Provided by: optipng_0.6.4-1_i386 bug

NAME

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

SYNOPSIS

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

DESCRIPTION

       The OptiPNG program shall attempt to optimize PNG  files,  i.e.  reduce
       their  size  to a minimum, without losing any information. In addition,
       this  program  shall  perform  a  suite  of  auxiliary  functions  like
       integrity checks, metadata recovery and pixmap-to-PNG conversion.

       The  optimization  attempts  are  not  guaranteed to succeed. Valid PNG
       files that cannot be  optimized  by  this  program  are  normally  left
       intact; their size will not grow. The user may request to override this
       default behavior.

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 in 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

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

       -o level
              Select the optimization level.
              The   optimization   level  0  enables  a  set  of  optimization
              operations that require minimal effort. There will be no changes
              to  image  attributes  like  bit  depth  or  color  type, and no
              recompression of existing IDAT datastreams.
              The optimization level  1  enables  a  single  IDAT  compression
              trial. The trial chosen is what OptiPNG thinks it's probably the
              most effective.
              The optimization  levels  2  and  higher  enable  multiple  IDAT
              compression trials; the higher the level, the more trials.
              The  behavior  and  the  default value of this option may change
              across different program versions. Use the option -h to see  the
              details pertaining to your specific version.

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

       -fix   Enable  error recovery. This option has no effect on valid input
              files.
              The program will spend a reasonable amount of effort to  recover
              as  much  data  as  possible, without increasing the output file
              size, but  the  success  cannot  be  generally  guaranteed.  The
              program may even increase the file size, e.g., by reconstructing
              missing critical data. Under this option, integrity  shall  take
              precedence over file size.
              When  this  option is not used, the invalid input files are left
              unprocessed.

       -force Enforce writing of a new output file.
              This option overrides 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.

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

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

       -out file
              Write output file  to  file.   The  command  line  must  contain
              exactly one input file.

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

       -quiet Run in quiet mode.
              These messages are still written to the log file if  the  option
              -log is in effect.

       -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.

       -v     Enable the options -verbose and -version.

       -verbose
              Run in verbose mode.

       -version
              Show copyright, version and build info.

       --     Stop option switch parsing.

   PNG encoding and optimization options
       -f filters
              Select the PNG delta filters.
              The  filters  argument  is specified as a rangeset (e.g. -f0-5),
              and the default filters value depends on the optimization  level
              set by the option -o.
              The  filter  values  0, 1, 2, 3 and 4 indicate static filtering,
              and correspond to the standard PNG filter codes (None, Left, Up,
              Average  and  Paeth, respectively). The filter value 5 indicates
              adaptive filtering, whose effect is  defined  by  the  libpng(3)
              library used by OptiPNG.

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

       -i type
              Select the interlace type (0-1).
              If the interlace type 0 is selected, the output image  shall  be
              non-interlaced (i.e. progressive-scanned). If the interlace type
              1 is selected, the output image shall be  interlaced  using  the
              Adam7 method.
              By default, the output shall have the same interlace type as the
              input.

       -nb    Do not apply bit depth reduction.

       -nc    Do not apply color type reduction.

       -np    Do not apply palette reduction.

       -nx    Do not apply any lossless image reduction:  enable  the  options
              -nb, -nc and -np.

       -nz    Do not recode IDAT datastreams.
              The  IDAT  optimization  operations that do not require recoding
              (e.g. IDAT chunk concatenation) are still performed.
              This option has effect on PNG input files only.

       -zc levels
              Select the zlib compression levels used in IDAT compression.
              The levels argument is specified as a  rangeset  (e.g.  -zc6-9),
              and  the  default levels value depends on the optimization level
              set by the option -o.
              The effect of this option is defined by the zlib(3) library used
              by OptiPNG.

       -zm levels
              Select the zlib memory levels used in IDAT compression.
              The  levels  argument  is specified as a rangeset (e.g. -zm8-9),
              and the default levels value depends on the  optimization  level
              set by the option -o.
              The effect of this option is defined by the zlib(3) library used
              by OptiPNG.

       -zs strategies
              Select the zlib compression strategies used in IDAT compression.
              The  strategies  argument  is  specified  as  a  rangeset  (e.g.
              -zs0-3),  and  the  default  strategies  value  depends  on  the
              optimization level set by the option -o.
              The effect of this option is defined by the zlib(3) library used
              by OptiPNG.

       -zw size
              Select  the  zlib window size (32k,16k,8k,4k,2k,1k,512,256) used
              in IDAT compression.
              The size argument can be specified either in bytes (e.g.  16384)
              or  kilobytes  (e.g.  16k). The default size value is set to the
              lowest window size that yields an  IDAT  output  as  big  as  if
              yielded by the value 32768.
              The effect of this option is defined by the zlib(3) library used
              by OptiPNG.

   Notes
       Options may come in any  order  (except  for  --),  before,  after,  or
       alternating  with file names. Option names are case-insensitive and may
       be abbreviated to their shortest unique prefix.

       Some options may have arguments that follow the option name,  separated
       by  whitespace  or  the  equal  sign ('='). If the option argument is a
       number or a rangeset, the separator may be omitted. For example:

              -out newfile.png  <=>  -out=newfile.png
              -o3  <=>  -o 3  <=>  -o=3
              -f0,3-5  <=>  -f 0,3-5  <=>  -f=0,3-5

       Rangeset arguments are cumulative; e.g.

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

EXTENDED DESCRIPTION

       The PNG optimization algorithm consists of the following steps:

       1.  Reduce the bit depth, the color type and the color palette  of  the
           image.   This  step  may reduce the size of the uncompressed image,
           which, indirectly, may reduce the  size  of  the  compressed  image
           (i.e. the size of the output PNG file).

       2.  Run  a  suite  of compression methods and strategies and select the
           compression parameters that yield the smallest output file.

       3.  Store all IDAT  contents  into  a  single  chunk,  eliminating  the
           overhead incurred by repeated IDAT headers and CRCs.

       4.  Set  the  zlib  window  size inside IDAT to a mininum that does not
           affect the compression ratio, reducing the memory  requirements  of
           PNG decoders.

       Not all of the above steps need to be executed. The behavior depends on
       the actual input files and user options.

       Step 1 may be customized via the no-reduce options -nb,  -nc,  -np  and
       -nx.  Step 2 may be customized via the -o option, and may be fine-tuned
       via the options -zc, -zm, -zs and -zw. Step 3 is always executed.  Step
       4  is  executed  only  if a new IDAT is being created, and may be fine-
       tuned via the option -zw.

       Extremely exhaustive searches  are  not  generally  expected  to  yield
       significant  improvements  in compression ratio, and are recommended to
       advanced users only.

EXAMPLES

       optipng file1.png file2.gif file3.tif

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

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

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.

       There is no support for pipes or streams.

SEE ALSO

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

STANDARDS

       The files produced by OptiPNG are compliant with PNG-2003:
       Glenn  Randers-Pehrson  et  al.   Portable   Network   Graphics   (PNG)
       Specification, 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.