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| <title>OPTIPNG</title> |
| |
| </head> |
| <body> |
| |
| <h1 align="center">OPTIPNG</h1> |
| |
| <hr> |
| |
| |
| <h2>NAME |
| <a name="NAME"></a> |
| </h2> |
| |
| |
| <p style="margin-left:11%; margin-top: 1em"><b>OptiPNG</b> |
| − Optimize Portable Network Graphics files</p> |
| |
| <h2>SYNOPSIS |
| <a name="SYNOPSIS"></a> |
| </h2> |
| |
| |
| <p style="margin-left:11%; margin-top: 1em"><b>optipng</b> |
| [<b>−?</b> | <b>−h</b> | <b>−help</b>] |
| <b><br> |
| optipng</b> [<i>options...</i>] <i>files...</i></p> |
| |
| <h2>DESCRIPTION |
| <a name="DESCRIPTION"></a> |
| </h2> |
| |
| |
| <p style="margin-left:11%; margin-top: 1em">The |
| <b>OptiPNG</b> program shall attempt to <i>optimize</i> PNG |
| files, i.e. reduce their size to a minimum, without losing |
| semantic information. In addition, this program shall |
| perform a suite of auxiliary functions like integrity |
| checks, metadata recovery and pixmap-to-PNG conversion.</p> |
| |
| <p style="margin-left:11%; margin-top: 1em">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.</p> |
| |
| <h2>FILES |
| <a name="FILES"></a> |
| </h2> |
| |
| |
| <p style="margin-left:11%; margin-top: 1em">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.</p> |
| |
| <p style="margin-left:11%; margin-top: 1em"><b>OptiPNG</b> |
| processes each image file given in the command line as |
| follows:</p> |
| |
| <p style="margin-left:11%; margin-top: 1em">− If the |
| image is in PNG format:</p> |
| |
| <p style="margin-left:22%; margin-top: 1em">Attempts to |
| optimize the given file in-place. If optimization is |
| successful, or if the option <b>−force</b> is enabled, |
| replaces the original file with its optimized version. The |
| original file is backed up if the option <b>−keep</b> |
| is enabled.</p> |
| |
| <p style="margin-left:11%; margin-top: 1em">− If the |
| image is in an external format:</p> |
| |
| <p style="margin-left:22%; margin-top: 1em">Creates an |
| optimized PNG version of the given file. The output file |
| name is composed from the original file name and the |
| <tt>.png</tt> extension.</p> |
| |
| <p style="margin-left:11%; margin-top: 1em">Existing files |
| are <i>not</i> overwritten, unless the option |
| <b>−clobber</b> is enabled.</p> |
| |
| <h2>OPTIONS |
| <a name="OPTIONS"></a> |
| </h2> |
| |
| |
| <p style="margin-left:11%; margin-top: 1em"><b>General |
| options <br> |
| −?</b>, <b>−h</b>, <b>−help</b></p> |
| |
| <p style="margin-left:22%;">Show a complete summary of |
| options.</p> |
| |
| <p style="margin-left:11%;"><b>−backup</b>, |
| <b>−keep</b></p> |
| |
| <p style="margin-left:22%;">Keep a backup of the modified |
| files.</p> |
| |
| <p style="margin-left:11%;"><b>−clobber</b></p> |
| |
| <p style="margin-left:22%;">Overwrite the existing output |
| and backup files. <br> |
| Under this option, if the option <b>−backup</b> is not |
| enabled, the old backups of the overwritten files are |
| deleted.</p> |
| |
| <p style="margin-left:11%;"><b>−dir</b> |
| <i>directory</i></p> |
| |
| <p style="margin-left:22%;">Write the output files to |
| <i>directory</i>.</p> |
| |
| <table width="100%" border="0" rules="none" frame="void" |
| cellspacing="0" cellpadding="0"> |
| <tr valign="top" align="left"> |
| <td width="11%"></td> |
| <td width="6%"> |
| |
| |
| <p><b>−fix</b></p></td> |
| <td width="5%"></td> |
| <td width="78%"> |
| |
| |
| <p>Enable error recovery. This option has no effect on |
| valid input files.</p></td></tr> |
| </table> |
| |
| <p style="margin-left:22%;">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. <br> |
| When this option is not used, the invalid input files are |
| left unprocessed.</p> |
| |
| <table width="100%" border="0" rules="none" frame="void" |
| cellspacing="0" cellpadding="0"> |
| <tr valign="top" align="left"> |
| <td width="11%"></td> |
| <td width="9%"> |
| |
| |
| <p style="margin-top: 1em"><b>−force</b></p></td> |
| <td width="2%"></td> |
| <td width="56%"> |
| |
| |
| <p style="margin-top: 1em">Enforce writing of a new output |
| file.</p> </td> |
| <td width="22%"> |
| </td></tr> |
| </table> |
| |
| <p style="margin-left:22%;">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.</p> |
| |
| <p style="margin-left:11%;"><b>−log</b> |
| <i>file</i></p> |
| |
| <p style="margin-left:22%;">Log messages to <i>file</i>. |
| For safety reasons, <i>file</i> must have the extension |
| <tt>.log</tt>. <br> |
| This option is deprecated and will be removed eventually. |
| Use shell redirection.</p> |
| |
| <p style="margin-left:11%;"><b>−out</b> |
| <i>file</i></p> |
| |
| <p style="margin-left:22%;">Write output file to |
| <i>file</i>. The command line must contain exactly one input |
| file.</p> |
| |
| <p style="margin-left:11%;"><b>−preserve</b></p> |
| |
| <p style="margin-left:22%;">Preserve file attributes (time |
| stamps, file access rights, etc.) where applicable.</p> |
| |
| <p style="margin-left:11%;"><b>−quiet</b>, |
| <b>−silent</b></p> |
| |
| <p style="margin-left:22%;">Run in quiet mode. <br> |
| The messages are still written to the log file if the option |
| <b>−log</b> is enabled.</p> |
| |
| <p style="margin-left:11%;"><b>−simulate</b></p> |
| |
| <p style="margin-left:22%;">Run in simulation mode: perform |
| the trials, but do not create output files.</p> |
| |
| <table width="100%" border="0" rules="none" frame="void" |
| cellspacing="0" cellpadding="0"> |
| <tr valign="top" align="left"> |
| <td width="11%"></td> |
| <td width="3%"> |
| |
| |
| <p><b>−v</b></p></td> |
| <td width="8%"></td> |
| <td width="63%"> |
| |
| |
| <p>Enable the options <b>−verbose</b> and |
| <b>−version</b>.</p> </td> |
| <td width="15%"> |
| </td></tr> |
| </table> |
| |
| <p style="margin-left:11%;"><b>−verbose</b></p> |
| |
| <p style="margin-left:22%;">Run in verbose mode.</p> |
| |
| <p style="margin-left:11%;"><b>−version</b></p> |
| |
| <p style="margin-left:22%;">Show copyright, version and |
| build info.</p> |
| |
| <table width="100%" border="0" rules="none" frame="void" |
| cellspacing="0" cellpadding="0"> |
| <tr valign="top" align="left"> |
| <td width="11%"></td> |
| <td width="3%"> |
| |
| |
| <p><b>−−</b></p></td> |
| <td width="8%"></td> |
| <td width="41%"> |
| |
| |
| <p>Stop option switch parsing.</p></td> |
| <td width="37%"> |
| </td></tr> |
| </table> |
| |
| <p style="margin-left:11%; margin-top: 1em"><b>PNG encoding |
| and optimization options <br> |
| −o</b> <i>level</i></p> |
| |
| <p style="margin-left:22%;">Select the optimization level. |
| <br> |
| 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. <br> |
| The optimization level 1 enables a single IDAT compression |
| trial. The trial chosen is what <b>OptiPNG</b> <i>thinks</i> |
| it’s probably the most effective. <br> |
| The optimization levels 2 and higher enable multiple IDAT |
| compression trials; the higher the level, the more trials. |
| <br> |
| The behavior and the default value of this option may change |
| across different program versions. Use the option |
| <b>−h</b> to see the details pertaining to your |
| specific version.</p> |
| |
| <p style="margin-left:11%;"><b>−f</b> |
| <i>filters</i></p> |
| |
| <p style="margin-left:22%;">Select the PNG delta filters. |
| <br> |
| The <i>filters</i> argument is specified as a rangeset (e.g. |
| <b>−f0−5</b>), and the default <i>filters</i> |
| value depends on the optimization level set by the option |
| <b>−o</b>. <br> |
| The filter values 0, 1, 2, 3 and 4 indicate static |
| filtering, and correspond to the standard PNG filter codes |
| (<i>None</i>, <i>Left</i>, <i>Up</i>, <i>Average</i> and |
| <i>Paeth</i>, respectively). The filter value 5 indicates |
| adaptive filtering, whose effect is defined by the |
| <b>libpng</b>(3) library used by <b>OptiPNG</b>.</p> |
| |
| <table width="100%" border="0" rules="none" frame="void" |
| cellspacing="0" cellpadding="0"> |
| <tr valign="top" align="left"> |
| <td width="11%"></td> |
| <td width="7%"> |
| |
| |
| <p><b>−full</b></p></td> |
| <td width="4%"></td> |
| <td width="78%"> |
| |
| |
| <p>Produce a full report on IDAT. This option might slow |
| down the trials.</p></td></tr> |
| </table> |
| |
| <p style="margin-left:11%;"><b>−i</b> <i>type</i></p> |
| |
| <p style="margin-left:22%;">Select the interlace type |
| (0−1). <br> |
| 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 <i>Adam7</i> method. <br> |
| By default, the output shall have the same interlace type as |
| the input.</p> |
| |
| <table width="100%" border="0" rules="none" frame="void" |
| cellspacing="0" cellpadding="0"> |
| <tr valign="top" align="left"> |
| <td width="11%"></td> |
| <td width="4%"> |
| |
| |
| <p><b>−nb</b></p></td> |
| <td width="7%"></td> |
| <td width="78%"> |
| |
| |
| <p>Do not apply bit depth reduction.</p></td></tr> |
| <tr valign="top" align="left"> |
| <td width="11%"></td> |
| <td width="4%"> |
| |
| |
| <p><b>−nc</b></p></td> |
| <td width="7%"></td> |
| <td width="78%"> |
| |
| |
| <p>Do not apply color type reduction.</p></td></tr> |
| <tr valign="top" align="left"> |
| <td width="11%"></td> |
| <td width="4%"> |
| |
| |
| <p><b>−np</b></p></td> |
| <td width="7%"></td> |
| <td width="78%"> |
| |
| |
| <p>Do not apply palette reduction.</p></td></tr> |
| <tr valign="top" align="left"> |
| <td width="11%"></td> |
| <td width="4%"> |
| |
| |
| <p><b>−nx</b></p></td> |
| <td width="7%"></td> |
| <td width="78%"> |
| |
| |
| <p>Do not apply any lossless image reduction: enable the |
| options <b>−nb</b>, <b>−nc</b> and |
| <b>−np</b>.</p> </td></tr> |
| <tr valign="top" align="left"> |
| <td width="11%"></td> |
| <td width="4%"> |
| |
| |
| <p><b>−nz</b></p></td> |
| <td width="7%"></td> |
| <td width="78%"> |
| |
| |
| <p>Do not recode IDAT datastreams.</p></td></tr> |
| </table> |
| |
| <p style="margin-left:22%;">The IDAT optimization |
| operations that do not require recoding (e.g. IDAT chunk |
| concatenation) are still performed. <br> |
| This option has effect on PNG input files only.</p> |
| |
| <p style="margin-left:11%;"><b>−zc</b> |
| <i>levels</i></p> |
| |
| <p style="margin-left:22%;">Select the zlib compression |
| levels used in IDAT compression. <br> |
| The <i>levels</i> argument is specified as a rangeset (e.g. |
| <b>−zc6−9</b>), and the default <i>levels</i> |
| value depends on the optimization level set by the option |
| <b>−o</b>. <br> |
| The effect of this option is defined by the <b>zlib</b>(3) |
| library used by <b>OptiPNG</b>.</p> |
| |
| <p style="margin-left:11%;"><b>−zm</b> |
| <i>levels</i></p> |
| |
| <p style="margin-left:22%;">Select the zlib memory levels |
| used in IDAT compression. <br> |
| The <i>levels</i> argument is specified as a rangeset (e.g. |
| <b>−zm8−9</b>), and the default <i>levels</i> |
| value depends on the optimization level set by the option |
| <b>−o</b>. <br> |
| The effect of this option is defined by the <b>zlib</b>(3) |
| library used by <b>OptiPNG</b>.</p> |
| |
| <p style="margin-left:11%;"><b>−zs</b> |
| <i>strategies</i></p> |
| |
| <p style="margin-left:22%;">Select the zlib compression |
| strategies used in IDAT compression. <br> |
| The <i>strategies</i> argument is specified as a rangeset |
| (e.g. <b>−zs0−3</b>), and the default |
| <i>strategies</i> value depends on the optimization level |
| set by the option <b>−o</b>. <br> |
| The effect of this option is defined by the <b>zlib</b>(3) |
| library used by <b>OptiPNG</b>.</p> |
| |
| <p style="margin-left:11%;"><b>−zw</b> |
| <i>size</i></p> |
| |
| <p style="margin-left:22%;">Select the zlib window size |
| (32k,16k,8k,4k,2k,1k,512,256) used in IDAT compression. <br> |
| The <i>size</i> argument can be specified either in bytes |
| (e.g. 16384) or kilobytes (e.g. 16k). The default |
| <i>size</i> value is set to the lowest window size that |
| yields an IDAT output as big as if yielded by the value |
| 32768. <br> |
| The effect of this option is defined by the <b>zlib</b>(3) |
| library used by <b>OptiPNG</b>.</p> |
| |
| <p style="margin-left:11%; margin-top: 1em"><b>Editing |
| options</b></p> |
| |
| <table width="100%" border="0" rules="none" frame="void" |
| cellspacing="0" cellpadding="0"> |
| <tr valign="top" align="left"> |
| <td width="11%"></td> |
| <td width="7%"> |
| |
| |
| <p><b>−snip</b></p></td> |
| <td width="4%"></td> |
| <td width="78%"> |
| |
| |
| <p>Cut one image out of multi-image, animation or video |
| files.</p> </td></tr> |
| </table> |
| |
| <p style="margin-left:22%;">Depending on the input format, |
| this may be either the first or the most relevant (e.g. the |
| largest) image.</p> |
| |
| <p style="margin-left:11%;"><b>−strip</b> |
| <i>objects</i></p> |
| |
| <p style="margin-left:22%;">Strip metadata objects from a |
| PNG file. <br> |
| PNG metadata is the information stored in any ancillary |
| chunk except tRNS. (tRNS represents the alpha channel, |
| which, even if ignored in rendering, is still a proper image |
| channel in the RGBA color space.) <br> |
| The only option currently supported is <b>−strip |
| all</b>.</p> |
| |
| <p style="margin-left:11%; margin-top: 1em"><b>Notes</b> |
| <br> |
| Options may come in any order (except for |
| <b>−−</b>), before, after, or alternating with |
| file names. Option names are case-insensitive and may be |
| abbreviated to their shortest unique prefix.</p> |
| |
| <p style="margin-left:11%; margin-top: 1em">Some options |
| may have arguments that follow the option name, separated by |
| whitespace or the equal sign (’<b>=</b>’). If |
| the option argument is a number or a rangeset, the separator |
| may be omitted. For example:</p> |
| |
| |
| <p style="margin-left:22%; margin-top: 1em"><b>−out</b> |
| <tt>newfile.png </tt><=> |
| <b>−out=</b><tt>newfile.png</tt> <b><br> |
| −o3 </b><=> <b>−o 3 |
| </b><=> <b>−o=3 <br> |
| −f0,3−5 </b><=> <b>−f |
| 0,3−5 </b><=> |
| <b>−f=0,3−5</b></p> |
| |
| <p style="margin-left:11%; margin-top: 1em">Rangeset |
| arguments are cumulative; e.g.</p> |
| |
| <p style="margin-left:22%; margin-top: 1em"><b>−f0 |
| −f3−5 </b><=> |
| <b>−f0,3−5 <br> |
| −zs0 −zs1 −zs2−3 </b><=> |
| <b>−zs0,1,2,3 </b><=> |
| <b>−zs0−3</b></p> |
| |
| <h2>EXTENDED DESCRIPTION |
| <a name="EXTENDED DESCRIPTION"></a> |
| </h2> |
| |
| |
| <p style="margin-left:11%; margin-top: 1em">The PNG |
| optimization algorithm consists of the following steps:</p> |
| |
| <table width="100%" border="0" rules="none" frame="void" |
| cellspacing="0" cellpadding="0"> |
| <tr valign="top" align="left"> |
| <td width="11%"></td> |
| <td width="3%"> |
| |
| |
| <p>1.</p></td> |
| <td width="3%"></td> |
| <td width="83%"> |
| |
| |
| <p>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).</p> </td></tr> |
| <tr valign="top" align="left"> |
| <td width="11%"></td> |
| <td width="3%"> |
| |
| |
| <p>2.</p></td> |
| <td width="3%"></td> |
| <td width="83%"> |
| |
| |
| <p>Run a suite of compression methods and strategies and |
| select the compression parameters that yield the smallest |
| output file.</p></td></tr> |
| <tr valign="top" align="left"> |
| <td width="11%"></td> |
| <td width="3%"> |
| |
| |
| <p>3.</p></td> |
| <td width="3%"></td> |
| <td width="83%"> |
| |
| |
| <p>Store all IDAT contents into a single chunk, eliminating |
| the overhead incurred by repeated IDAT headers and CRCs.</p></td></tr> |
| <tr valign="top" align="left"> |
| <td width="11%"></td> |
| <td width="3%"> |
| |
| |
| <p>4.</p></td> |
| <td width="3%"></td> |
| <td width="83%"> |
| |
| |
| <p>Set the zlib window size inside IDAT to a mininum that |
| does not affect the compression ratio, reducing the memory |
| requirements of PNG decoders.</p></td></tr> |
| </table> |
| |
| <p style="margin-left:11%; margin-top: 1em">Not all of the |
| above steps need to be executed. The behavior depends on the |
| actual input files and user options.</p> |
| |
| <p style="margin-left:11%; margin-top: 1em">Step 1 may be |
| customized via the no-reduce options <b>−nb</b>, |
| <b>−nc</b>, <b>−np</b> and <b>−nx</b>. |
| Step 2 may be customized via the <b>−o</b> option, and |
| may be fine-tuned via the options <b>−zc</b>, |
| <b>−zm</b>, <b>−zs</b> and <b>−zw</b>. |
| 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 |
| <b>−zw</b>.</p> |
| |
| <p style="margin-left:11%; margin-top: 1em">Extremely |
| exhaustive searches are not generally expected to yield |
| significant improvements in compression ratio, and are |
| recommended to advanced users only.</p> |
| |
| <h2>EXAMPLES |
| <a name="EXAMPLES"></a> |
| </h2> |
| |
| |
| <p style="margin-left:11%; margin-top: 1em"><tt>optipng |
| file.png </tt># default speed |
| <tt><br> |
| optipng -o5 file.png </tt># slow <tt><br> |
| optipng -o7 file.png </tt># very slow</p> |
| |
| <h2>BUGS |
| <a name="BUGS"></a> |
| </h2> |
| |
| |
| <p style="margin-left:11%; margin-top: 1em">Lossless image |
| reductions are not completely implemented. (This does |
| <i>not</i> affect the integrity of the output files.) Here |
| are the missing pieces:</p> |
| |
| <p style="margin-left:22%; margin-top: 1em">− The |
| color palette reductions are implemented only partially. |
| <br> |
| − The bit depth reductions below 8, for grayscale |
| images, are not implemented yet.</p> |
| |
| <p style="margin-left:11%; margin-top: 1em">Encoding of |
| images whose total IDAT size exceeds 2GB is not |
| supported.</p> |
| |
| <p style="margin-left:11%; margin-top: 1em">TIFF support is |
| limited to uncompressed, PNG-compatible (grayscale, RGB and |
| RGBA) images.</p> |
| |
| <p style="margin-left:11%; margin-top: 1em">Metadata is not |
| imported from the external image formats.</p> |
| |
| <p style="margin-left:11%; margin-top: 1em">There is no |
| support for pipes or streams.</p> |
| |
| <h2>SEE ALSO |
| <a name="SEE ALSO"></a> |
| </h2> |
| |
| |
| <p style="margin-left:11%; margin-top: 1em"><b>png</b>(5), |
| <b>libpng</b>(3), <b>zlib</b>(3), <b>pngcrush</b>(1), |
| <b>pngrewrite</b>(1).</p> |
| |
| <h2>STANDARDS |
| <a name="STANDARDS"></a> |
| </h2> |
| |
| |
| <p style="margin-left:11%; margin-top: 1em">The files |
| produced by <b>OptiPNG</b> are compliant with |
| <b>PNG−2003</b>: <br> |
| Glenn Randers-Pehrson et al. <i>Portable Network Graphics |
| (PNG) Specification, Second Edition</i>. <br> |
| W3C Recommendation 10 November 2003; ISO/IEC IS 15948:2003 |
| (E). <tt><br> |
| http://www.w3.org/TR/PNG/</tt></p> |
| |
| <h2>AUTHOR |
| <a name="AUTHOR"></a> |
| </h2> |
| |
| |
| |
| <p style="margin-left:11%; margin-top: 1em"><tt><b>OptiPNG</b></tt> |
| is written and maintained by Cosmin Truta.</p> |
| |
| <p style="margin-left:11%; margin-top: 1em">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 <b>OptiPNG</b> distribution.</p> |
| <hr> |
| </body> |
| </html> |
