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  1. <?xml version="1.0" encoding="UTF-8" standalone="no"?>
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  4.   <head>
  5.     <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
  6.     <title>3.9.┬áConvolve (Blur/Sharpen)</title>
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  11.     <link rel="up" href="ch03s03.html" title="3.┬áBrush Tools" />
  12.     <link rel="prev" href="ch03s03s08.html" title="3.8.┬áClone Tool" />
  13.     <link rel="next" href="ch03s03s10.html" title="3.10.┬áDodge or Burn" />
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  15.   <body>
  16.     <div xmlns="" class="navheader">
  17.       <table width="100%" summary="Navigation header">
  18.         <tr>
  19.           <th colspan="3" align="center" id="chaptername">3.┬áBrush Tools</th>
  20.         </tr>
  21.         <tr>
  22.           <td width="20%" align="left"><a accesskey="p" href="ch03s03s08.html">Prev</a>┬á</td>
  23.           <th width="60%" align="center" id="sectionname">3.9.┬áConvolve (Blur/Sharpen)</th>
  24.           <td width="20%" align="right">┬á<a accesskey="n" href="ch03s03s10.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-tool-convolve"></a>3.9.┬áConvolve (Blur/Sharpen)</h3>
  34.           </div>
  35.         </div>
  36.       </div>
  37.       <a id="id3439090" class="indexterm"></a>
  38.       <div class="informalfigure">
  39.         <div class="mediaobject">
  40.           <img src="../images/toolbox/toolbox-blur.png" />
  41.           <div class="caption">
  42.             <p>
  43.           Convolve tool icon in the Toolbox
  44.         </p>
  45.           </div>
  46.         </div>
  47.       </div>
  48.       <p>
  49.     The Convolve tool uses the current brush to locally blur or
  50.     sharpen your image. Blurring with it can be useful if some element
  51.     of your image stands out too much, and you would like to soften
  52.     it.  If you want to blur a whole layer, or a large part of one,
  53.     you will probably be better off using one of the <a href="ch06s02.html" title="2.┬áBlur filters">Blur Filters</a>.  The direction of a
  54.     brushstroke has no effect:  if you want directional blurring, use
  55.     the Smudge tool.
  56.   </p>
  57.       <p>
  58.     In "Sharpen" mode, the tool works by increasing the contrast where
  59.     the brush is applied.  A little bit of this may be useful, but
  60.     overapplication will produce noise.  Some of the <a href="ch06s06.html" title="6.┬áEnhance filters">Enhancement Filters</a>, particularly
  61.     the <a href="ch06s06s07.html" title="6.7.┬áUnsharp Mask">Unsharp Mask</a>, do a
  62.     much cleaner job of sharpening areas of a layer.
  63.   </p>
  64.       <div class="tip" style="margin-left: 0.5in; margin-right: 0.5in;">
  65.         <table border="0" summary="Tip">
  66.           <tr>
  67.             <td rowspan="2" align="center" valign="top" width="25">
  68.               <img alt="[Tip]" src="../images/tip.png" />
  69.             </td>
  70.             <th align="left">Tip</th>
  71.           </tr>
  72.           <tr>
  73.             <td colspan="2" align="left" valign="top">
  74.               <p>
  75.       You can create a more sophisticated sharpening brush using the
  76.       Clone tool.  To do this, start by duplicating the layer you want
  77.       to work on, and run a sharpening filter, such as Unsharp Mask,
  78.       on the copy.  Then activate the Clone tool, and in its Tool
  79.       Options set Source to "Image source" and Alignment to
  80.       "Registered".  Set the Opacity to a modest value, such as 10.
  81.       Then Ctrl-click on the copy to make it the source image.  If you
  82.       now paint on the original layer, you will mix together, where
  83.       the brush is applied, the sharpened version with the unsharpened
  84.       version. 
  85.     </p>
  86.             </td>
  87.           </tr>
  88.         </table>
  89.       </div>
  90.       <p>
  91.     Both blurring and sharpening work incrementally:  moving the brush
  92.     repeatedly over an area will increase the effect with each
  93.     additional pass.  The Rate control allows you to determine how
  94.     quickly the modifications accumulate.  The Opacity control,
  95.     however, can be used to limit the amount of blurring that can be
  96.     produced by a single brushstroke, regardless of how many passes
  97.     are made with it.
  98.   </p>
  99.       <div class="simplesect" lang="en" xml:lang="en">
  100.         <div class="titlepage">
  101.           <div>
  102.             <div>
  103.               <h4 class="title"><a id="id3439199"></a>How to Activate</h4>
  104.             </div>
  105.           </div>
  106.         </div>
  107.         <p>
  108.       The Convolve tool can be activated from an image menu as
  109.       <span class="guimenu">Tools</span>-><span class="guisubmenu">Paint Tools</span>-><span class="guimenuitem">Convolve</span>; 
  110.       from the Toolbox by clicking on the tool icon 
  111.       <span class="guiicon">
  112.         <span class="inlinemediaobject"><img src="../images/toolbox/blur.png" /></span>
  113.       </span>;
  114.       or from the keyboard using the shortcut <span><b class="keycap">V</b></span>.
  115.     </p>
  116.       </div>
  117.       <div class="simplesect" lang="en" xml:lang="en">
  118.         <div class="titlepage">
  119.           <div>
  120.             <div>
  121.               <h4 class="title"><a id="id3439255"></a>Key modifiers</h4>
  122.             </div>
  123.           </div>
  124.         </div>
  125.         <p>
  126.       See the <a href="ch03s03.html#gimp-tool-brush" title="3.1.┬áCommon Features">Brush Tools
  127.       Overview</a> for a description of key modifiers that have the
  128.       same effect on all brush tools.
  129.     </p>
  130.         <div class="itemizedlist">
  131.           <ul type="disc">
  132.             <li>
  133.               <p>
  134.           <span><b class="keycap">Ctrl</b></span>:
  135.           Holding down the Ctrl key toggles between Blur and Sharpen
  136.           modes; it reverses the setting shown in the Tool Options. 
  137.         </p>
  138.             </li>
  139.           </ul>
  140.         </div>
  141.       </div>
  142.       <div class="simplesect" lang="en" xml:lang="en">
  143.         <div class="titlepage">
  144.           <div>
  145.             <div>
  146.               <h4 class="title"><a id="id3439293"></a>Tool Options</h4>
  147.             </div>
  148.           </div>
  149.         </div>
  150.         <div class="informalfigure">
  151.           <div class="mediaobject">
  152.             <img src="../images/toolbox/tool-options-convolve.png" />
  153.             <div class="caption">
  154.               <p>
  155.             Tool Options for the Convolve tool
  156.           </p>
  157.             </div>
  158.           </div>
  159.         </div>
  160.         <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
  161.           <table border="0" summary="Note">
  162.             <tr>
  163.               <td rowspan="2" align="center" valign="top" width="25">
  164.                 <img alt="[Note]" src="../images/note.png" />
  165.               </td>
  166.               <th align="left">Note</th>
  167.             </tr>
  168.             <tr>
  169.               <td colspan="2" align="left" valign="top">
  170.                 <p>
  171.         See the <a href="ch03s03.html#gimp-tool-brush" title="3.1.┬áCommon Features">Brush Tools
  172.         Overview</a> for a description of tool options that apply to
  173.         many or all brush tools.
  174.       </p>
  175.               </td>
  176.             </tr>
  177.           </table>
  178.         </div>
  179.         <div class="variablelist">
  180.           <dl>
  181.             <dt>
  182.               <span class="term">Convolve Type</span>
  183.             </dt>
  184.             <dd>
  185.               <p>
  186.           <span class="emphasis"><em>Blur</em></span> mode causes each pixel affected by
  187.           the brush to be blended with neighboring pixels, thereby increasing the
  188.           similarity of pixels inside the brushstroke area.
  189.           <span class="emphasis"><em>Sharpen</em></span> mode causes each pixel to
  190.           become more different from its neighbors than it previously
  191.           was:  it increases contrast inside the brushstroke area.
  192.           Whatever setting you choose here, you can reverse it
  193.           on-the-fly by holding down the Ctrl key.
  194.         </p>
  195.             </dd>
  196.             <dt>
  197.               <span class="term">Rate</span>
  198.             </dt>
  199.             <dd>
  200.               <p>
  201.           The <span class="guilabel">Rate</span> slider sets the strength of the
  202.           convolve effect.
  203.         </p>
  204.             </dd>
  205.           </dl>
  206.         </div>
  207.       </div>
  208.     </div>
  209.     <div class="navfooter">
  210.       <hr />
  211.       <table width="100%" summary="Navigation footer">
  212.         <tr>
  213.           <td width="40%" align="left"><a accesskey="p" href="ch03s03s08.html">Prev</a>┬á</td>
  214.           <td width="20%" align="center">
  215.             <a accesskey="u" href="ch03s03.html">Up</a>
  216.           </td>
  217.           <td width="40%" align="right">┬á<a accesskey="n" href="ch03s03s10.html">Next</a></td>
  218.         </tr>
  219.         <tr>
  220.           <td width="40%" align="left" valign="top">3.8.┬áClone Tool┬á</td>
  221.           <td width="20%" align="center">
  222.             <a accesskey="h" href="index.html">Home</a>
  223.           </td>
  224.           <td width="40%" align="right" valign="top">┬á3.10.┬áDodge or Burn</td>
  225.         </tr>
  226.       </table>
  227.     </div>
  228.   </body>
  229. </html>
  230.