. We also recommend to step away
+ from writing tiles that are 8 kilobyte in their uncompressed form, or
+ writing single-line strips, in really big files, resulting in mega's
+ of tiles or strips. It's much more efficient to choose bigger tile or
+ strip sizes, up to several megabyte if needed, and have a few kilo of
+ tiles or strips instead.
+
+ <LI>Although it's rare, some application code does directly access
+ file offsets. Some of these are automatically upgraded because they
+ used the toff_t type, others need to be aware that the datatype
+ changed and need to start using toff_t or uint64. This impacts access
+ to tags like the EXIF IFD tag, for example, or the SubIfds tag, or to
+ StripOffsets or TileOffsets, the return type of functions like
+ TIFFCurrentDirOffset, and a parameter type to functions like
+ TIFFSetSubDirectory.
+
+ <LI>Although it's rare, some application code does use structures
+ like TIFFHeader or TIFFDirEntry that used to be an exact binary
+ representation of TIFF structures. These need to change. The old
+ TIFFHeader structure is replaced by the new TIFFHeaderClassic,
+ TIFFHeaderBig, and TIFFHeaderCommon structures that are an exact
+ binary representation of the ClassicTIFF and BigTIFF header, and of
+ the part that is common to both. There is no new equivalent for the
+ old TIFFDirEntry structure (or more precisely, there is still a
+ TIFFDirEntry structure, but it is changed, moved to library-private
+ definition, and no longer an exact binary representation of the tag
+ structure of either TIFF version).
+
+ <LI>Sizer functions, like TIFFTileSize or TIFFScanlineSize and the
+ like, return a tmsize_t value (tmsize_t is defined as int32 on 32bit
+ machines, and int64 on 64bit machines, and as such it is meant to
+ represent signed memory sizes). This is because we figure 98% of the
+ calling code uses the return value as sizes in allocations and the
+ like. So, any overflow that is theoretically possible with BigTIFF
+ when LibTiff is running on a 32bit system, is best detected inside the
+ sizer functions and it is best to return a type that makes sense as a
+ memory size. If your calling code is the exception and is interested
+ in actual file size, you best use the newer TIFFTileSize64 or
+ TIFFScanlineSize64 function that returns an uint64 type.
+
+ <LI>These TIFF tags require a 64-bit type as an argument in
+ libtiff 4.0.0:
+ <UL>
+ <LI> TIFFTAG_FREEBYTECOUNTS
+ <LI> TIFFTAG_FREEOFFSETS
+ <LI> TIFFTAG_STRIPBYTECOUNTS
+ <LI> TIFFTAG_STRIPOFFSETS
+ <LI> TIFFTAG_TILEBYTECOUNTS
+ <LI> TIFFTAG_TILEOFFSETS
+ </UL>
+
+</UL>
+
+Other important backward incompatible changes in the public API:
+
+<UL>
+ <LI> TIFFRewriteField() renamed into _TIFFRewriteField() and moved out
+ from the public interface (from tiffio.h to tiffiop.h). Type of its
+ 'count' parameter changed from uint32 to tmsize_t.
+
+ <LI> TIFFMergeFieldInfo() returns non-void result now. It returns 0
+ if successful and -1 if failed. Though this is now obsoleted function
+ and should not be used in new programs. Use the new tag extension
+ scheme instead.
+
+ <LI> TIFFFieldWithTag() and TIFFFieldWithName() functions now return
+ pointer to TIFFField constant object instead of TIFFFieldInfo.
+
+ <LI> TIFFReassignTagToIgnore() function and TIFFIgnoreSense enumeration
+ have been removed. They was unused and never been used properly.
+ Should be unneeded for high-level applications.
+
+ <LI> TIFFTagValue structure removed from the public tiffio.h
+ to private tif_dir.h and not accessible anymore. It should be unneeded
+ for high-level applications.
+
+</UL>
+
+<P><HR WIDTH=65% ALIGN=left>
+<!--------------------------------------------------------------------------->
+
+<P><A NAME="configure"><B><FONT SIZE=+3>C</FONT>HANGES IN THE SOFTWARE CONFIGURATION:</B></A></P>
+
+<UL>
+
+ <LI>Updated autotools: Autoconf 2.68, Automake 1.11.1, libtool
+ 2.4.
+
+ <LI>Enabled support for Automake silent build rules
+ (--enable-silent-rules or 'make V=0')
+
+ <LI>Enabled support for Automake colorized and parallel tests.
+
+ <LI>Added detection of 64-bit integer types since libtiff 4.0
+ requires use of 64-bit signed and unsigned integer types.
+
+ <LI>Libtiff now provides a more comprehensive test suite with
+ over 72 tests, which may be executed on Unix-like systems, or
+ under Microsoft Windows using MinGW/MSYS or Cygwin.
+
+ <LI>--disable-lzma configure option to disable use of liblzma.
+
+ <LI>--enable-defer-strile-load configure option to enable
+ experimental deferred strip/tile offset/size loading. May
+ cause some extremely sophisticated uses of libtiff to fail.
+
+ <LI>--enable-chunky-strip-read configure option to enable
+ experimental enable reading large strips in chunks in
+ TIFFReadScanline().
+
+ <LI>Now always uses WIN32 native I/O functions for Microsoft
+ Windows except for under Cygwin.
+
+ <LI>Now provides a pkg-config support file (libtiff-4.pc).
+
+</UL>
+
+<P><HR WIDTH=65% ALIGN=left>
+
+<!--------------------------------------------------------------------------->
+
+<P><A NAME="libtiff"><B><FONT SIZE=+3>C</FONT>HANGES IN LIBTIFF:</B></A></P>
+
+<UL>
+
+ <LI>Patches/fixes made to stable libtiff (v3.9.X) are also
+ applied to 4.0.0. There are too many to list here. See the
+ distribution ChangeLog for a detailed change list.
+
+ <LI>There is considerable change in some files like
+ tif_dirread and tif_dirwrite. These changes don't impact
+ backwards compatibility, they are mostly a clean rewrite that
+ does allow BigTIFF support as well as somewhat more robust
+ reading of the unexpected already and will also serve future
+ API extension but does not impact current API or functionality
+ in a negative way that you need to know about.
+
+ <LI>Although there is still a functional definition for types
+ like toff_t (file offset), tstrip_t (strip index number), etc,
+ we recommend against using these in newer code. We have
+ learned that it is next to impossible to use these
+ consistently and make real abstraction of the binary format of
+ these types. Instead, at a certain level we always end up
+ doing casts anyway, and taking the exact binary format into
+ account, so these types are nothing but dangerously misleading
+ and obfuscating. You do not need to update calling code that
+ uses them, as 99.9% of such code will continue to work. But we
+ recommend against using them in newer calling code, and we
+ started replacing them with binary clear types like uint16,
+ uint32 and such in the library.
+
+ <LI>We do use and will continue to use one functional type
+ that is an exception to the above rule, being tmsize_t. This
+ is a signed memory size type, i.e. it is int32 on 32bit
+ machines, or int64 on 64bit machines.
+
+ <LI>Optionally support LZMA compression via TIFF tag 34925.
+ Tiffcp supports compression levels similar to "-c lzma:p1" or
+ "-c zip:p9 for setting the LZMA compression parameters.
+
+ <LI>Optionally defer the load of strip/tile offset and size
+ tags for optimized scanning of directories. Enabled with the
+ --enable-defer-strile-load configure option (DEFER_STRILE_LOAD
+ #define in tif_config.h).
+
+ <LI>Optionally enable experimental support for reading big
+ strips in chunks. Enabled with the --enable-chunky-strip-read
+ configure option.
+
+</UL>
+
+<P><HR WIDTH=65% ALIGN=left>
+
+<!-------------------------------------------------------------------------->
+
+<P><A NAME="tools"><B><FONT SIZE=+3>C</FONT>HANGES IN THE TOOLS:</B></A></P>
+
+<UL>
+
+ <LI>tiffset: add -d and -sd switches to allow operation on
+ a particular directory, not just the first.
+
+</UL>
+
+<P><HR WIDTH=65% ALIGN=left>
+
+<!--------------------------------------------------------------------------->
+
+<P><A NAME="contrib"><B><FONT SIZE=+3>C</FONT>HANGES IN THE CONTRIB AREA:</B></A></P>
+
+<UL>
+</UL>
+
+Last updated $Date: 2011-04-09 21:01:00 $.
+
+</BODY>
+</HTML>