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  • Committer: Bazaar Package Importer
  • Author(s): Ari Pollak
  • Date: 2005-05-08 18:04:08 UTC
  • mfrom: (1.2.1 upstream) (2.1.1 hoary)
  • Revision ID: james.westby@ubuntu.com-20050508180408-mjwl3kmjczfnmu5v
Tags: 2+0.7-5
http://bugs.debian.org/308228
Fix doc-base entry for gimp-help-zh-cn to point to correct directory
name (Closes: #308228)

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html/en/ch05s10s11.html
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<?xml version="1.0" encoding="UTF-8" standalone="no"?>
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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
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<html xmlns="http://www.w3.org/1999/xhtml">
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  <head>
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    <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
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    <title>10.11. Newsprint</title>
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    <link rel="stylesheet" href="gimp-help-plain.css" type="text/css" />
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    <link rel="stylesheet" href="gimp-help-screen.css" type="text/css" />
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    <meta name="generator" content="DocBook XSL Stylesheets V1.64.1" />
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    <link rel="home" href="index.html" title="GIMP User Manual" />
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    <link rel="up" href="ch05s10.html" title="10. Distort filters" />
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    <link rel="previous" href="ch05s10s10.html" title="10.10. Shift" />
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    <link rel="next" href="ch05s10s12.html" title="10.12. Video" />
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  </head>
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  <body>
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    <div class="navheader">
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      <table width="100%" summary="Navigation header">
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        <tr>
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          <th colspan="3" align="center">10.11. Newsprint</th>
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        </tr>
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        <tr>
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          <td width="20%" align="left"><a accesskey="p" href="ch05s10s10.html">Prev</a> </td>
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          <th width="60%" align="center">10. Distort filters</th>
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          <td width="20%" align="right"> <a accesskey="n" href="ch05s10s12.html">Next</a></td>
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        </tr>
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      </table>
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      <hr />
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    </div>
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    <div class="sect2" lang="en" xml:lang="en">
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      <div class="titlepage">
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        <div>
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          <div>
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            <h3 class="title"><a id="plug-in-newsprint"></a>10.11. Newsprint</h3>
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          </div>
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        </div>
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        <div></div>
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      </div>
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      <a id="id2981170" class="indexterm"></a>
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      <div class="mediaobject">
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        <img src="../images/filters/filters-distort-newsprint.png" />
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      </div>
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      <div class="simplesect" lang="en" xml:lang="en">
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        <div class="titlepage">
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          <div>
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            <div>
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              <h4 class="title"><a id="id2981192"></a>Overview</h4>
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            </div>
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          </div>
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          <div></div>
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        </div>
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        <div class="variablelist">
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          <dl>
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            <dt></dt>
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            <dd>
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              <p>
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            This filter is found in
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            <span class="guimenuitem">Image&gt;Filters/Distorts/Newsprin<span class="accel">t</span></span>
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          </p>
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              <p>
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            This filter halftones the image using a clustered-dot
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            dither.  Halftoning is the process of rendering an image with 
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            multiple levels of grey or colour (i.e. a continuous tone image) 
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            on a device with fewer tones; often a bi-level device such as a 
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            printer or typesetter.
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          </p>
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              <p>
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            The basic premise is to trade off resolution for greater 
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            apparent tone depth (this is known as spatial dithering).
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          </p>
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              <p> 
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            There are many approaches to this, the simplest of which is to 
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            throw away the low-order bits of tone information; this is what 
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            the posterize filter does. Unfortunately, the results don't look 
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            too good. However, no spatial resolution is lost.
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          </p>
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              <p>
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            This filter uses a clustered-dot ordered dither, which reduces 
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            the resolution of the image by converting cells into spots which 
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            grow or shrink according to the intensity that cell needs to 
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            represent.
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          </p>
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              <p> 
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            Imagine a grid super-imposed on the original image.  The image 
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            is divided into cells by the grid - each cell will ultimately 
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            hold a single spot made up of multiple output pixels in order to 
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            approximate the darkness of the original image in that cell.
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          </p>
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              <p>
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            Obviously, a large cell size results in a heavy loss in 
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            resolution! The spots in the cells typically start off as 
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            circles, and grow to be diamond shaped.  This change in shape is 
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            controlled by a <span class="guilabel">spot function</span>.  By using 
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            different spot functions, the evolution in the shape of the 
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            spots as the cell goes from fully black to fully white may be 
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            controlled.
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          </p>
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            </dd>
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          </dl>
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        </div>
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      </div>
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      <div class="simplesect" lang="en" xml:lang="en">
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        <div class="titlepage">
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          <div>
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            <div>
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              <h4 class="title"><a id="id2981270"></a>Options</h4>
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            </div>
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          </div>
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          <div></div>
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        </div>
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        <div class="variablelist">
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          <dl>
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            <dt>
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              <span class="term">Resolution</span>
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            </dt>
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            <dd>
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              <p>
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            This group controls the cell size, either by setting the
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            input and output resolutions, or directly.
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          </p>
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              <div class="itemizedlist">
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                <ul type="disc">
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                  <li><span class="guilabel">Input SPI</span>: Resolution of the
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              original input image, in Samples Per Inch (SPI).  This
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              is automatically initialised to the input image's resolution.
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            </li>
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                  <li><span class="guilabel">Output LPI</span>: Desired output
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              resolution, in Lines Per Inch (LPI).
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            </li>
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                  <li><span class="guilabel">Cell Size</span>: Resulting cell size, in
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              pixels.  Most often you will want to set this directly.
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            </li>
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                </ul>
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              </div>
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            </dd>
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            <dt>
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              <span class="term">Screen</span>
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            </dt>
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            <dd>
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              <div class="itemizedlist">
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                <ul type="disc">
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                  <li>
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                    <p>
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                <span class="guilabel">Separate To RGB, CMYK,
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                Intensity</span>: Select which colourspace you
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                wish to operate in.  In <span class="emphasis"><em>RGB</em></span> mode, no 
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                colourspace conversion is performed. In 
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                <span class="emphasis"><em>CMYK</em></span>, the image is first
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                internally converted to CMYK, then each colour channel is
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                separately halftoned, before finally being
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                recombined back to an RGB image.  
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                In <span class="emphasis"><em>Intensity</em></span> mode, the
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                image is internally converted to greyscale,
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                halftoned, then the result used as the alpha channel
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                for the input image.  This is good for special
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                effects, but requires a little experimentation to
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                achieve best results.  Hint: try CMYK if you don't know
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                which to go for initially.
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              </p>
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                  </li>
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                  <li>
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                    <p>
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                <span class="guilabel">Black Pullout (%)</span> When doing
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              RGB-&gt;CMYK conversion, how much K (black) should be used?
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              </p>
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                  </li>
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                  <li>
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                    <p>
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                <span class="guilabel">Angle</span>: Cell grid angle for this channel.
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              </p>
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                  </li>
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                  <li>
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                    <p>
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                <span class="guilabel">Spot Function</span>: Spot function to
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                be used for this angle (see preview in blue cell-boxes).
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              </p>
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                  </li>
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                  <li>
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                    <p>
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                <span class="guilabel">Lock Channels</span>: Make channel
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                modifications apply to all channels.
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              </p>
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                  </li>
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                  <li>
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                    <p>
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                <span class="guilabel">Factory Defaults</span>: Restore the
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                default settings which should give pleasing results.
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              </p>
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                  </li>
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                </ul>
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              </div>
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            </dd>
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            <dt>
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              <span class="term">Antialiasing</span>
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            </dt>
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            <dd>
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              <p>
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          Proper halftoning does not need antialiasing: the aim is to
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          reduce the colour depth after all!  However, since this
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          plugin is mainly for special effects, the results are
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          displayed on screen rather than by a black/white printer.
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          So it is often useful to apply a little anti-aliasing to
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          simulate ink smearing on paper.  If you do want to print the
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          resulting image then set the antialising to 1 (ie, off).
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          </p>
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              <p>
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            <span class="guilabel">Oversample</span>:Number of subpixels to
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            sample to produce each output pixel.  Set to 1 to disable
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            this feature.  Warning: large numbers here will lead to
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            very long filter runtimes!
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          </p>
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            </dd>
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            <dt></dt>
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            <dd>
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              <div class="tip" style="margin-left: 0.5in; margin-right: 0.5in;">
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                <table border="0" summary="Tip">
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                  <tr>
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                    <td rowspan="2" align="center" valign="top" width="25">
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                      <img alt="[Tip]" src="../images/tip.png" />
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                    </td>
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                    <th align="left">Tip</th>
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                  </tr>
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                  <tr>
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                    <td colspan="2" align="left" valign="top">
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            More explanations, illustrative diagrams, a gallery and a
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            tutorial are to be found on the plug-in author site:
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            <a href="/cgi-bin/olink?sysid=">
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            <i class="citetitle">http://www.cl.cam.ac.uk/~and1000/newsprint/</i></a>  
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            You are strongly encouraged to visit it, since halftoning
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            is a large and complex area.
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          </td>
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                  </tr>
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                </table>
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              </div>
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            </dd>
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            <dt></dt>
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            <dd>
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              <p>
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            Here is an example, from the author's gallery:
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          </p>
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              <div class="mediaobject">
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                <img src="../images/filters/examples/newsprint.gif" />
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              </div>
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            </dd>
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          </dl>
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        </div>
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      </div>
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    </div>
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    <div class="navfooter">
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      <hr />
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      <table width="100%" summary="Navigation footer">
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        <tr>
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          <td width="40%" align="left"><a accesskey="p" href="ch05s10s10.html">Prev</a> </td>
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          <td width="20%" align="center">
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            <a accesskey="u" href="ch05s10.html">Up</a>
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          </td>
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          <td width="40%" align="right"> <a accesskey="n" href="ch05s10s12.html">Next</a></td>
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        </tr>
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        <tr>
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          <td width="40%" align="left" valign="top">10.10. Shift </td>
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          <td width="20%" align="center">
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            <a accesskey="h" href="index.html">Home</a>
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          </td>
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          <td width="40%" align="right" valign="top"> 10.12. Video</td>
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        </tr>
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      </table>
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    </div>
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  </body>
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</html>