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  4.   <head>
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  6.     <title>11.8.¬† White Balance</title>
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  14.     <link rel="prev" href="gimp-layer-equalize.html" title="11.7.¬† Equalize" />
  15.     <link rel="next" href="plug-in-color-enhance.html" title="11.9.¬† Color Enhance" />
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  18.     <div class="navheader">
  19.       <table width="100%" summary="Navigation header">
  20.         <tr>
  21.           <th colspan="3" align="center">11.8.¬†
  22.     <span lang="en" xml:lang="en">White Balance</span>
  23.   </th>
  24.         </tr>
  25.         <tr>
  26.           <td width="20%" align="left"><a accesskey="p" href="gimp-layer-equalize.html"><img src="../images/prev.png" alt="Prev" /></a>¬†</td>
  27.           <th width="60%" align="center">11.¬†
  28.     <span lang="en" xml:lang="en">The ‚Äú<span class="quote">Colors</span>‚Äù Menu</span>
  29.   </th>
  30.           <td width="20%" align="right">¬†<a accesskey="n" href="plug-in-color-enhance.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-layer-white-balance"></a>11.8.¬†
  40.     <span lang="en" xml:lang="en">White Balance</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: 2419 $</td>
  53.                   <td align="left">2007-10-17</td>
  54.                   <td align="left">ude</td>
  55.                 </tr>
  56.               </table>
  57.             </div>
  58.           </div>
  59.         </div>
  60.       </div>
  61.       <a id="id2717473" class="indexterm"></a>
  62.       <a id="id2717488" class="indexterm"></a>
  63.       <p>
  64.     The <span class="guimenuitem">White Balance</span> command automatically
  65.     adjusts the colors of the active layer by stretching the Red, Green and
  66.     Blue channels separately. To do this, it discards pixel colors at each
  67.     end of the Red, Green and Blue histograms which are used by only 0.05%
  68.     of the pixels in the image and stretches the remaining range as much as
  69.     possible. The result is that pixel colors which occur very infrequently
  70.     at the outer edges of the histograms (perhaps bits of dust, etc.) do
  71.     not negatively influence the minimum and maximum values used for
  72.     stretching the histograms, in comparison with <a class="link" href="plug-in-c-astretch.html" title="11.11.¬† Stretch Contrast">Stretch Contrast</a>.  Like
  73.     ‚Äú<span class="quote">Stretch Contrast</span>‚Äù, however, there may be hue shifts in
  74.     the resulting image.
  75.   </p>
  76.       <p> 
  77.     This command suits images with poor white or black. Since it tends to
  78.     create pure white (and black), it may be useful e.g. to enhance
  79.     photographs.
  80.   </p>
  81.       <p>
  82.     <span class="guimenuitem">White Balance</span> operates on layers from RGB
  83.     images. If the image is Indexed or Grayscale, the menu item is insensitive
  84.     and grayed out.
  85.   </p>
  86.       <div class="sect3" lang="en" xml:lang="en">
  87.         <div class="titlepage">
  88.           <div>
  89.             <div>
  90.               <h4 class="title"><a id="id2717553"></a>11.8.1.¬†
  91.       <span lang="en" xml:lang="en">Activate Command</span>
  92.     </h4>
  93.             </div>
  94.           </div>
  95.         </div>
  96.         <div class="itemizedlist">
  97.           <ul type="disc">
  98.             <li>
  99.               <p>
  100.           You can access this command from the image menubar through
  101.           <span class="guimenu"><span class="accel">C</span>olors</span> ‚Üí <span class="guisubmenu"><span class="accel">A</span>uto</span> ‚Üí <span class="guimenuitem"><span class="accel">W</span>hite¬†Balance</span>.
  102.         </p>
  103.             </li>
  104.           </ul>
  105.         </div>
  106.       </div>
  107.       <div class="sect3" lang="en" xml:lang="en">
  108.         <div class="titlepage">
  109.           <div>
  110.             <div>
  111.               <h4 class="title"><a id="id2717608"></a>11.8.2.¬†
  112.       <span lang="en" xml:lang="en">
  113.         ‚Äú<span class="quote">White Balance</span>‚Äù example
  114.       </span>
  115.     </h4>
  116.             </div>
  117.           </div>
  118.         </div>
  119.         <div class="figure">
  120.           <a id="id2717622"></a>
  121.           <p class="title">
  122.             <b>Figure¬†15.139.¬†
  123.         <span lang="en" xml:lang="en">Original image</span>
  124.       </b>
  125.           </p>
  126.           <div class="figure-contents">
  127.             <div class="mediaobject">
  128.               <img src="../images/menus/alice.png" alt="Original image" />
  129.               <div class="caption">
  130.                 <p>
  131.             The active layer and its Red, Green and Blue histograms
  132.             before ‚Äú<span class="quote">White Balance</span>‚Äù.
  133.           </p>
  134.               </div>
  135.             </div>
  136.           </div>
  137.         </div>
  138.         <br class="figure-break" />
  139.         <div class="figure">
  140.           <a id="id2717663"></a>
  141.           <p class="title">
  142.             <b>Figure¬†15.140.¬†
  143.         <span lang="en" xml:lang="en">Image after the command</span>
  144.       </b>
  145.           </p>
  146.           <div class="figure-contents">
  147.             <div class="mediaobject">
  148.               <img src="../images/menus/white-balance.png" alt="Image after the command" />
  149.               <div class="caption">
  150.                 <p>
  151.             The active layer and its Red, Green and Blue histograms after
  152.             ‚Äú<span class="quote">White Balance</span>‚Äù.  Poor white areas in the image
  153.             became pure white.
  154.           </p>
  155.                 <p>
  156.             Histogram stretching creates gaps between the pixel columns,
  157.             giving it a striped look.
  158.           </p>
  159.               </div>
  160.             </div>
  161.           </div>
  162.         </div>
  163.         <br class="figure-break" />
  164.       </div>
  165.     </div>
  166.     <div class="navfooter">
  167.       <hr />
  168.       <table width="100%" summary="Navigation footer">
  169.         <tr>
  170.           <td width="40%" align="left"><a accesskey="p" href="gimp-layer-equalize.html"><img src="../images/prev.png" alt="Prev" /></a>¬†</td>
  171.           <td width="20%" align="center">
  172.             <a accesskey="u" href="gimp-imagewindow-menus-colors.html">
  173.               <img src="../images/up.png" alt="Up" />
  174.             </a>
  175.           </td>
  176.           <td width="40%" align="right">¬†<a accesskey="n" href="plug-in-color-enhance.html"><img src="../images/next.png" alt="Next" /></a></td>
  177.         </tr>
  178.         <tr>
  179.           <td width="40%" align="left" valign="top"><a accesskey="p" href="gimp-layer-equalize.html">11.7.¬†
  180.     <span lang="en" xml:lang="en">Equalize</span>
  181.   </a>¬†</td>
  182.           <td width="20%" align="center">
  183.             <a accesskey="h" href="index.html">
  184.               <img src="../images/home.png" alt="Home" />
  185.             </a>
  186.           </td>
  187.           <td width="40%" align="right" valign="top">¬†<a accesskey="n" href="plug-in-color-enhance.html">11.9.¬†
  188.     <span lang="en" xml:lang="en">Color Enhance</span>
  189.   </a></td>
  190.         </tr>
  191.       </table>
  192.     </div>
  193.   </body>
  194. </html>
  195.