
Libpng 1.7.0beta54 - March 4, 2015

This is not intended to be a public release.  It will be replaced
within a few weeks by a public version or by another test version.

Files available for download:

Source files with LF line endings (for Unix/Linux) and with a
"configure" script

   1.7.0beta54.tar.xz (LZMA-compressed, recommended)
   1.7.0beta54.tar.gz

Source files with CRLF line endings (for Windows), without the
"configure" script

   lp170b54.7z  (LZMA-compressed, recommended)
   lp170b54.zip

Other information:

   1.7.0beta54-README.txt
   1.7.0beta54-LICENSE.txt
   libpng-1.7.0beta54-*.asc (armored detached GPG signatures)

Changes since the last public release (1.6.0):

Version 1.7.0alpha01 [December 15, 2012]
  Started 1.7.0 branch from libpng-1.6.0beta33.
  Made 8-bit compose and rgb_to_grayscale accuracy improvements.  These
    changes cause 16-bit arithmetic to be used for 8-bit data in the gamma
    corrected compose and grayscale operations.  The arithmetic errors have
    three sources all of which are fixed in this commit:
    1) 8-bit linear calculations produce massive errors for lower intensity
       values.
    2) The old 16-bit "16 to 8" gamma table code erroneously wrote the lowest
       output value into a table entry which corresponded to multiple output
       values (so where the value written should have been the closest to the
       transformed input value.)
    3) In a number of cases the code to access the 16-bit table did not round;
       it did a simple shift, which was wrong and made the side effects of (2)
       even worse.
  The new gamma code does not have the 16-to-8 problem at the cost of slightly
    more calculations and the algorithm used to minimize the number of
    calculations has been extended to all the 16-bit tables; it has advantages
    for any significant gamma correction.
  Rearranged png_struct, remove unused members, change png_set_filter handling
    png_struct members rearranged - partly to reorder to avoid packing, partly
    to put frequently accessed members at the start and partly to make
    the grouping more clear. png_set_filter code has been rewritten and the
    code shared with png_write_start_row moved to a common function.  Comments
    in png.h have been made more clear. Minor fixes to
    contrib/libtests/timepng.c and some of the png_*_tRNS logic, including
    more error detection in png_set_tRNS.
  Cleaned up USER_LIMITS feature, removing members from png_struct when not
    required.
  Rearranged ARM-NEON optimizations to isolate the machine specific code to
    the hardware subdirectory, and add comments to pngrutil.c so that
    implementors of other optimizations will know what to do.
  Fixed cases of unquoted DESTDIR in Makefile.am.
  Rebuilt Makefile.in, configure, etc., with autoconf-2.69 and automake-1.12.5.

Version 1.7.0alpha02 [December 17, 2012]
  Removed functions that were deprecated in libpng-1.6.0:
    png_reset_zstream(), png_info_init_3(), and png_data_freer() and its
    associated flags.
  Removed some duplicated lines from contrib/tools/scale.c and png.c.
  Changed some instances of png_warning() to png_app_error().
  Updated some left over "1.6.0beta32" in code sources.
  Fixed a "png_structp" prototype (should be png_structrp) in arm_init.c
  Updated the version-number hack in pngvalid.c

Version 1.7.0alpha03 [December 19, 2012]
  Cleaned up and enhanced the configure option; libpng now correctly
    links and tests against zlib with a prefix; tests have been clarified; and
    irrelevant or obsolete things (as defined by the autotools man page) have
    been removed.
  Documented new PNG_ABORT behavior in the manual and commentary in pngerror.c
  Cleaned up whitespace in the synopsis portion of the manpage "libpng.3"
  Fixed previous support for Z_PREFIX in configure builds, corrected sCAL APIs;
    some of these use floating point arithmetic so they need to be disabled if
    floating point arithmetic is switched off.  This is a quiet API change -
    previously it appeared that the APIs were supported if fixed point
    arithmetic was used internally, however they required certain APIs (floor,
    modf, frexp, atof) that are part of C floating point support. Changed
    png_fixed and the gamma code specific version of the same to avoid floor(),
    which may be a library function (not an intrinsic). Removed unused #if 0
    code.
  Disassembled the version number in scripts/options.awk (necessary for
    building on SunOs).

Version 1.7.0alpha04 [December 23, 2012]
  Added scripts/makefile.msys contributed by Christopher M. Wheeler
  Made default Zlib compression settings be configurable. This adds #defines to
    pnglibconf.h to control the defaults.
  Fixed Windows build issues, enabled ARM compilation. Various warnings issued
    by earlier versions of GCC fixed for Cygwin and Min/GW (which both use old
    GCCs.) ARM support is enabled by default in zlib.props (unsupported by
    Microsoft) and ARM compilation is made possible by deleting the check for
    x86. The test programs cannot be run because they are not signed.

Version 1.7.0alpha05 [December 24, 2012]
  Discontinued distributing libpng-1.x.x.tar.bz2.
  Discontinued distributing libpng-1.7.0-1.6.0-diff.txt and similar.

Version 1.7.0alpha06 [January 1, 2013]
  Fixed 'make distcheck' on SUN OS - libpng.so was not being removed

Version 1.7.0alpha07 [January 10, 2013]
  Fixed conceivable but difficult to repro overflow. Also added two test
    programs to generate and test a PNG which should have the problem.

Version 1.7.0alpha08 [January 17, 2013]
  Corrected previous attempt at overflow detection in png_set_unknown_chunks()
  (CVE-2013-7353).  Added overflow detection in png_set_sPLT() and
  png_set_text_2() (CVE-2013-7354).

Version 1.7.0alpha09 [January 21, 2013]
  Pulled changes to multi-chunk handling from libpng-1.6.0beta40.

Version 1.7.0alpha10 [February 5, 2013]
  Make symbol prefixing work with the ARM neon optimizations. Also
    allow pngpriv.h to be included for preprocessor definitions only, so
    it can be used in non-C/C++ files.
  Added png_get_palette_max() function.
  Changed png_size_t to size_t throughout headers, make sRGB check numbers
    consistent.
  Fixed ARM support (Mans Rullgard).
  Removed stray out-of-order #endif and #ifdef (Mans Rullgard).
  Ported libpng 1.5 options.awk/dfn file handling to 1.7, fixed one bug.
  Rebuilt Makefile.in, configure, etc., with autoconf-2.69 and automake-1.13.
  Minor fixes to assembler changes, verified with a dummy .S file
  Removed cc -E workround, corrected png_get_palette_max API. Tested on
    SUN OS cc 5.9, which demonstrates the tokenization problem previously
    avoided by using /lib/cpp.  Since all .dfn output is now protected
    in double quotes unless it is to be macro substituted the fix should work
    everywhere.

Version 1.7.0beta01 [February 15, 2013]
  Enable parallel tests and rearrange TESTS order to take advantage of
    the massive speed improvements use a make capable of parallel builds
    on a multi-CPU machine and pass the right arguments to make (-j10000
    for GNU make) to get the build to run in parallel.
  Fixed previous support for Z_PREFIX in configure builds, corrected
    sCAL APIs; some of these use floating point arithmetic so need to be
    disabled if floating point arithmetic is switched off.  This is a quiet API
    change - previously it appeared that the APIs were supported if fixed point
    arithmetic was used internally, however they required certain APIs (floor,
    modf, frexp, atof) that are part of C floating point support. Changed
    png_fixed and the gamma code specific version of the same to avoid floor(),
    which may be a library function (not an intrinsic). Removed unused #if 0
    code.
  Fixed make distcheck to skip over the test result files. They were
    being included because the whole of the 'tests' directory is included,
    fixed to just include the actual test files and tests/pngstest.  Also
    reverted the previous erroneous change to remove the ${srcdir} from the
    front of contrib, scripts, projects and added an explanation of what is
    going on to Makefile.am
  Fixed missing dependency in --prefix builds. The intermediate
    internal 'prefix.h' file can only be generated correctly after pnglibconf.h,
    however the dependency was not in Makefile.am.  The symptoms are
    unpredictable depending on the order make chooses to build pngprefix.h and
    pnglibconf.h, often the error goes unnoticed because there is a system
    pnglibconf.h to use instead.
  Accept "," as a separator in pnglibconf.dfa and allow for
    continuation lines. This adds to the syntax of "option" and "chunk" lines,
    allowing the elements to be separated by a "," at the end of an element and
    interpreting a "," at end of line as a continuation - so the following line
    is read.  The new syntax is optional and solely provided for readability.
  Enclosed the new png_get_palette_max in #ifdef PNG_GET_PALETTE_MAX_SUPPORTED
    block, and revised pnglibconf.h and pnglibconf.h.prebuilt accordingly.

Version 1.7.0beta02 [February 18, 2013]
  Fixed a race condition in the creation of the build 'scripts' directory
    while building with a parallel make.
  Use approved/supported Android method to check for NEON, use Linux/POSIX
    1003.1 API to check /proc/self/auxv avoiding buffer allocation and other
    library calls (ported from libpng15).
  Use parentheses more consistently in "#if defined(MACRO)" tests.
  Folded long lines.

Version 1.7.0beta03 [February 22, 2013]
  Reenabled code to allow zero length PLTE chunks for MNG.
  Fixed ALIGNED_MEMORY support.
  Allow run-time ARM NEON checking to be disabled. A new configure option:
    --enable-arm-neon=always will stop the run-time checks. New checks
    within arm/arm_init.c will cause the code not to be compiled unless
    __ARM_NEON__ is set. This should make it fail safe (if someone asks
    for it on then the build will fail if it can't be done.)
  Updated the INSTALL document.

Version 1.7.0beta04 [February 27, 2013]
  Revised INSTALL to recommend using CPPFLAGS instead of INCLUDES.
  Revised scripts/makefile.freebsd to respect ZLIBLIB and ZLIBINC.
  Revised scripts/dfn.awk to work with the buggy MSYS awk that has trouble
    with CRLF line endings.

Version 1.7.0beta05 [March 5, 2013]
  Avoid a possible memory leak in contrib/gregbook/readpng.c
  Changed user chunk callback API to respect global and per chunk defaults.
    Previously a return of 0 from a user chunk callback would result in the
    chunk being saved (if this was safe, even if the chunk was unsafe-to-copy);
    this change respects the defaults set by the application, so unknown chunks
    can be discarded by default and known-safe ones preserved.
  Corrected Android builds and corrected libpng.vers with symbol
    prefixing. This adds an API to set optimization options externally,
    providing an alternative and general solution for the non-portable
    run-time tests used by the ARM Neon code.  It also makes those tests
    compile and link on Android.  The order of settings vs options in
    pnglibconf.h is reversed to allow settings to depend on options and
    options can now set (or override) the defaults for settings.

Version 1.7.0beta06 [March 13, 2013]
  Corrected simplified API default gamma for color-mapped output, added
    a flag to change default. In 1.6.0 when the simplified API was used
    to produce color-mapped output from an input image with no gamma
    information the gamma assumed for the input could be different from
    that assumed for non-color-mapped output.  In particular 16-bit depth
    input files were assumed to be sRGB encoded, whereas in the 'direct'
    case they were assumed to have linear data.  This was an error.  The
    fix makes the simplified API treat all input files the same way and
    adds a new flag to the png_image::flags member to allow the
    application/user to specify that 16-bit files contain sRGB data
    rather than the default linear.
  Fixed bugs in the pngpixel and makepng test programs.
  Fixed CMakelists.txt to allow building a single variant of the library
    (Claudio Bley):
  Introduced a PNG_LIB_TARGETS variable that lists all activated library
    targets.  It is an error if this variable ends up empty, ie. you have
    to build at least one library variant.
  Made the *_COPY targets only depend on library targets actually being build.
  Use PNG_LIB_TARGETS to unify a code path.
  Changed the CREATE_SYMLINK macro to expect the full path to a file as the
    first argument. When symlinking the filename component of that path is
    determined and used as the link target.
  Use copy_if_different in the CREATE_SYMLINK macro.
  Eliminated two warnings from the Intel C compiler. The warnings are
    technically valid, although a reasonable treatment of division would
    show it to be incorrect.

Version 1.7.0beta07 [April 14, 2013]
  Updated documentation of 1.5.x to 1.6.x changes in iCCP chunk handling.
  Fixed incorrect warning of excess deflate data. End condition - the
    warning would be produced if the end of the deflate stream wasn't read
    in the last row.  The warning is harmless.
  Corrected the test on user transform changes on read. It was in the
    png_set of the transform function, but that doesn't matter unless the
    transform function changes the rowbuf size, and that is only valid if
    transform_info is called.
  Corrected a misplaced closing bracket in contrib/libtests/pngvalid.c
    (Flavio Medeiros).
  Corrected length written to uncompressed iTXt chunks (Samuli Suominen).

Version 1.7.0beta08 [April 18, 2013]
  Added contrib/tools/fixitxt.c, to repair the erroneous iTXt chunk length
    written by libpng-1.6.0 and 1.6.1.
  Disallow storing sRGB information when the sRGB is not supported.

Version 1.7.0beta09 [April 24, 2013]
  Exposed PNG chunk types in png.h
  Modified png_uint_32 macros/code to make as few assumptions as possible
  Revised stack marking in arm/filter_neon.S and configure.ac
  Ensure that NEON filter stuff is completely disabled when switched 'off'.
    Previously the ARM NEON specific files were still built if the option
    was switched 'off' as opposed to being explicitly disabled.

Version 1.7.0beta10 [April 24, 2013]
  Attempt to fix the PNG_ARM_NEON configuration mess.

Version 1.7.0beta11 [April 26, 2013]
  Test for 'arm*', not just 'arm' in the host_cpu configure variable.

Version 1.7.0beta12 [April 30, 2013]
  Added png_app_warning for out-of-range unknown chunk index in
    png_set_unknown_chunk_location().
  Expanded manual paragraph about writing private chunks.
  Avoid dereferencing NULL pointer possibly returned from
     png_create_write_struct() (Andrew Church).

Version 1.7.0beta13 [May 12, 2013]
  Revised contrib/pngminim/*/makefile to generate pnglibconf.h with the
    right zlib header files.
  Separated CPPFLAGS and CFLAGS in contrib/pngminim/*/makefile
  Updated contrib/pngminus/pnm2png.c (Paul Stewart):
    Check for EOF
    Ignore "#" delimited comments in input file to pnm2png.c.
    Fixed whitespace handling
    Added a call to png_set_packing()
    Initialize dimension values so if sscanf fails at least we have known
      invalid values.
  Calculate our own zlib windowBits when decoding rather than trusting the
    CMF bytes in the PNG datastream.
  Added an option to force maximum window size for inflating, which was
    the behavior of libpng15 and earlier.
  Added png-fix-itxt and png-fix-too-far-back to the built programs and
    removed warnings from the source code and timepng that are revealed as
    a result.
  Detect wrong libpng versions linked to png-fix-too-far-back, which currently
    only works with libpng versions that can be made to reliably fail when
    the deflate data contains an out-of-window reference.  This means only
    1.6 and later.
  Attempt to detect configuration issues with png-fix-too-far-back, which
    requires both the correct libpng and the correct zlib to function
    correctly.
  Check ZLIB_VERNUM for mismatches, enclose #error in quotes
  Added information in the documentation about problems with and fixes for
    the bad CRC and bad iTXt chunk situations.

Version 1.7.0beta14 [June 8, 2013]
  Removed a redundant test in png_set_IHDR().
  Added set(CMAKE_CONFIGURATION_TYPES ...) to CMakeLists.txt (Andrew Hundt)
  Deleted set(CMAKE_BUILD_TYPE) block from CMakeLists.txt
  Enclose the prototypes for the simplified write API in #ifdef STDIO/#endif
  Make ARM NEON support work at compile time (not just configure time).
    This moves the test on __ARM_NEON__ into pngconf.h to avoid issues when
    using a compiler that compiles for multiple architectures at one time.
  Removed PNG_FILTER_OPTIMIZATIONS and PNG_ARM_NEON_SUPPORTED from
    pnglibconf.h, allowing more of the decisions to be made internally
    (pngpriv.h) during the compile.  Without this, symbol prefixing is broken
    under certain circumstances on ARM platforms.  Now only the API parts of
    the optimizations ('check' vs 'api') are exposed in the public header files
    except that the new setting PNG_ARM_NEON_OPT documents how libpng makes the
    decision about whether or not to use the optimizations.
  Protect symbol prefixing against CC/CPPFLAGS/CFLAGS useage.
    Previous iOS/Xcode fixes for the ARM NEON optimizations moved the test
    on __ARM_NEON__ from configure time to compile time.  This breaks symbol
    prefixing because the definition of the special png_init_filter_functions
    call was hidden at configure time if the relevant compiler arguments are
    passed in CFLAGS as opposed to CC.  This change attempts to avoid all
    the confusion that would result by declaring the init function even when
    it is not used, so that it will always get prefixed.

Version 1.7.0beta15 [June 18, 2013]
  Revised libpng.3 so that "doclifter" can process it.

Version 1.7.0beta16 [July 5, 2013]
  Revised example.c to illustrate use of PNG_DEFAULT_sRGB and PNG_GAMMA_MAC_18
    as parameters for png_set_gamma().  These have been available since
    libpng-1.5.4.
  Renamed contrib/tools/png-fix-too-far-back.c to pngfix.c and revised it
    to check all compressed chunks known to libpng.
  Updated documentation to show default behavior of benign errors correctly.
  Added perfect hash code generation for lists of PNG chunks. This is
    a work in progress; checked in for use in pngfix.c
  Ported ARM no-read patch from libpng16.
  Ported pngfix.c patches from libpng16.

Version 1.7.0beta17 [August 21, 2013]
  Revised manual about changes in iTXt chunk handling made in libpng-1.6.0.
  Added "/* SAFE */" comments in pngrutil.c and pngrtran.c where warnings
    may be erroneously issued by code-checking applications.
  Added information about png_set_options() to the manual.
  Delay calling png_init_filter_functions() until a row with nonzero filter
    is found.

Version 1.7.0beta18 [September 16, 2013]
  Fixed inconsistent conditional compilation of png_chunk_unknown_handling()
    prototype, definition, and usage.  Made it depend on
    PNG_HANDLE_AS_UNKNOWN_SUPPORTED everywhere.

Version 1.7.0beta19 [September 30, 2013]
  Reverted the change to unknown handling #defines; the change breaks 'NOREAD'
    builds.
  Fixed default behavior of ARM_NEON_API. If the ARM NEON API option is
    compiled without the CHECK option it defaulted to on, not off.
  Catch up with recent libpng16 changes; unknown handling and spelling
    corrections
  Avoid up-cast warnings in pngvalid.c. On ARM the alignment requirements of
    png_modifier are greater than that of png_store and as a consequence
    compilation of pngvalid.c results in a warning about increased alignment
    requirements because of the bare cast to (png_modifier*).  The code is
    safe, because the pointer is known to point to a stack allocated
    png_modifier, but this change avoids the warning.
  Fixed some grammatical changes and updated the png chunks list.

Version 1.7.0beta20 [October 13, 2013]
  Made changes for compatibility with automake 1.14:
    1) Added the 'compile' program to the list of programs that must be cleaned
       in autogen.sh
    2) Added 'subdir-objects' which causes .c files in sub-directories to be
       compiled such that the corresponding .o files are also in the
       sub-directory.  This is because automake 1.14 warns that the
       current behavior of compiling to the top level directory may be removed
       in the future.
    3) Updated dependencies on pnglibconf.h to match the new .o locations and
       added all the files in contrib/libtests and contrib/tools that depend
       on pnglibconf.h
    4) Added 'BUILD_SOURCES = pnglibconf.h'; this is the automake recommended
       way of handling the dependencies of sources that are machine generated;
       unfortunately it only works if the user does 'make all' or 'make check',
       so the dependencies (3) are still required.
  Cleaned up (char*) casts of zlib messages. The latest version of the Intel C
    compiler complains about casting a string literal as (char*), so copied the
    treatment of z_const from the library code into pngfix.c
  Simplified error message code in pngunknown. The simplification has the
    useful side effect of avoiding a bogus warning generated by the latest
    version of the Intel C compiler (it objects to
    condition ? string-literal : string-literal).
  Make autogen.sh work with automake 1.13 as well as 1.14. Do this by always
    removing the 1.14 'compile' script but never checking for it.

Version 1.7.0beta21 [November 2, 2013]
  Added ARMv8 support (James Yu <james.yu at linaro.org>).  Added file
    arm/filter_neon_intrinsics.c; enable with -mfpu=neon.
  Revised pngvalid to generate size images with as many filters as it can
    manage, limited by the number of rows.
  Cleaned up ARM NEON compilation handling. The tests are now in pngpriv.h
    and detect the broken GCC compilers.
  Allow clang derived from older GCC versions to use ARM intrinsics. This
    causes all clang builds that use -mfpu=neon to use the intrinsics code,
    not the assembler code.  This has only been tested on iOS 7. It may be
    necessary to exclude some earlier clang versions but this seems unlikely.
  Changed NEON implementation selection mechanism. This allows assembler
    or intrinsics to be turned on at compile time during the build by defining
    PNG_ARM_NEON_IMPLEMENTATION to the correct value (2 or 1).  This macro
    is undefined by default and the build type is selected in pngpriv.h.

Version 1.7.0beta22 [November 7, 2013]
  Fixed #include in filter_neon_intrinsics.c and ctype macros. The ctype char
    checking macros take an unsigned char argument, not a signed char.

Version 1.7.0beta23 [November 24, 2013]
  Changed #ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED in pngpread.c to
    #ifdef PNG_SET_UNKNOWN_CHUNKS_SUPPORTED to be consistent with
    what is in pngpriv.h.
  Moved prototype for png_handle_unknown() in pngpriv.h outside of
    the #ifdef PNG_SET_UNKNOWN_CHUNKS_SUPPORTED/#endif block.
  Added "-Wall" to CFLAGS in contrib/pngminim/*/makefile
  Conditionally compile some unused functions reported by -Wall in
    pngminim.
  Fixed 'minimal' builds. Various obviously useful minimal configurations
    don't build because of missing contrib/libtests test programs and
    overly complex dependencies in scripts/pnglibconf.dfa. This change
    adds contrib/conftest/*.dfa files that can be used in automatic build
    scripts to ensure that these configurations continue to build.
  Enabled WRITE_INVERT and WRITE_PACK in contrib/pngminim/encoder.
  Fixed pngvalid 'fail' function declaration on the Intel C Compiler.
    This reverts to the previous 'static' implementation and works round
    the 'unused static function' warning by using PNG_UNUSED().

Version 1.7.0beta24 [December 15, 2013]
  Removed or marked PNG_UNUSED some harmless "dead assignments" reported
    by clang scan-build.
  Changed tabs to 3 spaces in png_debug macros and changed '"%s"m'
    to '"%s" m' to improve portability among compilers.
  Changed png_free_default() to free() in pngtest.c
  Tidied up pngfix inits and fixed pngtest no-write builds.
  Bookkeeping: Moved functions around (no changes). Moved transform
    function definitions before the place where they are called so that
    they can be made static. Move the intrapixel functions and the
    grayscale palette builder out of the png?tran.c files. The latter
    isn't a transform function and is no longer used internally, and the
    former MNG specific functions are better placed in pngread/pngwrite.c
  Made transform implementation functions static. This makes the internal
    functions called by png_do_{read|write}_transformations static. On an
    x86-64 DLL build (Gentoo Linux) this reduces the size of the text
    segment of the DLL by 1208 bytes, about 0.6%. It also simplifies
    maintenance by removing the declarations from pngpriv.h and allowing
    easier changes to the internal interfaces.
  Handle zero-length PLTE chunk or NULL palette with png_error()
    instead of png_chunk_report(), which by default issues a warning
    rather than an error, leading to later reading from a NULL pointer
    (png_ptr->palette) in png_do_expand_palette(). This is CVE-2013-6954
    and VU#650142.  Libpng-1.6.1 through 1.6.7 and libpng-1.7.0beta03
    through 1.7.0beta23 are vulnerable.  Libpng-1.6.0 and earlier do not
    have the bug.

Version 1.7.0beta25 [December 26, 2013]
  Merged files with version 1.6.8 that have not changed since then.
  Rebuilt configure scripts with automake-1.14.1 and autoconf-2.69

Version 1.7.0beta26 [January 1, 2014]
  Added libpng 1.5 checks to pngvalid.c
  Merged with 1.5 and 1.6 changes to create a single pngvalid.c
  Added dSIG to chunk list in png.h
  Removed #error macro from contrib/tools/pngfix.c (Thomas Klausner).
  Merged pngrio.c, pngtrans.c, and pngwio.c with libpng-1.6.9
  Fixed test programs for interlace options. Made pngvalid.c and
    pngtest.c work correctly when READ_INTERLACING and/or WRITE_INTERLACING
    are switched off.
  Changed pngvalid.c to support libpng 1.5, which does not support
    the PNG_MAXIMUM_INFLATE_WINDOW option, so #define it out when
    appropriate in pngvalid.c
  Allow unversioned links created on install to be disabled in configure.
    In configure builds 'make install' changes/adds links like png.h
    and libpng.a to point to the newly installed, versioned, files (e.g.
    libpng17/png.h and libpng17.a). Three new configure options and some
    rearrangement of Makefile.am allow creation of these links to be disabled.

Version 1.7.0beta27 [January 10, 2014]
  Removed potentially misleading warning from png_check_IHDR().

Version 1.7.0beta28 [January 20, 2014]
  Updated scripts/makefile.* to use CPPFLAGS (Cosmin).
  Added clang attribute support (Cosmin).

Version 1.7.0beta29 [January 30, 2014]
  Quiet an uninitialized memory warning from VS2013 in png_get_png().

Version 1.7.0beta30 [February 2, 2014]
  Fixed a large number of instances where PNGCBAPI was omitted from
    function definitions.
  Added pngimage test program for png_read_png and png_write_png. This
    is a work-in-progress; no tests are run automatically at present and
    the program by virtue of exhaustively testing all the transforms is
    very slow.

Version 1.7.0beta31 [February 6, 2014]
  Make png_read_png() and png_write_png() prototypes in png.h depend
    upon PNG_READ_SUPPORTED and PNG_WRITE_SUPPORTED.
  Removed dependence on !PNG_READ_EXPAND_SUPPORTED for calling
    png_set_packing() in png_read_png().
  Completed full working pngimage test program and added two test scripts.
  Fixed combination of ~alpha with shift. On read invert alpha, processing
    occurred after shift processing, which causes the final values to be
    outside the range that should be produced by the shift. Reversing the
    order on read makes the two transforms work together correctly and mirrors
    the order used on write.
  Do not read invalid sBIT chunks. Previously libpng only checked sBIT
    values on write, so a malicious PNG writer could therefore cause
    the read code to return an invalid sBIT chunk, which might lead to
    application errors or crashes.  Such chunks are now skipped (with
    chunk_benign_error).
  Restored a line, "c = b;", that was inadvertently deleted from the
    PAETH filtering code from libpng-1.7.0beta24/pngrutil.c. Deleted
    the other instance of "c = b;" which is the one that triggered a
    scan-build warning.
  Support builds with unsupported PNG_TRANSFORM_* values.  All of the
    PNG_TRANSFORM_* values are always defined in png.h and, because they
    are used for both read and write in some cases, it is not reliable
    to #if out ones that are totally unsupported. This change adds error
    detection in png_read_image() and png_write_image() to do a
    png_app_error() if the app requests something that cannot be done
    and it adds corresponding code to pngimage.c to handle such options
    by not attempting to test them.

Version 1.7.0beta32 [February 26, 2014]
  Moved redefines of png_error(), png_warning(), png_chunk_error(),
    and png_chunk_warning() from pngpriv.h to png.h to make them visible
    to libpng-calling applications.
  Moved OS dependent code from arm/arm_init.c, to allow the included
    implementation of the ARM NEON discovery function to be set at
    build-time and provide sample implementations from the current code in the
    contrib/arm-neon subdirectory. The __linux__ code has also been changed to
    compile and link on Android by using /proc/cpuinfo, and the old linux code
    is in contrib/arm-neon/linux-auxv.c.  The new code avoids POSIX and Linux
    dependencies apart from opening /proc/cpuinfo and is C90 compliant.
  Check for info_ptr == NULL early in png_read_end() so we don't need to
    run all the png_handle_*() and depend on them to return if info_ptr == NULL.
    This improves the performance of png_read_end(png_ptr, NULL) and makes
    it more robust against future programming errors.
  Check for __has_extension before using it in pngconf.h, to
    support older Clang versions (Jeremy Sequoia).
  Use a user warning handler in contrib/gregbook/readpng2.c instead of default,
    so warnings will be put on stderr even if libpng has CONSOLE_IO disabled.
  Added png_ptr->process_mode = PNG_READ_IDAT_MODE in png_push_read_chunk
    after recognizing the IDAT chunk, which avoids an infinite loop while
    reading a datastream whose first IDAT chunk is of zero-length.
    This fixes CERT VU#684412 and CVE-2014-0333.
  Don't recognize known sRGB profiles as sRGB if they have been hacked,
    but don't reject them and don't issue a copyright violation warning.
  Minor editing of contrib/arm-neon/README and contrib/examples/*.c
  Moved some documentation from png.h to libpng.3 and libpng-manual.txt

Version 1.7.0beta33 [February 27, 2014]
  Fixed typos in the manual and in scripts/pnglibconf.dfa (CFLAGS -> CPPFLAGS
    and PNG_USR_CONFIG -> PNG_USER_CONFIG).

Version 1.7.0beta34 [March 17, 2014]
  Treat CRC error handling with png_set_crc_action(), instead of with
    png_set_benign_errors(), which has been the case since libpng-1.6.0beta18.
  Use "if (value != 0)" instead of "if (value)" consistently.
  Changed ZlibSrcDir from 1.2.5 to 1.2.8 in projects/vstudio.
  Moved configuration information from the manual to the INSTALL file.

Version 1.7.0beta35 [August 6, 2014]
  Removed #if/#else/#endif from inside two pow() calls in pngvalid.c because
    they were handled improperly by Portland Group's PGI-14.1 - PGI-14.3
    when using its "__builtin_pow()" function.
  Silence 'unused parameter' build warnings (Cosmin).
  $(CP) is now used alongside $(RM_F).  Also, use 'copy' instead
    of 'cp' where applicable, and applied other minor makefile changes.
  Don't warn about invalid dimensions exceeding user limits.
  Allow an easy replacement of the default pre-built configuration
    header with a custom header, via the make PNGLIBCONF_H_PREBUILT
    macro.
  Fixed a typo in pngrutil.c, introduced in libpng-1.5.6, that interferes
    with "blocky" expansion of sub-8-bit interlaced PNG files (Eric Huss).
  Removed scripts/makefile.elf. It has not worked since libpng-1.5.0beta14
    due to elimination of the PNG_FUNCTION_EXPORT and PNG_DATA_EXPORT
    definitions from pngconf.h.
  Ensure that CMakeLists.txt makes the target "lib" directory before making
    symbolic link into it (SourceForge bug report #226 by Rolf Timmermans).
  Added opinion that the ECCN (Export Control Classification Number) for
    libpng is EAR99 to the README file.

Version 1.7.0beta36 [September 27, 2014]
  Updated scripts/makefiles from libpng-1.6.13beta04.
  Minor updates to the manual from libpng-1.6.14beta04.
  Fixed incorrect handling of the iTXt compression flag in pngrutil.c
    (bug report by Shunsaku Hirata).  Bug was introduced in libpng-1.6.0.

Version 1.7.0beta37 [September 28, 2014]
  Merged scripts/*, pngvalid.c and pngfix.c with libpng-1.6.14beta04.

Version 1.7.0beta38 [October 17, 2014]
  Added "option READ_iCCP enables READ_COMPRESSED_TEXT" to pnglibconf.dfa
  Removed unused "text_len" parameter from private function png_write_zTXt().
  Conditionally compile some code in png_deflate_claim(), when
    PNG_WARNINGS_SUPPORTED and PNG_ERROR_TEXT_SUPPORTED are disabled.
  Replaced repeated code in pngpread.c with PNG_PUSH_SAVE_BUFFER_IF_FULL.
  Added "chunk iTXt enables TEXT" and "chunk zTXt enables TEXT"
    to pnglibconf.dfa.
  Removed "option READ_COMPRESSED_TEXT enables READ_TEXT" from pnglibconf.dfa,
    to make it possible to configure a libpng that supports iCCP but not TEXT.
  Removed "option WRITE_COMPRESSED_TEXT enables WRITE_TEXT" from pnglibconf.dfa
  Only mark text chunks as written after successfully writing them.

Version 1.7.0beta39 [November 1, 2014]
  Ported cosmetic changes from libpng-1.6.15beta02.

Version 1.7.0beta40 [November 6, 2014]
  Made a one-line revision to configure.ac to support ARM on aarch64
    (bug report by Marcin Juszkiewicz, fix by John Bowler).
  Use png_get_libpng_ver(NULL) instead of PNG_LIBPNG_VER_STRING in
    example.c, pngtest.c, and applications in the contrib directory.
  Avoid out-of-bounds memory access in png_user_version_check().
  Simplified and future-proofed png_user_version_check().
  Fixed GCC unsigned int->float warnings. Various versions of GCC
    seem to generate warnings when an unsigned value is implicitly
    converted to double. This is probably a GCC bug but this change
    avoids the issue by explicitly converting to (int) where safe.
  Free all allocated memory in pngimage. The file buffer cache was left
    allocated at the end of the program, harmless but it causes memory
    leak reports from clang.
  Fixed array size calculations to avoid warnings. At various points
    in the code the number of elements in an array is calculated using
    sizeof.  This generates a compile time constant of type (size_t) which
    is then typically assigned to an (unsigned int) or (int). Some versions
    of GCC on 64-bit systems warn about the apparent narrowing, even though
    the same compiler does apparently generate the correct, in-range,
    numeric constant.  This adds appropriate, safe, casts to make the
    warnings go away.

Version 1.7.0beta41 [November 7, 2014]
  Added #ifdef PNG_16BIT_SUPPORTED/#endif around png_log16bit() and
    png_do_swap().
  Changed all "#endif /* PNG_FEATURE_SUPPORTED */" to "#endif /* FEATURE */"

Version 1.7.0beta42 [November 20, 2014]
  The macros passed in the command line to Borland make were ignored if
    similarly-named macros were already defined in makefiles. This behavior
    is different from POSIX make and other make programs.  Surround the
    macro definitions with ifndef guards (Cosmin).
  Added "-D_CRT_SECURE_NO_WARNINGS" to CFLAGS in scripts/makefile.vcwin32.
  Removed the obsolete $ARCH variable from scripts/makefile.darwin.
  Merged clang no-warning fix from libpng-1.6.13: png_digit was defined
    but never used in pngerror.c.

Version 1.7.0beta43 [December 18, 2014]
  Added ".align 2" to arm/filter_neon.S to support old GAS assemblers that
    don't do alignment correctly.
  Revised Makefile.am and scripts/*.dfn to work with MinGW/MSYS;
    renamed scripts/*.dfn to scripts/*.c (Bob Friesenhahn and John Bowler).
  Quiet a "comparison always true" warning in pngstest.c (John Bowler).

Version 1.7.0beta44 [December 23, 2014]
  Restored a test on width that was removed from png.c at libpng-1.6.9
    (Bug report by Alex Eubanks, CVE-2015-0973).
  Fixed an overflow in png_combine_row() with very wide interlaced images
    (Bug report and fix by John Bowler, CVE-2014-9495).
  Corrected the width limit calculation in png_check_IHDR().
  Removed extraneous handling of PNG_SAFE_LIMITS_SUPPORTED from pngconf.h

Version 1.7.0beta45 [December 28, 2014]
  Eliminated the PNG_SAFE_LIMITS macro and restored the 1-million-column
    and 1-million-row default limits in pnglibconf.dfa, that can be reset
    by the user at build time or run time.  This provides a more robust
    defense against DOS and as-yet undiscovered overflows.
  Removed user limits from pngfix. Also pass NULL pointers to
    png_read_row to skip the unnecessary row de-interlace stuff.
  Added testing of png_set_packing() to pngvalid.c

Version 1.7.0beta46 [January 2, 2015]
  Regenerated configure scripts in the tar distributions with libtool-2.4.4
  Implement previously untested cases of libpng transforms in pngvalid.c
  Fixed byte order in 2-byte filler, in png_do_read_filler().
  Allow user to call png_get_IHDR() with NULL arguments (Reuben Hawkins).

Version 1.7.0beta47 [January 29, 2015]
  Made the check for out-of-range values in png_set_tRNS() detect
    values that are exactly 2^bit_depth, and work on 16-bit platforms.
  Added PNG_SKIP_sRGB_CHECK_PROFILE choice for png_set_option().
  Report all IHDR errors before exiting png_check_IHDR().
  Merged some parts of libpng-1.6.17beta01 and libpng-1.7.0beta47.
  Added #ifndef __COVERITY__ where needed in png.c, pngrutil.c and
    pngset.c to avoid warnings about dead code.

Version 1.7.0beta48 [February 7, 2015]
  Work around one more Coverity-scan dead-code warning.
  Do not build png_product2() when it is unused.

Version 1.7.0beta49 [February 11, 2015]
  Combined sub_row, up_row, avg_row, and paeth_row buffers into a
    single try_row buffer.
  Added PNG_WRITE_CUSTOMIZE_COMPRESSION_SUPPORTED macro, on by default.
  Consolidated redundant code in pngwutil.c
  Deal with integer overflow of sum in pngwutil.c

Version 1.7.0beta50 [February 15, 2015]
  Combined sub_row, up_row, avg_row, and paeth_row buffers into a
    single try_row buffer and in cases where two or more of those are
    being tested, a second tst_row buffer.  This improves CPU speed
    over that achieved by libpng-1.7.0beta49.

Version 1.7.0beta51 [February 17, 2015]
  Combined similar parts of png_write_find_filter() into a png_increase_lmins()
    function.
  Display user limits in the output from pngtest.
  Replaced test for harmless integer overflow (wraparound) in pngwutil.c
    with a method that prevents overflow and does not increase cpu usage
    significantly.

Version 1.7.0beta52 [February 21, 2015]
  Added information about setjmp/simplified API interaction in the
    manual page and INSTALL file. Added information about using
    row_pointers with a single height*width*bpp allocated block
  Rebuilt configure scripts with automake-1.15 and libtool-2.4.6

Version 1.7.0beta53 [February 23, 2015]
  Restored compiling of png_reciprocal2 with PNG_NO_16BIT.

Version 1.7.0beta54 [March 4, 2015]
  Moved png_set_filter() prototype into a PNG_WRITE_SUPPORTED block
    of png.h.
  Conditionally compile a small amount of code in pngwutil.c
  Avoid runtime checks when converting integer to png_byte with
    Visual Studio (Sergey Kosarevsky)
  Merged pngwrite.c with libpng-1.6.17beta06/pngwrite.c

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