Changes in TIFF v4.2.0
======================

.. table:: References
    :widths: auto

    ======================  ==========================================
    Current Version         v4.2.0 (:tag:`v4.2.0`)
    Previous Version        :doc:`v4.1.0 <v4.1.0>`
    Master Download Site    `<https://download.osgeo.org/libtiff/>`_
    Master HTTP Site #1     `<http://www.simplesystems.org/libtiff/>`_
    Master HTTP Site #2     `<https://libtiff.gitlab.io/libtiff/>`_
    Master HTTP Site #3     `<http://libtiff.maptools.org/>`_
    ======================  ==========================================

This document provides a summary of significant changes made to the
software between the *previous* and *current* versions (see
above). A fully-detailed change summary is provided by the :file:`ChangeLog` file
included in the release package and by the Git commit history:


Major changes
-------------

* Optional support for using libdeflate is added.
* Many of the tools now support a memory usage limit.


Software configuration changes
------------------------------

* The Microsoft Windows 'nmake' build is resuscitated and provides
  a default ``HAVE_STRTOLL`` setting in 'nmake.opt' which is suitable for
  MSVC++ 14.0 ("Visual Studio 2015") and later but may be disabled in
  order to compile with earlier compiler versions.

* mingw-w64 cmake build fixes to not add libm


Library changes
---------------

* A great many issues discovered by fuzzers (via oss-fuzz and other reports) have been addressed.
* EXIF 2.32 and GPS tags and functionality have been upgraded:
  
    * Existing EXIF field definition of tags are upgraded to EXIF version 2.3.2
    * EXIF-GPS structure, tags and access functions are added as special ``CustomDirectory`` (like it was done for EXIF).
    * Reading error for FileSource and SceneType tags corrected.

* Make ``TIFFTAG_CFAPATTERN`` variable count.

* Cmake configuration fixes for big-endian targets.

* Added support for optional building against libdeflate for
  faster Zip/Deflate compression/decompression.

  We now have 2 kinds of builds with the Zip/Deflate codec:

    * zlib only
    * zlib + libdeflate

  Speed improvements in the 35%-50% range can be expected when libdeflate is used.
  Compression level up to 12 is now supported (capped to 9 when zlib is used).
  Still requires zlib for situations where libdeflate cannot be used (that
  is for scanline access, since libdeflate has no streaming mode)

  Pseudo-tag ``TIFFTAG_DEFLATE_SUBCODEC=DEFLATE_SUBCODEC_ZLIB/DEFLATE_SUBCODEC_LIBDEFLATE``
  is added to control which subcodec (zlib or libdeflate) should be used (it defaults
  of course to libdeflate, when it is available).
  This is mostly aimed at being used on the writing side, to be able to reproduce
  output of previous libtiff versions at a binary level, in situations where this would
  be really needed. Or as a safety belt in case there would be unforeseen issues
  with using libdeflate.
  It can be used to know when libdeflate is available at runtime (``DEFLATE_SUBCODEC_LIBDEFLATE``
  will be the default value in that situation).

  Of course, deflate codestreams produced by libdeflate can be read by zlib, and vice-versa.


Tools changes
-------------

* A great many issues discovered by fuzzers (via oss-fuzz and other reports) have been addressed.

* :program:`ppm2tiff`: support any bps value from 1 to 16.

* :program:`tiff2ps`, :program:`tiff2rgba`:  A default memory limit is now enforced (256MiB) and a ``-M`` option is added to allow the user to adjust the limit.

* :program:`tiff2pdf`, :program:`tiffcp`: A default memory limit is now enforced (256MiB) and a ``-m`` option is added to allow the user to adjust the limit.

* :program:`tiffcrop`: A default memory limit is now enforced (256MiB) and a ``-k`` option is added to allow the user to adjust the limit.

* :program:`tiff2pdf`: fix "raw" copy of Deflate streams.

* :program:`tiff2pdf.c`: properly calculate datasize when saving to JPEG YCbCr

* :program:`tiffcp`: disable strip chopping when trying to convert to JBIG compression


Contributed software changes
----------------------------

None