OPTIPNG(1)                                                          OPTIPNG(1)

NAME
       OptiPNG  -  Advanced optimization program for Portable Network Graphics
       (PNG)

SYNOPSIS
       optipng [-? | -h | -help]
       optipng [options...] files...

DESCRIPTION
       OptiPNG is a PNG optimizer that recompresses image files to  a  smaller
       size  without  losing  any information.  In addition, this program per-
       forms a suite of useful  functions  like  integrity  checks,  meta-data
       recovery and pixmap-to-PNG conversion.

FILES
       The  input  files  are  raster image files encoded either in PNG format
       (the native format), or in an external format. The currently  supported
       external formats are GIF, BMP, PNM and TIFF.

       OptiPNG processes each image file given in the command line as follows:

       - If it is in PNG format:

              Attempt to optimize the given file in-place. If optimization  is
              successful,  or  if  the option -force is in effect, replace the
              original file with its optimized version. The original  file  is
              backed up if the option -keep is in effect.

       - If it is an external format:

              Create  an  optimized  PNG version of the given file. The output
              file name is composed from the original file name and  the  .png
              extension.

OPTIONS
   Basic options
       -?, -h, -help
              Show a complete summary of options.

       -o level
              Select the optimization level.
              Use -o0 to disable IDAT recompression trials.
              Use -o1 to enable a single IDAT recompression trial.
              Use  a higher level to enable more trials (the higher the level,
              the more trials).
              The behavior and the default  value  of  this  user  option  may
              change  across  different program versions. Use option -h to see
              the details pertaining to your specific version.

       -i type
              Select the interlace type (0-1).
              Use -i0 to produce a non-interlaced output.
              Use -i1 to produce an interlaced (Adam7) output.
              If this option is not used, the output will have the same inter-
              lace type as the input.

       -k, -keep
              Keep a backup of the modified file(s).
              The  files that use the backup names prior to the program execu-
              tion are not overwritten.

       -q, -quiet
              Run in quiet mode.

       -v     Show copyright, version and build info; run in verbose mode.

   Advanced options
       -zc levels
              Select the zlib compression levels.
              The behavior and the default  value  of  this  user  option  may
              change  across  different program versions. Use option -h to see
              the details pertaining to your specific version.

       -zm levels
              Select the zlib memory levels.
              The behavior and the default  value  of  this  user  option  may
              change  across  different program versions. Use option -h to see
              the details pertaining to your specific version.

       -zs strategies
              Select the zlib compression strategies.
              The behavior and the default  value  of  this  user  option  may
              change  across  different program versions. Use option -h to see
              the details pertaining to your specific version.

       -zw window size
              Select the zlib window size (32k,16k,8k,4k,2k,1k,512,256).
              The window size can be specified either in bytes (e.g. 16384) or
              kilobytes (e.g. 16k).

       -f filters
              Select the PNG delta filters.
              The  behavior  and  the  default  value  of this user option may
              change across different program versions. The filter  values  0,
              1,  2,  3, 4 correspond to the PNG standard filters (None, Left,
              Up, Average and Paeth, respectively). The other values are  used
              to  specify adaptive filtering. Use option -h to see the details
              pertaining to your specific version.

       -nb    Do not apply bit depth reduction.

       -nc    Do not apply color type reduction.

       -np    Do not apply palette reduction.

       -nz    Do not perform IDAT recompression (also disable reductions).

       -fix   Enable error recovery.

       -force Enforce writing of a new output file.  Use this option to  over-
              ride  the  program's  decision not to write such file, e.g. when
              the PNG input is digitally signed (using dSIG), or when the  PNG
              output becomes larger than the PNG input.

       -full  Produce  a full report on IDAT.  This option might slow down the
              trials.

       -preserve
              Preserve file attributes (time stamps, file access rights, etc.)
              where applicable.

       -simulate
              Run  in  simulation  mode: perform the trials, but do not create
              output files.

       -snip  Cut one image out of multi-image, animation  or  video  file(s).
              Depending  on  the input format, this may be either the first or
              the most relevant (e.g. the largest) image.

       -out file
              Write output file to file.  The command line  must  not  contain
              more than one input file.

       -dir directory
              Write output file(s) to directory.

       -log file
              Log  messages  to  file.  For safety reasons, file must have the
              extension .log.

       --     Stop option switch parsing.

   Notes
       The option names are case-insensitive  and  can  be  abbreviated.   Any
       abbreviation must uniquely identify the full option name and must be no
       shorter than two letters, unless one letter  is  explicitly  permitted.
       For  example,  -quiet  can  be  abbreviated as -q or -qu (because -q is
       explicitly mentioned in the list of possible options), while  -preserve
       can be abbreviated as -pr but not as -p.

       Some  options  may  have arguments that follow the option name, with or
       without a whitespace used as a separator; e.g.

              -i1  <=>  -i 1
              -o3  <=>  -o 3

       Range arguments are cumulative; e.g.

              -f0 -f3-5  <=>  -f0,3-5
              -zs0 -zs1 -zs2-3  <=>  -zs0,1,2,3  <=>  -zs0-3

       The zlib window size is automatically set to a minimum  that  does  not
       affect the compression ratio.

       The  output  files  will  have  all  IDAT in a single chunk, even if no
       recompression is performed.

       Extremely exhaustive searches are not generally recommended.

EXAMPLES
       optipng file1.png file2.gif file3.tif

       optipng -o5 file1.png file2.gif file3.tif

       optipng -i1 -o7 -v -full -sim experiment.png -log experiment.log

BUGS
       Lossless image reductions are not completely implemented.   (This  does
       NOT  affect  the  integrity of the output files.)  Here are the missing
       pieces:

              - The color palette reductions are implemented only partially.
              - The bit depth reductions below 8, for  grayscale  images,  are
              not implemented yet.

       TIFF support is limited to uncompressed, PNG-compatible (grayscale, RGB
       and RGBA) images.

       Metadata is not imported from the external image formats.

SEE ALSO
       png(5), libpng(3), zlib(3), pngcrush(1), pngrewrite(1).

       Glenn Randers-Pehrson et al.  Portable Network Graphics (PNG)  Specifi-
       cation, Second Edition.
       W3C Recommendation 10 November 2003; ISO/IEC IS 15948:2003 (E).
       http://www.w3.org/TR/PNG/

AUTHOR
       OptiPNG is written and maintained by Cosmin Truta.

       This  manual  page  was originally written by Nelson A. de Oliveira for
       the Debian Project. It was later updated by Cosmin Truta,  and  is  now
       part of the OptiPNG distribution.

OptiPNG version 0.6.1            20 July 2008                       OPTIPNG(1)
