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  1. <?xml version="1.0" encoding="UTF-8" standalone="no"?>
  2. <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
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  4.   <head>
  5.     <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
  6.     <title>9.6.¬† Indexed mode</title>
  7.     <link rel="stylesheet" href="gimp-help-plain.css" type="text/css" />
  8.     <link rel="stylesheet" href="gimp-help-screen.css" type="text/css" />
  9.     <link rel="stylesheet" href="gimp-help-custom.css" type="text/css" />
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  12.     <link rel="start" href="index.html" title="GNU Image Manipulation Program" />
  13.     <link rel="up" href="gimp-imagewindow-menus-image.html" title="9.¬† The ‚ÄúImage‚Äù Menu" />
  14.     <link rel="prev" href="gimp-image-convert-grayscale.html" title="9.5.¬† Grayscale mode" />
  15.     <link rel="next" href="gimp-image-transform.html" title="9.7.¬† Transform" />
  16.   </head>
  17.   <body>
  18.     <div class="navheader">
  19.       <table width="100%" summary="Navigation header">
  20.         <tr>
  21.           <th colspan="3" align="center">9.6.¬†
  22.     <span lang="en" xml:lang="en">Indexed mode</span>
  23.   </th>
  24.         </tr>
  25.         <tr>
  26.           <td width="20%" align="left"><a accesskey="p" href="gimp-image-convert-grayscale.html"><img src="../images/prev.png" alt="Prev" /></a>¬†</td>
  27.           <th width="60%" align="center">9.¬†
  28.     <span lang="en" xml:lang="en">The ‚Äú<span class="quote">Image</span>‚Äù Menu</span>
  29.   </th>
  30.           <td width="20%" align="right">¬†<a accesskey="n" href="gimp-image-transform.html"><img src="../images/next.png" alt="Next" /></a></td>
  31.         </tr>
  32.       </table>
  33.       <hr />
  34.     </div>
  35.     <div class="sect2" lang="en" xml:lang="en">
  36.       <div class="titlepage">
  37.         <div>
  38.           <div>
  39.             <h3 class="title"><a id="gimp-image-convert-indexed"></a>9.6.¬†
  40.     <span lang="en" xml:lang="en">Indexed mode</span>
  41.   </h3>
  42.           </div>
  43.           <div>
  44.             <div class="revhistory">
  45.               <table border="1" width="100%" summary="Revision history">
  46.                 <tr>
  47.                   <th align="left" valign="top" colspan="3">
  48.                     <b>Revision History</b>
  49.                   </th>
  50.                 </tr>
  51.                 <tr>
  52.                   <td align="left">Revision $Revision: 2336 $</td>
  53.                   <td align="left">2006-08-01</td>
  54.                   <td align="left">scb</td>
  55.                 </tr>
  56.               </table>
  57.             </div>
  58.           </div>
  59.         </div>
  60.       </div>
  61.       <a id="id2696611" class="indexterm"></a>
  62.       <a id="id2696628" class="indexterm"></a>
  63.       <a id="id2696643" class="indexterm"></a>
  64.       <p>
  65.     The <span class="guimenuitem">Indexed</span> command converts your image to
  66.     indexed mode. See
  67.     <a class="link" href="glossary.html#glossary-colormodel" title="Color model">indexed colors</a> in the
  68.     Glossary for more information about Indexed Color Mode.
  69.   </p>
  70.       <div class="sect3" lang="en" xml:lang="en">
  71.         <div class="titlepage">
  72.           <div>
  73.             <div>
  74.               <h4 class="title"><a id="id2696672"></a>9.6.1.¬†
  75.       <span lang="en" xml:lang="en">Activating the Command</span>
  76.     </h4>
  77.             </div>
  78.           </div>
  79.         </div>
  80.         <div class="itemizedlist">
  81.           <ul type="disc">
  82.             <li>
  83.               <p>
  84.           You can access this command from the image menubar through
  85.           <span class="guimenu"><span class="accel">I</span>mage</span> ‚Üí <span class="guisubmenu"><span class="accel">M</span>ode</span> ‚Üí <span class="guimenuitem"><span class="accel">I</span>ndexed</span>.
  86.         </p>
  87.             </li>
  88.           </ul>
  89.         </div>
  90.       </div>
  91.       <div class="sect3" lang="en" xml:lang="en">
  92.         <div class="titlepage">
  93.           <div>
  94.             <div>
  95.               <h4 class="title"><a id="id2696729"></a>9.6.2.¬†
  96.       <span lang="en" xml:lang="en">
  97.         The ‚Äú<span class="quote">Convert Image to Indexed Colors</span>‚Äù dialog
  98.       </span>
  99.     </h4>
  100.             </div>
  101.           </div>
  102.         </div>
  103.         <p>
  104.       The <span class="guimenuitem">Indexed</span> command opens the
  105.       <span class="guilabel">Convert Image to Indexed Colors</span> dialog.
  106.     </p>
  107.         <div class="figure">
  108.           <a id="id2696761"></a>
  109.           <p class="title">
  110.             <b>Figure¬†15.66.¬†
  111.         <span lang="en" xml:lang="en">
  112.           The ‚Äú<span class="quote">Convert Image to Indexed Colors</span>‚Äù dialog
  113.         </span>
  114.       </b>
  115.           </p>
  116.           <div class="figure-contents">
  117.             <div class="mediaobject">
  118.               <img src="../images/dialogs/dialogs-image-mode-indexed.png" alt="The Convert Image to Indexed Colors dialog" />
  119.             </div>
  120.           </div>
  121.         </div>
  122.         <br class="figure-break" />
  123.         <div class="variablelist">
  124.           <dl>
  125.             <dt>
  126.               <span class="term">Colormap Options</span>
  127.             </dt>
  128.             <dd>
  129.               <div class="itemizedlist">
  130.                 <ul type="disc">
  131.                   <li>
  132.                     <p>
  133.                 <span class="guilabel">Generate optimum palette</span>:
  134.                 This option generates the best possible palette with a
  135.                 default maximum number of 256 colors (classic GIF format).
  136.                 You can reduce this
  137.                 <span class="emphasis"><em>Maximum Number of Colors</em></span>, although
  138.                 this may create unwanted effects (color banding) on smooth
  139.                 transitions. You may be able to lessen the unwanted effects
  140.                 by using dithering, however.
  141.               </p>
  142.                   </li>
  143.                   <li>
  144.                     <p>
  145.                 <span class="guilabel">Use web-optimized palette</span>: use a
  146.                 palette that is optimized for the web.
  147.               </p>
  148.                   </li>
  149.                   <li>
  150.                     <p>
  151.                 <span class="guilabel">Use black and white (1-bit) palette</span>:
  152.                 This option generates an image which uses only two colors,
  153.                 black and white.
  154.               </p>
  155.                   </li>
  156.                   <li>
  157.                     <p>
  158.                 <span class="guilabel">Use custom palette</span>:
  159.                 This button lets you select a custom palette from a list.
  160.                 The number of colors is indicated for each palette. The
  161.                 ‚Äú<span class="quote">Web</span>‚Äù palette, with 216 colors, is the
  162.                 ‚Äú<span class="quote">web-safe</span>‚Äù palette. It was originally created
  163.                 by Netscape to
  164.                 provide colors that would look the same on both Macs and
  165.                 PCs, and Internet Explorer 3 could manage it. Since
  166.                 version 4, MSIE handles a 212 color palette. The problem
  167.                 of color similarity between all platforms has not been
  168.                 solved yet and it probably never will be. When designing a
  169.                 web page, you should keep two principles in mind: use light
  170.                 text on a dark background or dark text on a light
  171.                 background, and never rely on color to convey information.
  172.               </p>
  173.                     <p>
  174.                 Some colors in the palette may not be used if your image
  175.                 does not have many colors. They will be removed from the
  176.                 palette if the <span class="guilabel">Remove unused colors from final
  177.                 palette</span> option is checked.
  178.               </p>
  179.                   </li>
  180.                 </ul>
  181.               </div>
  182.             </dd>
  183.             <dt>
  184.               <span class="term">Dithering Options</span>
  185.             </dt>
  186.             <dd>
  187.               <p>
  188.             Since an indexed image contains 256 colors or less, some colors
  189.             in the original image may not be available in the palette. This
  190.             may result in some blotchy or solid patches in areas which
  191.             should have subtle color changes. The dithering options let you
  192.             correct the unwanted effects created by the Palette Options.
  193.           </p>
  194.               <p>
  195.             A dithering filter tries to approximate a color which is
  196.             missing from the palette by instead using clusters of pixels
  197.             of similar colors which are in the palette. When seen from a
  198.             distance, these pixels give the impression of a new color. See
  199.             the Glossary for more information on
  200.             <a class="link" href="glossary.html#glossary-dithering" title="Dithering">dithering</a>.
  201.           </p>
  202.               <p>
  203.             Three filters (plus ‚Äú<span class="quote">None</span>‚Äù) are available. It is
  204.             not possible to predict what the result of a particular filter
  205.             will be on your image, so you will have to try all of them and
  206.             see which works best. The
  207.             ‚Äú<span class="quote">Positioned Color Dithering</span>‚Äù filter is well
  208.             adapted to animations.
  209.           </p>
  210.               <div class="figure">
  211.                 <a id="id2696982"></a>
  212.                 <p class="title">
  213.                   <b>Figure¬†15.67.¬†
  214.               <span lang="en" xml:lang="en">
  215.                 Example: full color, with no dithering
  216.               </span>
  217.             </b>
  218.                 </p>
  219.                 <div class="figure-contents">
  220.                   <div class="mediaobject">
  221.                     <img src="../images/dialogs/examples/dither1.png" alt="Example: full color, with no dithering" />
  222.                     <div class="caption">
  223.                       <p>
  224.                   This is an example image with a smooth transition in
  225.                   RGB Mode.
  226.                 </p>
  227.                     </div>
  228.                   </div>
  229.                 </div>
  230.               </div>
  231.               <br class="figure-break" />
  232.               <div class="figure">
  233.                 <a id="id2697021"></a>
  234.                 <p class="title">
  235.                   <b>Figure¬†15.68.¬†
  236.               <span lang="en" xml:lang="en">
  237.                 Example: four colors, with no dithering
  238.               </span>
  239.             </b>
  240.                 </p>
  241.                 <div class="figure-contents">
  242.                   <div class="mediaobject">
  243.                     <img src="../images/dialogs/examples/dither2.png" alt="Example: four colors, with no dithering" />
  244.                     <div class="caption">
  245.                       <p>
  246.                   The same image, after being transformed to four indexed
  247.                   colors, without dithering.
  248.                 </p>
  249.                     </div>
  250.                   </div>
  251.                 </div>
  252.               </div>
  253.               <br class="figure-break" />
  254.               <div class="figure">
  255.                 <a id="id2697060"></a>
  256.                 <p class="title">
  257.                   <b>Figure¬†15.69.¬†
  258.               <span lang="en" xml:lang="en">
  259.                 Example: Floyd-Steinberg (normal)
  260.               </span>
  261.             </b>
  262.                 </p>
  263.                 <div class="figure-contents">
  264.                   <div class="mediaobject">
  265.                     <img src="../images/dialogs/examples/dither3.png" alt="Example: Floyd-Steinberg (normal)" />
  266.                     <div class="caption">
  267.                       <p>
  268.                   The same image, with four indexed colors and
  269.                   ‚Äú<span class="quote">Floyd-Steinberg (normal)</span>‚Äù dithering.
  270.                 </p>
  271.                     </div>
  272.                   </div>
  273.                 </div>
  274.               </div>
  275.               <br class="figure-break" />
  276.               <div class="figure">
  277.                 <a id="id2697102"></a>
  278.                 <p class="title">
  279.                   <b>Figure¬†15.70.¬†
  280.               <span lang="en" xml:lang="en">
  281.                 Example: Floyd-Steinberg (reduced color bleeding)
  282.               </span>
  283.             </b>
  284.                 </p>
  285.                 <div class="figure-contents">
  286.                   <div class="mediaobject">
  287.                     <img src="../images/dialogs/examples/dither4.png" alt="Example: Floyd-Steinberg (reduced color bleeding)" />
  288.                     <div class="caption">
  289.                       <p>
  290.                   The same image, with four indexed colors and
  291.                   ‚Äú<span class="quote">Floyd-Steinberg (reduced color bleeding)</span>‚Äù
  292.                   dithering.
  293.                 </p>
  294.                     </div>
  295.                   </div>
  296.                 </div>
  297.               </div>
  298.               <br class="figure-break" />
  299.               <p>
  300.             In a GIF image, transparency is encoded in 1 bit: transparent
  301.             or not transparent. To give the illusion of partial
  302.             transparency, you can use the <span class="guilabel">Enable dithering of
  303.               transparency</span> option. However, the
  304.             <a class="link" href="plug-in-semiflatten.html" title="14.3.¬† Semi-Flatten">Semi-flatten</a>
  305.             plug-in may give you better results.
  306.           </p>
  307.             </dd>
  308.           </dl>
  309.         </div>
  310.         <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
  311.           <table border="0" summary="Note">
  312.             <tr>
  313.               <td rowspan="2" align="center" valign="top" width="25">
  314.                 <img alt="[Note]" src="../images/note.png" />
  315.               </td>
  316.               <th align="left">Note</th>
  317.             </tr>
  318.             <tr>
  319.               <td align="left" valign="top">
  320.                 <p>
  321.         You can edit the color palette of an indexed image by using the
  322.         <a class="link" href="gimp-indexed-palette-dialog.html" title="2.4.¬† Colormap Dialog">Colormap Dialog</a>.
  323.       </p>
  324.               </td>
  325.             </tr>
  326.           </table>
  327.         </div>
  328.       </div>
  329.     </div>
  330.     <div class="navfooter">
  331.       <hr />
  332.       <table width="100%" summary="Navigation footer">
  333.         <tr>
  334.           <td width="40%" align="left"><a accesskey="p" href="gimp-image-convert-grayscale.html"><img src="../images/prev.png" alt="Prev" /></a>¬†</td>
  335.           <td width="20%" align="center">
  336.             <a accesskey="u" href="gimp-imagewindow-menus-image.html">
  337.               <img src="../images/up.png" alt="Up" />
  338.             </a>
  339.           </td>
  340.           <td width="40%" align="right">¬†<a accesskey="n" href="gimp-image-transform.html"><img src="../images/next.png" alt="Next" /></a></td>
  341.         </tr>
  342.         <tr>
  343.           <td width="40%" align="left" valign="top"><a accesskey="p" href="gimp-image-convert-grayscale.html">9.5.¬†
  344.     <span lang="en" xml:lang="en">Grayscale mode</span>
  345.   </a>¬†</td>
  346.           <td width="20%" align="center">
  347.             <a accesskey="h" href="index.html">
  348.               <img src="../images/home.png" alt="Home" />
  349.             </a>
  350.           </td>
  351.           <td width="40%" align="right" valign="top">¬†<a accesskey="n" href="gimp-image-transform.html">9.7.¬†
  352.     <span lang="en" xml:lang="en">Transform</span>
  353.   </a></td>
  354.         </tr>
  355.       </table>
  356.     </div>
  357.   </body>
  358. </html>
  359.