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2N/A<!--ArborText, Inc., 1988-1999, v.4002-->

2N/A<!ENTITY cmd "cjpeg">

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2N/A<!ENTITY % booktitles SYSTEM "booktitles.ent">

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2N/A<!ENTITY suncopy "Copyright (c) 2004, Sun Microsystems, Inc. All Rights Reserved.">

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2N/A<?Pub UDT _bookmark _target>

2N/A<?Pub Inc>

2N/A<refentry id="cjpeg-1">

2N/A<refmeta><refentrytitle>cjpeg</refentrytitle><manvolnum>1</manvolnum>

2N/A<refmiscinfo class="date">26 Mar 2004</refmiscinfo>

2N/A<refmiscinfo class="sectdesc">&man1;</refmiscinfo>

2N/A<refmiscinfo class="software">&release;</refmiscinfo>

2N/A<refmiscinfo class="arch">generic</refmiscinfo>

2N/A<refmiscinfo class="copyright">&suncopy;</refmiscinfo>

2N/A</refmeta>

2N/A<indexterm><primary>cjpeg</primary></indexterm><indexterm><primary>compress

2N/Aan image file to a JPEG file</primary></indexterm>

2N/A<refnamediv id="cjpeg-1-name"><refname>cjpeg</refname><refpurpose>compress

2N/Aan image file to a JPEG file</refpurpose></refnamediv>

2N/A<refsynopsisdiv id="cjpeg-1-synp"><title>&synp-tt;</title>

2N/A<cmdsynopsis><command>&cmd;</command><arg choice="opt"><option role="nodash"><replaceable>

2N/Aoptions</replaceable></option></arg><arg choice="opt"><option role="nodash"><replaceable>

2N/Afilename</replaceable></option></arg>

2N/A</cmdsynopsis></refsynopsisdiv>

2N/A<refsect1 id="cjpeg-1-desc"><title>&desc-tt;</title>

2N/A<para><command>&cmd;</command> compresses the named image file, or the standard

2N/Ainput if no file is named, and produces a JPEG/JFIF file on the standard output.

2N/AThe following input file formats are currently supported:</para>

2N/A<itemizedlist>

2N/A<listitem><para>BMP</para></listitem>

2N/A<listitem><para>PGM, the PBMPLUS gray-scale format</para></listitem>

2N/A<listitem><para>PPM, the PBMPLUS color format</para></listitem>

2N/A<listitem><para>RLE, the Utah Raster Toolkit format</para></listitem>

2N/A<listitem><para>Targa</para></listitem>

2N/A</itemizedlist>

2N/A<para>RLE is supported only if the URT library is available.</para>

2N/A</refsect1>

2N/A<refsect1 id="cjpeg-1-opts"><title>&opts-tt;</title>

2N/A<para>All options may be abbreviated. For example, <option>grayscale</option>

2N/Amay be written <option>gray</option> or <option>gr</option>. Upper and lower

2N/Acase are equivalent. For example, <option>BMP</option> is the same as <option>

2N/Abmp</option>. British spellings are also accepted. For example, <option>greyscale

2N/A</option>.</para>

2N/A<refsect2 id="cjpeg-1-opts-basic">

2N/A<title>Basic Options</title>

2N/A<para>The following basic options are supported:</para>

2N/A<variablelist termlength="medium">

2N/A<varlistentry><term><option>grayscale</option></term><listitem><para>Create

2N/Aa monochrome JPEG file from color input. You should use this switch when compressing

2N/Aa grayscale BMP file, because <command>&cmd;</command> cannot detect whether

2N/Aa BMP file uses only shades of gray. By specifying the <option>grayscale</option>

2N/Aoption, you create a smaller JPEG file that takes less time to process.</para>

2N/A</listitem></varlistentry>

2N/A<varlistentry><term><option>optimize</option></term><listitem><para>Optimize

2N/Athe entropy encoding parameters. If you do not specify this option, default

2N/Aencoding parameters are used. <option>optimize</option> usually makes the

2N/AJPEG file a little smaller, but <command>&cmd;</command> runs more slowly

2N/Aand needs much more memory. Image quality and speed of decompression are unaffected

2N/Aby the <option>optimize</option> option.</para>

2N/A</listitem></varlistentry>

2N/A<varlistentry><term><option>progressive</option></term><listitem><para>Create

2N/Aa progressive JPEG file. For more information about the <option>progressive

2N/A</option> option, see the Extended Description section.</para>

2N/A</listitem></varlistentry>

2N/A<varlistentry><term><option>quality <replaceable>N</replaceable></option></term>

2N/A<listitem><para>Scale the quantization tables to adjust image quality. <replaceable>

2N/AN</replaceable> ranges from 0 (worst) to 100 (best). The default value is

2N/A75. For more information about the <option>quality</option> option, see the

2N/AExtended Description section.</para>

2N/A</listitem></varlistentry>

2N/A<varlistentry><term><option>targa</option></term><listitem><para>Specify that

2N/Athe input file is in Targa format. Targa files that contain an "identification"

2N/Afield are not automatically recognized by <command>&cmd;</command>. For such

2N/Afiles, you must specify <option>targa</option> to make <command>&cmd;</command>

2N/Atreat the input as Targa format. For most Targa files, you do not need this

2N/Aswitch.</para>

2N/A</listitem></varlistentry>

2N/A</variablelist></refsect2>

2N/A<refsect2 id="cjpeg-1-opts-int">

2N/A<title>Intermediate Options</title>

2N/A<para>The following intermediate options are supported:</para>

2N/A<variablelist termlength="medium">

2N/A<varlistentry><term><option>dct fast</option></term><listitem><para>Use the

2N/Afast integer DCT method. This method is less accurate than the integer DCT

2N/Amethod or the floating-point DCT method.</para>

2N/A</listitem></varlistentry>

2N/A<varlistentry><term><option>dct float</option></term><listitem><para>Use the

2N/Afloating-point DCT method. The float method is very slightly more accurate

2N/Athan the int method, but is much slower unless your machine has very fast

2N/Afloating-point hardware. The results of the floating-point method may vary

2N/Aslightly across machines, while the integer methods should give the same results

2N/Aeverywhere.</para>

2N/A</listitem></varlistentry>

2N/A<varlistentry><term><option>dct int</option></term><listitem><para>Use the

2N/Ainteger DCT method. This is the default method.</para>

2N/A</listitem></varlistentry>

2N/A<varlistentry><term><option>maxmemory <replaceable>N</replaceable></option></term>

2N/A<listitem><para>Set the limit for the amount of memory to use in processing

2N/Alarge images. <replaceable>N</replaceable> is specified in thousands of bytes,

2N/Aor in millions of bytes if "M" is specified with the number. For example, <option>

2N/Amax 4m</option> selects 4000000 bytes. If more space is needed, temporary

2N/Afiles are used.</para>

2N/A</listitem></varlistentry>

2N/A<varlistentry><term><option>outfile <replaceable>name</replaceable></option></term>

2N/A<listitem><para>Send the output image to the named file, instead of to the

2N/Astandard output.</para>

2N/A</listitem></varlistentry>

2N/A<varlistentry><term><option>restart <replaceable>N</replaceable></option></term>

2N/A<listitem><para>Emit a JPEG restart marker every <replaceable>N</replaceable>

2N/AMCU rows, or every <replaceable>N</replaceable> MCU blocks if "B" is specified

2N/Awith the number. The default value is <option>restart 0</option>, which means

2N/Ano restart markers. For more information about the <option>restart</option>

2N/Aoption, see the Extended Description section.</para>

2N/A</listitem></varlistentry>

2N/A<varlistentry><term><option>smooth <replaceable>N</replaceable></option></term>

2N/A<listitem><para>Smooth the input image to eliminate dithering noise. <replaceable>

2N/AN</replaceable> ranges from 1 to 100, and indicates the strength of smoothing.

2N/AThe default value is <option>smooth 0</option>, which means no smoothing.

2N/AFor more information about the <option>smooth</option> option, see the Extended

2N/ADescription section.</para>

2N/A</listitem></varlistentry>

2N/A<varlistentry><term><option>verbose</option></term><listitem><para>Display

2N/Aversion information at startup, and enable debug printout. The <option>vv

2N/A</option> option displays more verbose output than the <option>v</option>

2N/Aoption. The <option>vvv</option> option displays the most verbose output.

2N/A</para>

2N/A<para>You can also use <option>debug</option> to specify this option.</para>

2N/A</listitem></varlistentry>

2N/A</variablelist></refsect2>

2N/A<refsect2 id="cjpeg-1-opts-adv">

2N/A<title>Advanced Options</title>

2N/A<para>The following advanced options are supported for advanced users only:

2N/A</para>

2N/A<variablelist termlength="medium">

2N/A<varlistentry><term><option>baseline</option></term><listitem><para>Force

2N/Abaseline-compatible quantization tables to be generated. This clamps the quantization

2N/Avalues to 8 bits, even at low quality settings. This option is poorly named,

2N/Abecause <option>baseline</option> does not ensure that the output is actually

2N/Abaseline JPEG. For example, you can use the <option>baseline</option> and <option>

2N/Aprogressive</option> options together.</para>

2N/A</listitem></varlistentry>

2N/A<varlistentry><term><option>qslots <replaceable>N</replaceable>[,...]</option></term>

2N/A<listitem><para>Select which quantization table to use for each color component.

2N/A</para>

2N/A</listitem></varlistentry>

2N/A<varlistentry><term><option>qtables <replaceable>file</replaceable></option></term>

2N/A<listitem><para>Use the quantization tables provided in the specified text

2N/Afile.</para>

2N/A</listitem></varlistentry>

2N/A<varlistentry><term><option>sample HxV[,...]</option></term><listitem><para>

2N/ASet the JPEG sampling factors for each color component.</para>

2N/A</listitem></varlistentry>

2N/A<varlistentry><term><option>scans <replaceable>file</replaceable></option></term>

2N/A<listitem><para>Use the scan script provided in the specified text file.</para>

2N/A</listitem></varlistentry>

2N/A</variablelist></refsect2>

2N/A</refsect1>

2N/A<refsect1 id="cjpeg-1-oper"><title>&oper-tt;</title>

2N/A<para>The following operands are supported:</para>

2N/A<variablelist termlength="medium">

2N/A<varlistentry><term><option role="nodash"><replaceable>filename</replaceable></option></term>

2N/A<listitem><para>The name of the image file to be compressed.</para>

2N/A</listitem></varlistentry>

2N/A</variablelist></refsect1>

2N/A<refsect1 id="cjpeg-1-exde"><title>&exde-tt;</title>

2N/A<refsect2 id="cjpeg-1-exde-quality">

2N/A<title>The <option>quality</option> Option</title>

2N/A<para>The <option>quality</option> option enables you to trade compressed

2N/Afile size against the quality of the reconstructed image: the higher the quality

2N/Asetting, the larger the JPEG file, and the greater the similarity between

2N/Athe output image and the original input. Normally, you use the lowest quality

2N/Asetting that decompresses into an output image that is visually indistinguishable

2N/Afrom the original image. For this purpose, the quality setting should be between

2N/A50 and 95. The default value of 75 is often just right. If you see defects

2N/Aat <option>quality 75</option>, increase the quality by 5 until you are happy

2N/Awith the output image. The optimal setting varies from one image to another.

2N/A</para>

2N/A<para>A value of <option>quality 100</option> generates a quantization table

2N/Aof ones. This minimizes loss in the quantization step, but information is

2N/Astill lost in subsampling, as well as roundoff error. The <option>quality

2N/A100</option> setting is mainly of interest for experimental purposes. Quality

2N/Avalues above 95 are not recommended for normal use, as the compressed file

2N/Asize increases dramatically for very little gain in output image quality.

2N/A</para>

2N/A<para>Quality values below 50 produce very small files of low image quality.

2N/ASettings of 5 to 10 might be useful in preparing an index of a large image

2N/Alibrary, for example. Quality values below 25 generate 2-byte quantization

2N/Atables, which are considered optional in the JPEG standard. <command>&cmd;</command>

2N/Aemits a warning message when you specify such a quality value, because some

2N/Aother JPEG programs might be unable to decode the resulting file. Use <option>

2N/Abaseline</option> if you need to ensure compatibility at low quality values.

2N/A</para>

2N/A</refsect2>

2N/A<refsect2 id="cjpeg-1-exde-prog">

2N/A<title>The <option>progressive</option> Option</title>

2N/A<para>The <option>progressive</option> option creates a "progressive JPEG"

2N/Afile. In this type of JPEG file, the data is stored in multiple scans of increasing

2N/Aquality. If the file is transmitted over a slow communications link, the decoder

2N/Acan use the first scan to display a low-quality image very quickly, and can

2N/Athen improve the display with each subsequent scan. The final image is exactly

2N/Aequivalent to a standard JPEG file of the same quality setting, and the total

2N/Afile size is about the same, or a little smaller. Caution: progressive JPEG

2N/Ais not yet widely implemented, so many decoders are unable to view a progressive

2N/AJPEG file at all.</para>

2N/A</refsect2>

2N/A<refsect2 id="cjpeg-1-exde-restart">

2N/A<title>The <option>restart</option> Option</title>

2N/A<para>The <option>restart</option> option inserts extra markers that allow

2N/Aa JPEG decoder to resynchronize after a transmission error. Without restart

2N/Amarkers, any damage to a compressed file usually ruins the image from the

2N/Apoint of the error to the end of the image. With restart markers, the damage

2N/Ais usually confined to the portion of the image from the point of the error

2N/Ato the next restart marker. The restart markers occupy extra space. We recommend <option>

2N/Arestart 1</option> for images that are transmitted across unreliable networks.

2N/A</para>

2N/A</refsect2>

2N/A<refsect2 id="cjpeg-1-exde-smooth">

2N/A<title>The <option>smooth</option> Option</title>

2N/A<para>The <option>smooth</option> option filters the input to eliminate fine-scale

2N/Anoise. This option is often useful when you convert dithered images to JPEG:

2N/Aa moderate smoothing factor of 10 to 50 deletes dithering patterns from the

2N/Ainput file, resulting in a smaller JPEG file and a better-looking image. If

2N/Athe smoothing factor is too large, the image visibly blurs.</para>

2N/A</refsect2>

2N/A<refsect2 id="cjpeg-1-exde-hints">

2N/A<title>Hints</title>

2N/A<para>Color GIF files are not the ideal input for JPEG. JPEG is really intended

2N/Afor the compression of full-color 24-bit images. In particular, do not try

2N/Ato convert cartoons, line drawings, or other images that have only a few distinct

2N/Acolors. GIF works well on these, but JPEG does not. If you want to convert

2N/Aa GIF file to JPEG, you should experiment with the <option>quality</option>

2N/Aand <option>smooth</option> options to get a satisfactory conversion. A value

2N/Aof <option>smooth 10</option> is often helpful.</para>

2N/A<para>Avoid running an image through a series of JPEG compression/decompression

2N/Acycles. Image quality loss will accumulate. After ten cycles, the image may

2N/Abe noticeably worse than it was after one cycle. Use a lossless format while

2N/Amanipulating an image, then convert to JPEG format when you are ready to file

2N/Athe image away. </para>

2N/A<para>Use the <option>optimize</option> option when you make a "final" version

2N/Afor posting or archiving. Also, when you use low quality settings, make very

2N/Asmall JPEG files. The percentage improvement is often much greater than on

2N/Alarger files. At present, the <option>optimize</option> option is always selected

2N/Awhen generating progressive JPEG files.</para>

2N/A</refsect2>

2N/A</refsect1>

2N/A<refsect1 id="cjpeg-1-exam"><title>&exam-tt;</title>

2N/A<example role="example">

2N/A<title>Compressing the PPM File test.ppm With a Quality Factor of 60 and Saving

2N/Athe Output as test.jpg</title>

2N/A<para><screen>example% <userinput>&cmd; -quality 60 test.ppm > test.jpg

2N/A</userinput></screen></para>

2N/A</example>

2N/A</refsect1>

2N/A<refsect1 id="cjpeg-1-envr"><title>&envr-tt;</title>

2N/A<para><command>&cmd;</command> uses the following environment variables:</para>

2N/A<variablelist>

2N/A<varlistentry><term>JPEGMEM</term><listitem><para>The value of this environment

2N/Avariable, if set, is the default memory limit. The value is specified as described

2N/Afor the <option>maxmemory</option> option. JPEGMEM overrides the default value

2N/Aspecified when the program was compiled, and is in turn overridden by an explicit <option>

2N/Amaxmemory</option> option.</para>

2N/A</listitem></varlistentry>

2N/A</variablelist></refsect1>

2N/A<refsect1 id="cjpeg-1-attr"><title>&attr-tt;</title>

2N/A<para>See <olink targetdocent="REFMAN5" localinfo="attributes-5"><citerefentry>

2N/A<refentrytitle>attributes</refentrytitle><manvolnum>5</manvolnum></citerefentry></olink>

2N/Afor descriptions of the following attributes:</para>

2N/A<informaltable frame="all">

2N/A<tgroup cols="2" colsep="1" rowsep="1"><colspec colname="COLSPEC0" colwidth="1*">

2N/A<colspec colname="COLSPEC1" colwidth="1*">

2N/A<thead>

2N/A<row><entry align="center" valign="middle">ATTRIBUTE TYPE</entry><entry align="center"

2N/Avalign="middle">ATTRIBUTE VALUE</entry></row>

2N/A</thead>

2N/A<tbody>

2N/A<row><entry><para>Availability</para></entry><entry><para>SUNWjpg</para></entry>

2N/A</row>

2N/A<row><entry colname="COLSPEC0"><para>Interface stability</para></entry><entry

2N/Acolname="COLSPEC1"><para>Uncommitted</para></entry></row>

2N/A</tbody>

2N/A</tgroup>

2N/A</informaltable>

2N/A</refsect1>

2N/A<refsect1 id="cjpeg-1-also"><title>&also-tt;</title>

2N/A<para>Wallace, Gregory K., <citetitle>The JPEG Still Picture Compression Standard

2N/A</citetitle> Communications of the ACM, April 1991 (vol. 34, no. 4), pp. 30-44.

2N/A</para>

2N/A<para><citerefentry><refentrytitle>djpeg</refentrytitle><manvolnum>1</manvolnum>

2N/A</citerefentry>, <citerefentry><refentrytitle>jpegtran</refentrytitle><manvolnum>

2N/A1</manvolnum></citerefentry>, <citerefentry><refentrytitle>rdjpgcom</refentrytitle>

2N/A<manvolnum>1</manvolnum></citerefentry>, <citerefentry><refentrytitle>wrjpgcom

2N/A</refentrytitle><manvolnum>1</manvolnum></citerefentry></para>

2N/A</refsect1>

2N/A<refsect1 id="cjpeg-1-note"><title>&note-tt;</title>

2N/A<para>Arithmetic coding is not supported. GIF input files are not supported.

2N/ANot all variants of BMP and Targa file formats are supported.</para>

2N/A<para>This man page was originally written by the Independent JPEG Group.

2N/AUpdated by Breda McColgan, Sun Microsystems Inc., 2004. </para>

2N/A</refsect1>

2N/A</refentry>

2N/A