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It is released under the same license as the WebM project.
See http://www.webmproject.org/license/software/ or the
file "COPYING" file for details. An additional intellectual
property rights grant can be found in the file PATENTS.

Building:
=========

Windows build:
--------------

By running:

  nmake /f Makefile.vc CFG=release-static RTLIBCFG=static OBJDIR=output

the directory output\release-static\(x64|x86)\bin will contain the tools
cwebp.exe and dwebp.exe. The directory output\release-static\(x64|x86)\lib will
contain the libwebp static library.
The target architecture (x86/x64) is detected by Makefile.vc from the Visual
Studio compiler (cl.exe) available in the system path.

Unix build using makefile.unix:
-------------------------------

On platforms with GNU tools installed (gcc and make), running

  make -f makefile.unix

will build the binaries examples/cwebp and examples/dwebp, along
with the static library src/libwebp.a. No system-wide installation
is supplied, as this is a simple alternative to the full installation
system based on the autoconf tools (see below).
Please refer to makefile.unix for additional details and customizations.

Using autoconf tools:
---------------------
When building from git sources, you will need to run autogen.sh to generate the
configure script.

./configure
make
make install

should be all you need to have the following files

/usr/local/include/webp/decode.h
/usr/local/include/webp/encode.h
/usr/local/include/webp/types.h
/usr/local/lib/libwebp.*
/usr/local/bin/cwebp
/usr/local/bin/dwebp

installed.

Note: A decode-only library, libwebpdecoder, is available using the
'--enable-libwebpdecoder' flag. The encode library is built separately and can
be installed independently using a minor modification in the corresponding
Makefile.am configure files (see comments there). See './configure --help' for
more options.

SWIG bindings:
--------------

To generate language bindings from swig/libwebp.swig at least swig-1.3
(http://www.swig.org) is required.

Currently the following functions are mapped:
Decode:
  WebPGetDecoderVersion
  WebPGetInfo
  WebPDecodeRGBA
  WebPDecodeARGB
  WebPDecodeBGRA
  WebPDecodeBGR
  WebPDecodeRGB

Encode:
  WebPGetEncoderVersion
  WebPEncodeRGBA
  WebPEncodeBGRA
  WebPEncodeRGB
  WebPEncodeBGR
  WebPEncodeLosslessRGBA
  WebPEncodeLosslessBGRA
  WebPEncodeLosslessRGB
  WebPEncodeLosslessBGR

See swig/README for more detailed build instructions.

Java bindings:

To build the swig-generated JNI wrapper code at least JDK-1.5 (or equivalent)
is necessary for enum support. The output is intended to be a shared object /
DLL that can be loaded via System.loadLibrary("webp_jni").

Python bindings:

To build the swig-generated Python extension code at least Python 2.6 is
required. Python < 2.6 may build with some minor changes to libwebp.swig or the
generated code, but is untested.

Encoding tool:
==============

The examples/ directory contains tools for encoding (cwebp) and
decoding (dwebp) images.

The easiest use should look like:
  cwebp input.png -q 80 -o output.webp
which will convert the input file to a WebP file using a quality factor of 80
on a 0->100 scale (0 being the lowest quality, 100 being the best. Default
value is 75).
You might want to try the -lossless flag too, which will compress the source
(in RGBA format) without any loss. The -q quality parameter will in this case
control the amount of processing time spent trying to make the output file as
small as possible.

A longer list of options is available using the -longhelp command line flag:

> cwebp -longhelp
Usage:
 cwebp [-preset <...>] [options] in_file [-o out_file]

If input size (-s) for an image is not specified, it is
assumed to be a PNG, JPEG, TIFF or WebP file.

Options:
  -h / -help  ............ short help
  -H / -longhelp  ........ long help
  -q <float> ............. quality factor (0:small..100:big)
  -alpha_q <int> ......... transparency-compression quality (0..100)
  -preset <string> ....... preset setting, one of:
                            default, photo, picture,
                            drawing, icon, text
     -preset must come first, as it overwrites other parameters
  -z <int> ............... activates lossless preset with given
                           level in [0:fast, ..., 9:slowest]

  -m <int> ............... compression method (0=fast, 6=slowest)
  -segments <int> ........ number of segments to use (1..4)
  -size <int> ............ target size (in bytes)
  -psnr <float> .......... target PSNR (in dB. typically: 42)

  -s <int> <int> ......... input size (width x height) for YUV
  -sns <int> ............. spatial noise shaping (0:off, 100:max)
  -f <int> ............... filter strength (0=off..100)
  -sharpness <int> ....... filter sharpness (0:most .. 7:least sharp)
  -strong ................ use strong filter instead of simple (default)
  -nostrong .............. use simple filter instead of strong
  -partition_limit <int> . limit quality to fit the 512k limit on
                           the first partition (0=no degradation ... 100=full)
  -pass <int> ............ analysis pass number (1..10)
  -crop <x> <y> <w> <h> .. crop picture with the given rectangle
  -resize <w> <h> ........ resize picture (after any cropping)
  -mt .................... use multi-threading if available
  -low_memory ............ reduce memory usage (slower encoding)