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  2. <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
  3. <html xmlns="http://www.w3.org/1999/xhtml">
  4.   <head>
  5.     <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
  6.     <title>2.2.┬áLayer masks</title>
  7.     <link rel="stylesheet" href="gimp-help-plain.css" type="text/css" />
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  10.     <link rel="home" href="index.html" title="GIMP User Manual" />
  11.     <link rel="up" href="ch04s02.html" title="2.┬áLayers dialog" />
  12.     <link rel="previous" href="ch04s02.html" title="2.┬áLayers dialog" />
  13.     <link rel="next" href="ch04s03.html" title="3.┬áChannels dialog" />
  14.   </head>
  15.   <body>
  16.     <div class="navheader">
  17.       <table width="100%" summary="Navigation header">
  18.         <tr>
  19.           <th colspan="3" align="center">2.2.┬áLayer masks</th>
  20.         </tr>
  21.         <tr>
  22.           <td width="20%" align="left"><a accesskey="p" href="ch04s02.html">Prev</a>┬á</td>
  23.           <th width="60%" align="center">2.┬áLayers dialog</th>
  24.           <td width="20%" align="right">┬á<a accesskey="n" href="ch04s03.html">Next</a></td>
  25.         </tr>
  26.       </table>
  27.       <hr />
  28.     </div>
  29.     <div class="sect2" lang="en" xml:lang="en">
  30.       <div class="titlepage">
  31.         <div>
  32.           <div>
  33.             <h3 class="title"><a id="gimp-layer-mask"></a>2.2.┬áLayer masks</h3>
  34.           </div>
  35.         </div>
  36.         <div></div>
  37.       </div>
  38.       <div class="mediaobject">
  39.         <img src="../images/dialogs/dialogs-layer-addmask.png" />
  40.       </div>
  41.       <div class="variablelist">
  42.         <dl>
  43.           <dt></dt>
  44.           <dd>
  45.             <p>
  46.           A transparency mask can be added to each layer, it's called Layer
  47.           mask.  A layer mask has the same size and same pixel number as
  48.           the layer to which it is attached. Every pixel of the mask can
  49.           then be coupled with a pixel at the same location in the layer.
  50.           The mask is a set of pixels in graytone on a value scale from 0
  51.           to 255. The pixels with a value 0 are black and give a full
  52.           transparency to the coupled pixel in the layer.  The pixels with
  53.           a value 255 are white and give a full opacity to the coupled
  54.           pixel in the layer.
  55.         </p>
  56.             <p>
  57.           To create a layer mask start with a right click on the layer to
  58.           call the context menu and select <span class="guilabel">Add layer
  59.             mask</span> in the menu. If the menu item is grayed first
  60.           select <span class="guilabel">Add Alpha channel</span> in the same menu.
  61.           A dialog appears where you can initialize the content of the
  62.           mask:
  63.           </p>
  64.             <div class="itemizedlist">
  65.               <ul type="disc">
  66.                 <li>
  67.                   <p>
  68.                 <span class="guilabel">White</span>: the mask has no effect,
  69.                 all layer pixels are full visible.
  70.               </p>
  71.                 </li>
  72.                 <li>
  73.                   <p>
  74.                 <span class="guilabel">Black</span>: the mask gives a full
  75.                 transparency
  76.                 to the layer which becomes invisible.
  77.               </p>
  78.                 </li>
  79.                 <li>
  80.                   <p>
  81.                 <span class="guilabel">Layer's Alpha channel</span>: the mask is
  82.                 initialized according to the content of layer Alpha
  83.                 channel.  If the layer still contains transparency it's
  84.                 copied in the mask.
  85.               </p>
  86.                 </li>
  87.                 <li>
  88.                   <p>
  89.                 <span class="guilabel">Selection</span> : the mask is initialized
  90.                 according to pixel values found in the selection.
  91.               </p>
  92.                 </li>
  93.                 <li>
  94.                   <p>
  95.                 <span class="guilabel">Grayscale copy of layer</span>: the mask
  96.                 is
  97.                 initialized according to pixel values of the layer.
  98.               </p>
  99.                 </li>
  100.               </ul>
  101.             </div>
  102.             <p>
  103.         </p>
  104.             <p>
  105.           When the mask is created it appears as a thumbnail right to the
  106.           layer thumbnail. By clicking alternatively on the layer and mask
  107.           thumbnail you can enable one or other. The active itemis
  108.           highlighted by a white border (which is not well visible around a
  109.           white mask). To view mask content instead of its effect in image
  110.           window, press <span><b class="keycap">Ctrl Alt</b></span> and then on mask
  111.           thumbnail. To return to normal view redo last operation.
  112.         </p>
  113.             <div class="caution" style="margin-left: 0.5in; margin-right: 0.5in;">
  114.               <table border="0" summary="Caution">
  115.                 <tr>
  116.                   <td rowspan="2" align="center" valign="top" width="25">
  117.                     <img alt="[Caution]" src="../images/caution.png" />
  118.                   </td>
  119.                   <th align="left">Caution</th>
  120.                 </tr>
  121.                 <tr>
  122.                   <td colspan="2" align="left" valign="top">
  123.           The layer mask acts like a transparency mask on a particular
  124.           layer.  Since you have many layers it becomes different from the
  125.           image Alpha channel which represents transparency applied to the
  126.           whole image.
  127.         </td>
  128.                 </tr>
  129.               </table>
  130.             </div>
  131.           </dd>
  132.         </dl>
  133.       </div>
  134.     </div>
  135.     <div class="navfooter">
  136.       <hr />
  137.       <table width="100%" summary="Navigation footer">
  138.         <tr>
  139.           <td width="40%" align="left"><a accesskey="p" href="ch04s02.html">Prev</a>┬á</td>
  140.           <td width="20%" align="center">
  141.             <a accesskey="u" href="ch04s02.html">Up</a>
  142.           </td>
  143.           <td width="40%" align="right">┬á<a accesskey="n" href="ch04s03.html">Next</a></td>
  144.         </tr>
  145.         <tr>
  146.           <td width="40%" align="left" valign="top">2.┬áLayers dialog┬á</td>
  147.           <td width="20%" align="center">
  148.             <a accesskey="h" href="index.html">Home</a>
  149.           </td>
  150.           <td width="40%" align="right" valign="top">┬á3.┬áChannels dialog</td>
  151.         </tr>
  152.       </table>
  153.     </div>
  154.   </body>
  155. </html>
  156.