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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">
  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>2.3.┬áLayer masks</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.     <meta name="generator" content="DocBook XSL Stylesheets V1.66.1" />
  10.     <link rel="start" href="index.html" title="GIMP User Manual" />
  11.     <link rel="up" href="ch04s02.html" title="2.┬áLayers dialog" />
  12.     <link rel="prev" href="ch04s02s02.html" title="2.2.┬áUsing the Layerdialog" />
  13.     <link rel="next" href="ch04s03.html" title="3.┬áChannels dialog" />
  14.   </head>
  15.   <body>
  16.     <div xmlns="" class="navheader">
  17.       <table width="100%" summary="Navigation header">
  18.         <tr>
  19.           <th colspan="3" align="center" id="chaptername">2.┬áLayers dialog</th>
  20.         </tr>
  21.         <tr>
  22.           <td width="20%" align="left"><a accesskey="p" href="ch04s02s02.html">Prev</a>┬á</td>
  23.           <th width="60%" align="center" id="sectionname">2.3.┬áLayer masks</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>2.3.┬áLayer masks</h3>
  34.           </div>
  35.         </div>
  36.       </div>
  37.       <div class="mediaobject">
  38.         <img src="../images/dialogs/dialogs-layer-addmask.png" />
  39.       </div>
  40.       <div class="variablelist">
  41.         <dl>
  42.           <dt>
  43.             <span class="term">Overview</span>
  44.           </dt>
  45.           <dd>
  46.             <p>
  47.           A transparency mask can be added to each layer, it's called Layer
  48.           mask.  A layer mask has the same size and same pixel number as
  49.           the layer to which it is attached. Every pixel of the mask can
  50.           then be coupled with a pixel at the same location in the layer.
  51.           The mask is a set of pixels in graytone on a value scale from 0
  52.           to 255. The pixels with a value 0 are black and give a full
  53.           transparency to the coupled pixel in the layer.  The pixels with
  54.           a value 255 are white and give a full opacity to the coupled
  55.           pixel in the layer.
  56.         </p>
  57.             <p>
  58.           To create a layer mask start with a right click on the layer to
  59.           call the context menu and select <span class="guilabel">Add layer
  60.             mask</span> in the menu. If the menu item is grayed first
  61.           select <span class="guilabel">Add Alpha channel</span> in the same menu.
  62.           A dialog appears where you can initialize the content of the
  63.           mask:
  64.           </p>
  65.             <div class="itemizedlist">
  66.               <ul type="disc">
  67.                 <li>
  68.                   <p>
  69.                 <span class="guilabel">White</span>: the mask has no effect,
  70.                 all layer pixels are full visible.
  71.               </p>
  72.                 </li>
  73.                 <li>
  74.                   <p>
  75.                 <span class="guilabel">Black</span>: the mask gives a full
  76.                 transparency
  77.                 to the layer which becomes invisible.
  78.               </p>
  79.                 </li>
  80.                 <li>
  81.                   <p>
  82.                 <span class="guilabel">Layer's Alpha channel</span>: the mask is
  83.                 initialized according to the content of layer Alpha
  84.                 channel.  If the layer still contains transparency it's
  85.                 copied in the mask.
  86.               </p>
  87.                 </li>
  88.                 <li>
  89.                   <p>
  90.                 <span class="guilabel">Selection</span> : the mask is initialized
  91.                 according to pixel values found in the selection.
  92.               </p>
  93.                 </li>
  94.                 <li>
  95.                   <p>
  96.                 <span class="guilabel">Grayscale copy of layer</span>: the mask
  97.                 is
  98.                 initialized according to pixel values of the layer.
  99.               </p>
  100.                 </li>
  101.               </ul>
  102.             </div>
  103.             <p>
  104.         </p>
  105.             <p>
  106.           When the mask is created it appears as a thumbnail right to the
  107.           layer thumbnail. By clicking alternatively on the layer and mask
  108.           thumbnail you can enable one or other. The active itemis
  109.           highlighted by a white border (which is not well visible around a
  110.           white mask). To view mask content instead of its effect in image
  111.           window, press <span><b class="keycap">Ctrl Alt</b></span> and then on mask
  112.           thumbnail. To return to normal view redo last operation.
  113.         </p>
  114.             <div class="caution" style="margin-left: 0.5in; margin-right: 0.5in;">
  115.               <table border="0" summary="Caution">
  116.                 <tr>
  117.                   <td rowspan="2" align="center" valign="top" width="25">
  118.                     <img alt="[Caution]" src="../images/caution.png" />
  119.                   </td>
  120.                   <th align="left">Caution</th>
  121.                 </tr>
  122.                 <tr>
  123.                   <td colspan="2" align="left" valign="top">
  124.                     <p>
  125.             The layer mask acts like a transparency mask on a particular
  126.             layer.  Since you have many layers it becomes different from the
  127.             image Alpha channel which represents transparency applied to the
  128.             whole image.
  129.           </p>
  130.                   </td>
  131.                 </tr>
  132.               </table>
  133.             </div>
  134.           </dd>
  135.         </dl>
  136.       </div>
  137.     </div>
  138.     <div class="navfooter">
  139.       <hr />
  140.       <table width="100%" summary="Navigation footer">
  141.         <tr>
  142.           <td width="40%" align="left"><a accesskey="p" href="ch04s02s02.html">Prev</a>┬á</td>
  143.           <td width="20%" align="center">
  144.             <a accesskey="u" href="ch04s02.html">Up</a>
  145.           </td>
  146.           <td width="40%" align="right">┬á<a accesskey="n" href="ch04s03.html">Next</a></td>
  147.         </tr>
  148.         <tr>
  149.           <td width="40%" align="left" valign="top">2.2.┬áUsing the Layerdialog┬á</td>
  150.           <td width="20%" align="center">
  151.             <a accesskey="h" href="index.html">Home</a>
  152.           </td>
  153.           <td width="40%" align="right" valign="top">┬á3.┬áChannels dialog</td>
  154.         </tr>
  155.       </table>
  156.     </div>
  157.   </body>
  158. </html>
  159.