documentation-sources/content/xdocs/using/transcoder.xml - xmlgraphics-batik - Git at Google

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 <!-- author tkormann@apache.org                                                -->
 <!-- version $Id: rasterizerTutorial.xml 327785 2005-10-23 12:38:58Z deweese $ -->
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 <!DOCTYPE document PUBLIC "-//APACHE//DTD Documentation V2.0//EN" "http://forrest.apache.org/dtd/document-v20.dtd">
 <document>
   <header>
     <title>Transcoder API</title>
   </header>

   <body>
     <p>
       The goal of the transcoder API (package
       <code>org.apache.batik.transcoder</code>) is to provide a generic
       API for transcoding an input to an output. First, this document
       explains the basic transcoder API that
       <a class="class" href="../javadoc/org/apache/batik/transcoder/Transcoder.html">Transcoder</a>,
       <a class="class" href="../javadoc/org/apache/batik/transcoder/TranscoderInput.html">TranscoderInput</a>
       and
       <a class="class" href="../javadoc/org/apache/batik/transcoder/TranscoderOutput.html">TranscoderOutput</a>
       define, and thus all transcoders have in common.  Next, it describes
       how to use the image transcoder API (package
       <code>org.apache.batik.transcoder.image</code>), which lets you
       rasterize an SVG document fragment to a raster image such as JPEG,
       PNG or TIFF.
     </p>

     <section id="transcoderAPI">
       <title>The transcoder API</title>
       <p>
         The <code>org.apache.batik.transcoder</code> package defines 5 major
         classes:
       </p>
       <dl>
         <dt>Transcoder</dt>
         <dd>
           <p>
             The
             <a class="class" href="../javadoc/org/apache/batik/transcoder/Transcoder.html">Transcoder</a>
             interface defines the interface that all transcoders implement. You can
             transcode a specific input using a specific output by invoking the
             <code>transcode</code> method. Although there is no assumption on the
             input and output format, a specific transcoder may or may not support
             a particular type of input or output. For example, the image
             transcoders accept an SVG
             <a class="class" href="http://java.sun.com/j2se/1.5.0/docs/api/org/w3c/dom/Document.html">Document</a>,
             a
             <a class="class" href="http://java.sun.com/j2se/1.5.0/docs/api/java/io/Reader.html">Reader</a>,
             an
             <a class="class" href="http://java.sun.com/j2se/1.5.0/docs/api/java/io/InputStream.html">InputStream</a>,
             or a
             <a class="class" href="http://java.sun.com/j2se/1.5.0/docs/api/java/net/URI.html">URI</a>
             as an input but only supports a byte stream for the output.
           </p>
         </dd>

         <dt>TranscoderInput</dt>
         <dd>
           <p>
             The
             <a class="class" href="../javadoc/org/apache/batik/transcoder/TranscoderInput.html">TranscoderInput</a>
             interface defines the input of a transcoder. There are various ways to create an
             input and the most common are already part of the API. The default
             implementation lets you create an input using a
             <code>org.w3c.dom.Document</code>, a <code>Reader</code>, an
             <code>InputStream</code>, a <code>org.xml.sax.XMLReader</code>, or a
             <code>URI</code>.
           </p>
         </dd>

         <dt>TranscoderOutput</dt>
         <dd>
           <p>
             The
             <a class="class" href="../javadoc/org/apache/batik/transcoder/TranscoderOutput.html">TranscoderOutput</a>
             interface defines the output of a transcoder. There are various ways to create an
             output and the most commons are already part of the API. The default
             implementation lets you create an output using a
             <a class="class" href="http://java.sun.com/j2se/1.5.0/docs/api/org/w3c/dom/Document.html">Document</a>,
             a
             <a class="class" href="http://java.sun.com/j2se/1.5.0/docs/api/java/io/Writer.html">Writer</a>,
             an
             <a class="class" href="http://java.sun.com/j2se/1.5.0/docs/api/java/io/OutputStream.html">OutputStream</a>,
             a
             <a class="class" href="http://java.sun.com/j2se/1.5.0/docs/api/org/xml/sax/XMLFilter.html">XMLFilter</a>,
             or a
             <a class="class" href="http://java.sun.com/j2se/1.5.0/docs/api/java/net/URI.html">URI</a>.
           </p>
         </dd>

         <dt>TranscodingHints</dt>
         <dd>
           <p>
             The
             <a class="class" href="../javadoc/org/apache/batik/transcoder/TranscodingHints.html">TranscodingHints</a>
             class contains different hints that can be used to control
             the various options or parameters of a transcoder. Each transcoder
             provides its own set of hints. A hint is specified by (key, value)
             pair. For example, the
             <a class="class" href="../javadoc/org/apache/batik/transcoder/image/JPEGTranscoder.html">JPEGTranscoder</a>
             provides a hint to control the encoding quality.
           </p>
         </dd>

         <dt>ErrorHandler</dt>
         <dd>
           <p>
             The
             <a class="class" href="../javadoc/org/apache/batik/transcoder/ErrorHandler.html">ErrorHandler</a>
             class provides a way to get any errors or warnings that might
             occur while transcoding. A default implementation is provided but
             you can, for example, implement your own handler that displays a dialog
             instead of stack trace.
           </p>
         </dd>
       </dl>
     </section>

     <section id="howtousetranscoderAPI">
       <title>How to use the image transcoder API</title>
       <p>
         The <code>org.apache.batik.transcoder.image</code> package provides an
         easy way to transcode an SVG document to a raster image such as JPEG,
         PNG or TIFF. Additional raster image formats can be added by
         subclassing the <code>ImageTranscoder</code> class and implementing the
         <code>writeImage</code> method. Although, in next sections, the
         examples will use the JPEG transcoder, the PNG transcoder works the
         same way.
       </p>

       <section id="createImage">
         <title>Creating an image</title>
         <p>
           The following example, using the <code>JPEGTranscoder</code>, shows how to
           transform an SVG document to a JPEG image.
         </p>
       <source>import java.io.*;

 import org.apache.batik.transcoder.image.JPEGTranscoder;
 import org.apache.batik.transcoder.TranscoderInput;
 import org.apache.batik.transcoder.TranscoderOutput;

 public class SaveAsJPEG {

     public static void main(String[] args) throws Exception {

         // Create a JPEG transcoder
         <strong>JPEGTranscoder t = new JPEGTranscoder();</strong>

         // Set the transcoding hints.
         <strong>t.addTranscodingHint(JPEGTranscoder.KEY_QUALITY,
                              new Float(.8));</strong>

         // Create the transcoder input.
         String svgURI = new File(args[0]).toURL().toString();
         <strong>TranscoderInput input = new TranscoderInput(svgURI);</strong>

         // Create the transcoder output.
         OutputStream ostream = new FileOutputStream("out.jpg");
         <strong>TranscoderOutput output = new TranscoderOutput(ostream);</strong>

         // Save the image.
         <strong>t.transcode(input, output);</strong>

         // Flush and close the stream.
         ostream.flush();
         ostream.close();
         System.exit(0);
     }
 }</source>
       <p>
         The code creates a <code>JPEGTranscoder</code> and sets a
         transcoding hint. The hint indicates the encoding quality. Then, an
         input and an output are created. The input is created using the first
         command line argument, which should be a URI. The output is a byte
         stream for a file called <code>out.jpg</code>. Finally, the
         <code>transcode</code> method is invoked and the byte stream is
         closed.
       </p>
       <p>
         Although not shown above, the program might have specified additional
         hints to indicate a user stylesheet, the preferred language of the
         document or the background color.
       </p>
       <p>
         To try this program:
       </p>
       <ol>
         <li>
           <p>Save the above program as <code>SaveAsJPEG.java</code>. </p>
         </li>
         <li>
           <p>Compile the program.</p>
         </li>
         <li>
           <p>Choose an SVG file to transcode, and perform the transcoding by running:</p>
           <source>java SaveAsJPEG <em>filename</em>.svg</source>
         </li>
         <li>
           <p>Inspect the output file <code>out.jpg</code>.</p>
         </li>
       </ol>
     </section>

     <section id="defineSizeOfImage">
       <title>Defining the size of the image</title>
       <p>
         By adding the following line of code to the previous example, you will
         specify the raster image size (in pixels). The transcoding hint
         <code>KEY_WIDTH</code> lets you specify the raster image width. If the
         raster image height is not provided (using the <code>KEY_HEIGHT</code>),
         the transcoder will compute the raster image height by keeping the
         aspect ratio of the SVG document.
       </p>
       <source>t.addTranscodingHint(JPEGTranscoder.KEY_WIDTH, new Float(100));</source>
       <p>
         The transcoder will have the same behavior if you specify the
         <code>KEY_HEIGHT</code> without initializing the
         <code>KEY_WIDTH</code>. In all cases (even if both keys are provided),
         the transcoder will preserve the apsect ratio of the SVG document.
       </p>
     </section>

     <section id="selectAreaOfIntrest">
       <title>Selecting an area of interest</title>
       <p>
         The image transcoder lets you specify an area of interest (that is, a
         part of the SVG document). The key <code>KEY_AOI</code> allows you to
         select the region of the SVG document to render. The value of this key must
         be a
         <a class="class" href="http://java.sun.com/j2se/1.5.0/docs/api/java/awt/Rectangle.html">java.awt.Rectangle</a>
         specified in pixels, using the coordinate space of the SVG document. The
         following example shows how you can split an SVG document into 4 tiles.
       </p>
       <source>import java.io.*;
 import java.awt.*;

 import org.apache.batik.transcoder.image.JPEGTranscoder;
 import org.apache.batik.transcoder.TranscoderInput;
 import org.apache.batik.transcoder.TranscoderOutput;

 public class SaveAsJPEGTiles {

     JPEGTranscoder trans = new JPEGTranscoder();

     public SaveAsJPEGTiles() {
         trans.addTranscodingHint(JPEGTranscoder.KEY_QUALITY,
                                  new Float(.8));
     }

     public void tile(String inputFilename,
                      String outputFilename,
                      Rectangle aoi) throws Exception {
         // Set hints to indicate the dimensions of the output image
         // and the input area of interest.
         <strong>trans.addTranscodingHint(JPEGTranscoder.KEY_WIDTH,
                                  new Float(aoi.width));</strong>
         <strong>trans.addTranscodingHint(JPEGTranscoder.KEY_HEIGHT,
                                  new Float(aoi.height));</strong>
         <strong>trans.addTranscodingHint(JPEGTranscoder.KEY_AOI, aoi);</strong>

         // Transcode the file.
         String svgURI = new File(inputFilename).toURL().toString();
         TranscoderInput input = new TranscoderInput(svgURI);
         OutputStream ostream = new FileOutputStream(outputFilename);
         TranscoderOutput output = new TranscoderOutput(ostream);
         trans.transcode(input, output);

         // Flush and close the output.
         ostream.flush();
         ostream.close();
     }

     public static void main(String[] args) throws Exception {
         // Rasterize the samples/anne.svg document and save it
         // as four tiles.
         SaveAsJPEGTiles p = new SaveAsJPEGTiles();
         <strong>String in = "samples/anne.svg";
         int documentWidth = 450;
         int documentHeight = 500;</strong>
         int dw2 = documentWidth / 2;
         int dh2 = documentHeight / 2;
         p.tile(in, "tileTopLeft.jpg", new Rectangle(0, 0, dw2, dh2));
         p.tile(in, "tileTopRight.jpg", new Rectangle(dw2, 0, dw2, dh2));
         p.tile(in, "tileBottomLeft.jpg", new Rectangle(0, dh2, dw2, dh2));
         p.tile(in, "tileBottomRight.jpg", new Rectangle(dw2, dh2, dw2, dh2));
         System.exit(0);
     }
 }</source>
       <p>
         This code splits the same document <code>anne.svg</code> into four
         tiles of the same size. Considering the document and its original
         size, we can determine four regions. Then we rasterize each region
         using the <code>KEY_AOI</code> key. Note that we also specify the
         image width and height to be the same as the area of interest width and
         height (so we keep a 1:1 zoom factor). You can of course use different
         values for the <code>KEY_WIDTH</code> and <code>KEY_HEIGHT</code>, that
         do not match the dimensions of the <code>KEY_AOI</code> key. In that
         case, first the area of interest will determine which part of the SVG
         document has to be rendered, then that part could be zoomed in or out
         depending on the specified raster image size.
       </p>
       <p>
         To try this program:
       </p>
       <ol>
         <li><p>Save the above program as <code>SaveAsJPEGTiles.java</code>.</p></li>
         <li><p>Compile the program.</p></li>
         <li><p>Copy the <code>samples/anne.svg</code> document from the Batik
             distribution into the current directory.</p></li>
         <li>
           <p>Run the program by typing:</p>
           <source>java SaveAsJPEGTiles</source>
         </li>
         <li>
           <p>
             Inspect the output files <code>tileTopRight.jpg</code>,
             <code>tileTopRight.jpg</code>, <code>tileBottomRight.jpg</code>
             and <code>tileBottomLeft.jpg</code>.
           </p>
         </li>
       </ol>
     </section>

     <section id="otherTransHints">
       <title>Other transcoding hints</title>
       <p>
         The <code>ImageTranscoder</code> provides additional
         <code>TranscodingHints</code> that let you customize the generated
         images.
       </p>
       <dl>
         <dt><code>ImageTranscoder.KEY_MEDIA</code></dt>
         <dd>
           <p>
             This hint lets you choose the CSS medium to use. The author of the SVG document
             to transcode can control CSS media using the
             <a href="http://www.w3.org/TR/REC-CSS2/media.html">CSS media rule</a>.
             For example:
           </p>
           <source>trans.addTranscodingHint(ImageTranscoder.KEY_MEDIA, "print");</source>
         </dd>

         <dt><code>ImageTranscoder.KEY_ALTERNATE_STYLESHEET</code></dt>
         <dd>
           <p>
             This hint lets you choose an alternate stylesheet the author of the SVG
             document to transcode might have provided using the
             <a href="http://www.w3.org/TR/xml-stylesheet/">xml-stylesheet</a>
             processing instruction. For exxample:
           </p>
           <source>trans.addTranscodingHint(ImageTranscoder.KEY_ALTERNATE_STYLESHEET,
                          alternateStylesheetName);</source>
         </dd>

         <dt><code>ImageTranscoder.KEY_USER_STYLESHEET_URI</code></dt>
         <dd>
           <p>
             This hint lets you use a user stylesheet. A user stylesheet can override some
             styles of the SVG document to transcode. For example:
           </p>
           <source>trans.addTranscodingHint(ImageTranscoder.KEY_USER_STYLESHEET_URI, "http://...");</source>
         </dd>

         <dt><code>ImageTranscoder.KEY_PIXEL_TO_MM</code></dt>
         <dd>
           <p>
             This hint lets you use the pixel to millimeter conversion factor.
             This factor is used to determine how units are converted into
             pixels.  For example:
           </p>
           <source>// 96dpi
 trans.addTranscodingHint(ImageTranscoder.KEY_PIXEL_TO_MM, new Float(0.2645833f));</source>
           <p>or</p>
           <source>// 72pi
 trans.addTranscodingHint(ImageTranscoder.KEY_PIXEL_TO_MM, new Float(0.3528f));</source>
         </dd>

         <dt><code>ImageTranscoder.KEY_BACKGROUND_COLOR</code></dt>
         <dd>
           <p>
             This hint lets you choose a background color. For example:
           </p>
           <source>trans.addTranscodingHint(ImageTranscoder.KEY_BACKGROUND_COLOR, Color.white);</source>
         </dd>
       </dl>
     </section>

     <section id="genImagefromSVGDOM">
       <title>Generating an image from an SVG DOM tree</title>
       <p>
         The following code creates and saves an SVG DOM tree to
         a raster image.
       </p>
 <source>import java.io.*;

 import org.apache.batik.transcoder.image.JPEGTranscoder;
 import org.apache.batik.transcoder.TranscoderInput;
 import org.apache.batik.transcoder.TranscoderOutput;
 import org.apache.batik.dom.svg.SVGDOMImplementation;

 import org.w3c.dom.Document;
 import org.w3c.dom.Element;
 import org.w3c.dom.DOMImplementation;

 public class DOMRasterizer {

     public Document createDocument() {

         // Create a new document.
         <strong>DOMImplementation impl = SVGDOMImplementation.getDOMImplementation();
         String svgNS = SVGDOMImplementation.SVG_NAMESPACE_URI;
         Document document =
             impl.createDocument(svgNS, "svg", null);
         Element root = document.getDocumentElement();</strong>
         root.setAttributeNS(null, "width", "450");
         root.setAttributeNS(null, "height", "500");

         // Add some content to the document.
         Element e;
         e = document.createElementNS(svgNS, "rect");
         e.setAttributeNS(null, "x", "10");
         e.setAttributeNS(null, "y", "10");
         e.setAttributeNS(null, "width", "200");
         e.setAttributeNS(null, "height", "300");
         e.setAttributeNS(null, "style", "fill:red;stroke:black;stroke-width:4");
         root.appendChild(e);

         e = document.createElementNS(svgNS, "circle");
         e.setAttributeNS(null, "cx", "225");
         e.setAttributeNS(null, "cy", "250");
         e.setAttributeNS(null, "r", "100");
         e.setAttributeNS(null, "style", "fill:green;fill-opacity:.5");
         root.appendChild(e);

         return document;
     }

     public void save(Document document) throws Exception {

         // Create a JPEGTranscoder and set its quality hint.
         JPEGTranscoder t = new JPEGTranscoder();
         t.addTranscodingHint(JPEGTranscoder.KEY_QUALITY,
                              new Float(.8));

         // Set the transcoder input and output.
         <strong>TranscoderInput input = new TranscoderInput(document);</strong>
         OutputStream ostream = new FileOutputStream("out.jpg");
         TranscoderOutput output = new TranscoderOutput(ostream);

         // Perform the transcoding.
         t.transcode(input, output);
         ostream.flush();
         ostream.close();
     }

     public static void main(String[] args) throws Exception {
         // Runs the example.
         DOMRasterizer rasterizer = new DOMRasterizer();
         Document document = rasterizer.createDocument();
         rasterizer.save(document);
         System.exit(0);
     }
 }
 </source>
       <p>
         This code is divided into two distinct parts.
       </p>
       <dl>
         <dt>Creating an SVG DOM tree</dt>
         <dd>
           <p>See the <code>createDocument</code> method.</p>
           <p>
             Three steps are required at this time. The first step is to
             get the Batik SVG DOM implementation (via the
             <code>SVGDOMImplementation</code> class). Then, you can create a
             <code>org.w3c.dom.Document</code> (which also implements the
             <code>SVGDocument</code> interface) by invoking the
             <code>createDocument</code> method with the SVG namespace URI and
             the <code>svg</code> document element name. Finally, you can get
             the document element and start building your DOM tree.
           </p>
         </dd>
         <dt>Rasterizing the DOM</dt>
         <dd>
           <p>See the <code>save</code> method.</p>
           <p>
             Similar to the previous examples, you can transcode an SVG
             document to a raster image by creating a
             <code>TranscoderInput</code>, but passing to it the SVG Document
             this time.
           </p>
         </dd>
       </dl>
       <p>
         To try this example:
       </p>
       <ol>
         <li><p>Save the code as <code>DOMRasterizer.java</code>.</p></li>
         <li><p>Compile the program.</p></li>
         <li><p>Run it, by typingL</p>
           <source>java DOMRasterizer</source></li>
         <li><p>Inspect the output file <code>out.jpg</code>.</p></li>
       </ol>
     </section>
   </section>

 </body>
 </document>
	<?xml version="1.0"?>

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	contributor license agreements. See the NOTICE file distributed with
	this work for additional information regarding copyright ownership.
	The ASF licenses this file to You under the Apache License, Version 2.0
	(the "License"); you may not use this file except in compliance with
	the License. You may obtain a copy of the License at

	http://www.apache.org/licenses/LICENSE-2.0

	Unless required by applicable law or agreed to in writing, software
	distributed under the License is distributed on an "AS IS" BASIS,
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	See the License for the specific language governing permissions and
	limitations under the License.

	-->

	<!-- ========================================================================= -->
	<!-- author tkormann@apache.org -->
	<!-- version $Id: rasterizerTutorial.xml 327785 2005-10-23 12:38:58Z deweese $ -->
	<!-- ========================================================================= -->

	<!DOCTYPE document PUBLIC "-//APACHE//DTD Documentation V2.0//EN" "http://forrest.apache.org/dtd/document-v20.dtd">
	<document>
	<header>
	<title>Transcoder API</title>
	</header>

	<body>
	<p>
	The goal of the transcoder API (package
	<code>org.apache.batik.transcoder</code>) is to provide a generic
	API for transcoding an input to an output. First, this document
	explains the basic transcoder API that
	<a class="class" href="../javadoc/org/apache/batik/transcoder/Transcoder.html">Transcoder</a>,
	<a class="class" href="../javadoc/org/apache/batik/transcoder/TranscoderInput.html">TranscoderInput</a>
	and
	<a class="class" href="../javadoc/org/apache/batik/transcoder/TranscoderOutput.html">TranscoderOutput</a>
	define, and thus all transcoders have in common. Next, it describes
	how to use the image transcoder API (package
	<code>org.apache.batik.transcoder.image</code>), which lets you
	rasterize an SVG document fragment to a raster image such as JPEG,
	PNG or TIFF.
	</p>

	<section id="transcoderAPI">
	<title>The transcoder API</title>
	<p>
	The <code>org.apache.batik.transcoder</code> package defines 5 major
	classes:
	</p>
	<dl>
	<dt>Transcoder</dt>
	<dd>
	<p>
	The
	<a class="class" href="../javadoc/org/apache/batik/transcoder/Transcoder.html">Transcoder</a>
	interface defines the interface that all transcoders implement. You can
	transcode a specific input using a specific output by invoking the
	<code>transcode</code> method. Although there is no assumption on the
	input and output format, a specific transcoder may or may not support
	a particular type of input or output. For example, the image
	transcoders accept an SVG
	<a class="class" href="http://java.sun.com/j2se/1.5.0/docs/api/org/w3c/dom/Document.html">Document</a>,
	a
	<a class="class" href="http://java.sun.com/j2se/1.5.0/docs/api/java/io/Reader.html">Reader</a>,
	an
	<a class="class" href="http://java.sun.com/j2se/1.5.0/docs/api/java/io/InputStream.html">InputStream</a>,
	or a
	<a class="class" href="http://java.sun.com/j2se/1.5.0/docs/api/java/net/URI.html">URI</a>
	as an input but only supports a byte stream for the output.
	</p>
	</dd>

	<dt>TranscoderInput</dt>
	<dd>
	<p>
	The
	<a class="class" href="../javadoc/org/apache/batik/transcoder/TranscoderInput.html">TranscoderInput</a>
	interface defines the input of a transcoder. There are various ways to create an
	input and the most common are already part of the API. The default
	implementation lets you create an input using a
	<code>org.w3c.dom.Document</code>, a <code>Reader</code>, an
	<code>InputStream</code>, a <code>org.xml.sax.XMLReader</code>, or a
	<code>URI</code>.
	</p>
	</dd>

	<dt>TranscoderOutput</dt>
	<dd>
	<p>
	The
	<a class="class" href="../javadoc/org/apache/batik/transcoder/TranscoderOutput.html">TranscoderOutput</a>
	interface defines the output of a transcoder. There are various ways to create an
	output and the most commons are already part of the API. The default
	implementation lets you create an output using a
	<a class="class" href="http://java.sun.com/j2se/1.5.0/docs/api/org/w3c/dom/Document.html">Document</a>,
	a
	<a class="class" href="http://java.sun.com/j2se/1.5.0/docs/api/java/io/Writer.html">Writer</a>,
	an
	<a class="class" href="http://java.sun.com/j2se/1.5.0/docs/api/java/io/OutputStream.html">OutputStream</a>,
	a
	<a class="class" href="http://java.sun.com/j2se/1.5.0/docs/api/org/xml/sax/XMLFilter.html">XMLFilter</a>,
	or a
	<a class="class" href="http://java.sun.com/j2se/1.5.0/docs/api/java/net/URI.html">URI</a>.
	</p>
	</dd>

	<dt>TranscodingHints</dt>
	<dd>
	<p>
	The
	<a class="class" href="../javadoc/org/apache/batik/transcoder/TranscodingHints.html">TranscodingHints</a>
	class contains different hints that can be used to control
	the various options or parameters of a transcoder. Each transcoder
	provides its own set of hints. A hint is specified by (key, value)
	pair. For example, the
	<a class="class" href="../javadoc/org/apache/batik/transcoder/image/JPEGTranscoder.html">JPEGTranscoder</a>
	provides a hint to control the encoding quality.
	</p>
	</dd>

	<dt>ErrorHandler</dt>
	<dd>
	<p>
	The
	<a class="class" href="../javadoc/org/apache/batik/transcoder/ErrorHandler.html">ErrorHandler</a>
	class provides a way to get any errors or warnings that might
	occur while transcoding. A default implementation is provided but
	you can, for example, implement your own handler that displays a dialog
	instead of stack trace.
	</p>
	</dd>
	</dl>
	</section>

	<section id="howtousetranscoderAPI">
	<title>How to use the image transcoder API</title>
	<p>
	The <code>org.apache.batik.transcoder.image</code> package provides an
	easy way to transcode an SVG document to a raster image such as JPEG,
	PNG or TIFF. Additional raster image formats can be added by
	subclassing the <code>ImageTranscoder</code> class and implementing the
	<code>writeImage</code> method. Although, in next sections, the
	examples will use the JPEG transcoder, the PNG transcoder works the
	same way.
	</p>

	<section id="createImage">
	<title>Creating an image</title>
	<p>
	The following example, using the <code>JPEGTranscoder</code>, shows how to
	transform an SVG document to a JPEG image.
	</p>
	<source>import java.io.*;

	import org.apache.batik.transcoder.image.JPEGTranscoder;
	import org.apache.batik.transcoder.TranscoderInput;
	import org.apache.batik.transcoder.TranscoderOutput;

	public class SaveAsJPEG {

	public static void main(String[] args) throws Exception {

	// Create a JPEG transcoder
	<strong>JPEGTranscoder t = new JPEGTranscoder();</strong>

	// Set the transcoding hints.
	<strong>t.addTranscodingHint(JPEGTranscoder.KEY_QUALITY,
	new Float(.8));</strong>

	// Create the transcoder input.
	String svgURI = new File(args[0]).toURL().toString();
	<strong>TranscoderInput input = new TranscoderInput(svgURI);</strong>

	// Create the transcoder output.
	OutputStream ostream = new FileOutputStream("out.jpg");
	<strong>TranscoderOutput output = new TranscoderOutput(ostream);</strong>

	// Save the image.
	<strong>t.transcode(input, output);</strong>

	// Flush and close the stream.
	ostream.flush();
	ostream.close();
	System.exit(0);
	}
	}</source>
	<p>
	The code creates a <code>JPEGTranscoder</code> and sets a
	transcoding hint. The hint indicates the encoding quality. Then, an
	input and an output are created. The input is created using the first
	command line argument, which should be a URI. The output is a byte
	stream for a file called <code>out.jpg</code>. Finally, the
	<code>transcode</code> method is invoked and the byte stream is
	closed.
	</p>
	<p>
	Although not shown above, the program might have specified additional
	hints to indicate a user stylesheet, the preferred language of the
	document or the background color.
	</p>
	<p>
	To try this program:
	</p>
	<ol>
	<li>
	<p>Save the above program as <code>SaveAsJPEG.java</code>. </p>
	</li>
	<li>
	<p>Compile the program.</p>
	</li>
	<li>
	<p>Choose an SVG file to transcode, and perform the transcoding by running:</p>
	<source>java SaveAsJPEG <em>filename</em>.svg</source>
	</li>
	<li>
	<p>Inspect the output file <code>out.jpg</code>.</p>
	</li>
	</ol>
	</section>

	<section id="defineSizeOfImage">
	<title>Defining the size of the image</title>
	<p>
	By adding the following line of code to the previous example, you will
	specify the raster image size (in pixels). The transcoding hint
	<code>KEY_WIDTH</code> lets you specify the raster image width. If the
	raster image height is not provided (using the <code>KEY_HEIGHT</code>),
	the transcoder will compute the raster image height by keeping the
	aspect ratio of the SVG document.
	</p>
	<source>t.addTranscodingHint(JPEGTranscoder.KEY_WIDTH, new Float(100));</source>
	<p>
	The transcoder will have the same behavior if you specify the
	<code>KEY_HEIGHT</code> without initializing the
	<code>KEY_WIDTH</code>. In all cases (even if both keys are provided),
	the transcoder will preserve the apsect ratio of the SVG document.
	</p>
	</section>

	<section id="selectAreaOfIntrest">
	<title>Selecting an area of interest</title>
	<p>
	The image transcoder lets you specify an area of interest (that is, a
	part of the SVG document). The key <code>KEY_AOI</code> allows you to
	select the region of the SVG document to render. The value of this key must
	be a
	<a class="class" href="http://java.sun.com/j2se/1.5.0/docs/api/java/awt/Rectangle.html">java.awt.Rectangle</a>
	specified in pixels, using the coordinate space of the SVG document. The
	following example shows how you can split an SVG document into 4 tiles.
	</p>
	<source>import java.io.*;
	import java.awt.*;

	import org.apache.batik.transcoder.image.JPEGTranscoder;
	import org.apache.batik.transcoder.TranscoderInput;
	import org.apache.batik.transcoder.TranscoderOutput;

	public class SaveAsJPEGTiles {

	JPEGTranscoder trans = new JPEGTranscoder();

	public SaveAsJPEGTiles() {
	trans.addTranscodingHint(JPEGTranscoder.KEY_QUALITY,
	new Float(.8));
	}

	public void tile(String inputFilename,
	String outputFilename,
	Rectangle aoi) throws Exception {
	// Set hints to indicate the dimensions of the output image
	// and the input area of interest.
	<strong>trans.addTranscodingHint(JPEGTranscoder.KEY_WIDTH,
	new Float(aoi.width));</strong>
	<strong>trans.addTranscodingHint(JPEGTranscoder.KEY_HEIGHT,
	new Float(aoi.height));</strong>
	<strong>trans.addTranscodingHint(JPEGTranscoder.KEY_AOI, aoi);</strong>

	// Transcode the file.
	String svgURI = new File(inputFilename).toURL().toString();
	TranscoderInput input = new TranscoderInput(svgURI);
	OutputStream ostream = new FileOutputStream(outputFilename);
	TranscoderOutput output = new TranscoderOutput(ostream);
	trans.transcode(input, output);

	// Flush and close the output.
	ostream.flush();
	ostream.close();
	}

	public static void main(String[] args) throws Exception {
	// Rasterize the samples/anne.svg document and save it
	// as four tiles.
	SaveAsJPEGTiles p = new SaveAsJPEGTiles();
	<strong>String in = "samples/anne.svg";
	int documentWidth = 450;
	int documentHeight = 500;</strong>
	int dw2 = documentWidth / 2;
	int dh2 = documentHeight / 2;
	p.tile(in, "tileTopLeft.jpg", new Rectangle(0, 0, dw2, dh2));
	p.tile(in, "tileTopRight.jpg", new Rectangle(dw2, 0, dw2, dh2));
	p.tile(in, "tileBottomLeft.jpg", new Rectangle(0, dh2, dw2, dh2));
	p.tile(in, "tileBottomRight.jpg", new Rectangle(dw2, dh2, dw2, dh2));
	System.exit(0);
	}
	}</source>
	<p>
	This code splits the same document <code>anne.svg</code> into four
	tiles of the same size. Considering the document and its original
	size, we can determine four regions. Then we rasterize each region
	using the <code>KEY_AOI</code> key. Note that we also specify the
	image width and height to be the same as the area of interest width and
	height (so we keep a 1:1 zoom factor). You can of course use different
	values for the <code>KEY_WIDTH</code> and <code>KEY_HEIGHT</code>, that
	do not match the dimensions of the <code>KEY_AOI</code> key. In that
	case, first the area of interest will determine which part of the SVG
	document has to be rendered, then that part could be zoomed in or out
	depending on the specified raster image size.
	</p>
	<p>
	To try this program:
	</p>
	<ol>
	<li><p>Save the above program as <code>SaveAsJPEGTiles.java</code>.</p></li>
	<li><p>Compile the program.</p></li>
	<li><p>Copy the <code>samples/anne.svg</code> document from the Batik
	distribution into the current directory.</p></li>
	<li>
	<p>Run the program by typing:</p>
	<source>java SaveAsJPEGTiles</source>
	</li>
	<li>
	<p>
	Inspect the output files <code>tileTopRight.jpg</code>,
	<code>tileTopRight.jpg</code>, <code>tileBottomRight.jpg</code>
	and <code>tileBottomLeft.jpg</code>.
	</p>
	</li>
	</ol>
	</section>

	<section id="otherTransHints">
	<title>Other transcoding hints</title>
	<p>
	The <code>ImageTranscoder</code> provides additional
	<code>TranscodingHints</code> that let you customize the generated
	images.
	</p>
	<dl>
	<dt><code>ImageTranscoder.KEY_MEDIA</code></dt>
	<dd>
	<p>
	This hint lets you choose the CSS medium to use. The author of the SVG document
	to transcode can control CSS media using the
	<a href="http://www.w3.org/TR/REC-CSS2/media.html">CSS media rule</a>.
	For example:
	</p>
	<source>trans.addTranscodingHint(ImageTranscoder.KEY_MEDIA, "print");</source>
	</dd>

	<dt><code>ImageTranscoder.KEY_ALTERNATE_STYLESHEET</code></dt>
	<dd>
	<p>
	This hint lets you choose an alternate stylesheet the author of the SVG
	document to transcode might have provided using the
	<a href="http://www.w3.org/TR/xml-stylesheet/">xml-stylesheet</a>
	processing instruction. For exxample:
	</p>
	<source>trans.addTranscodingHint(ImageTranscoder.KEY_ALTERNATE_STYLESHEET,
	alternateStylesheetName);</source>
	</dd>

	<dt><code>ImageTranscoder.KEY_USER_STYLESHEET_URI</code></dt>
	<dd>
	<p>
	This hint lets you use a user stylesheet. A user stylesheet can override some
	styles of the SVG document to transcode. For example:
	</p>
	<source>trans.addTranscodingHint(ImageTranscoder.KEY_USER_STYLESHEET_URI, "http://...");</source>
	</dd>

	<dt><code>ImageTranscoder.KEY_PIXEL_TO_MM</code></dt>
	<dd>
	<p>
	This hint lets you use the pixel to millimeter conversion factor.
	This factor is used to determine how units are converted into
	pixels. For example:
	</p>
	<source>// 96dpi
	trans.addTranscodingHint(ImageTranscoder.KEY_PIXEL_TO_MM, new Float(0.2645833f));</source>
	<p>or</p>
	<source>// 72pi
	trans.addTranscodingHint(ImageTranscoder.KEY_PIXEL_TO_MM, new Float(0.3528f));</source>
	</dd>

	<dt><code>ImageTranscoder.KEY_BACKGROUND_COLOR</code></dt>
	<dd>
	<p>
	This hint lets you choose a background color. For example:
	</p>
	<source>trans.addTranscodingHint(ImageTranscoder.KEY_BACKGROUND_COLOR, Color.white);</source>
	</dd>
	</dl>
	</section>

	<section id="genImagefromSVGDOM">
	<title>Generating an image from an SVG DOM tree</title>
	<p>
	The following code creates and saves an SVG DOM tree to
	a raster image.
	</p>
	<source>import java.io.*;

	import org.apache.batik.transcoder.image.JPEGTranscoder;
	import org.apache.batik.transcoder.TranscoderInput;
	import org.apache.batik.transcoder.TranscoderOutput;
	import org.apache.batik.dom.svg.SVGDOMImplementation;

	import org.w3c.dom.Document;
	import org.w3c.dom.Element;
	import org.w3c.dom.DOMImplementation;

	public class DOMRasterizer {

	public Document createDocument() {

	// Create a new document.
	<strong>DOMImplementation impl = SVGDOMImplementation.getDOMImplementation();
	String svgNS = SVGDOMImplementation.SVG_NAMESPACE_URI;
	Document document =
	impl.createDocument(svgNS, "svg", null);
	Element root = document.getDocumentElement();</strong>
	root.setAttributeNS(null, "width", "450");
	root.setAttributeNS(null, "height", "500");

	// Add some content to the document.
	Element e;
	e = document.createElementNS(svgNS, "rect");
	e.setAttributeNS(null, "x", "10");
	e.setAttributeNS(null, "y", "10");
	e.setAttributeNS(null, "width", "200");
	e.setAttributeNS(null, "height", "300");
	e.setAttributeNS(null, "style", "fill:red;stroke:black;stroke-width:4");
	root.appendChild(e);

	e = document.createElementNS(svgNS, "circle");
	e.setAttributeNS(null, "cx", "225");
	e.setAttributeNS(null, "cy", "250");
	e.setAttributeNS(null, "r", "100");
	e.setAttributeNS(null, "style", "fill:green;fill-opacity:.5");
	root.appendChild(e);

	return document;
	}

	public void save(Document document) throws Exception {

	// Create a JPEGTranscoder and set its quality hint.
	JPEGTranscoder t = new JPEGTranscoder();
	t.addTranscodingHint(JPEGTranscoder.KEY_QUALITY,
	new Float(.8));

	// Set the transcoder input and output.
	<strong>TranscoderInput input = new TranscoderInput(document);</strong>
	OutputStream ostream = new FileOutputStream("out.jpg");
	TranscoderOutput output = new TranscoderOutput(ostream);

	// Perform the transcoding.
	t.transcode(input, output);
	ostream.flush();
	ostream.close();
	}

	public static void main(String[] args) throws Exception {
	// Runs the example.
	DOMRasterizer rasterizer = new DOMRasterizer();
	Document document = rasterizer.createDocument();
	rasterizer.save(document);
	System.exit(0);
	}
	}
	</source>
	<p>
	This code is divided into two distinct parts.
	</p>
	<dl>
	<dt>Creating an SVG DOM tree</dt>
	<dd>
	<p>See the <code>createDocument</code> method.</p>
	<p>
	Three steps are required at this time. The first step is to
	get the Batik SVG DOM implementation (via the
	<code>SVGDOMImplementation</code> class). Then, you can create a
	<code>org.w3c.dom.Document</code> (which also implements the
	<code>SVGDocument</code> interface) by invoking the
	<code>createDocument</code> method with the SVG namespace URI and
	the <code>svg</code> document element name. Finally, you can get
	the document element and start building your DOM tree.
	</p>
	</dd>
	<dt>Rasterizing the DOM</dt>
	<dd>
	<p>See the <code>save</code> method.</p>
	<p>
	Similar to the previous examples, you can transcode an SVG
	document to a raster image by creating a
	<code>TranscoderInput</code>, but passing to it the SVG Document
	this time.
	</p>
	</dd>
	</dl>
	<p>
	To try this example:
	</p>
	<ol>
	<li><p>Save the code as <code>DOMRasterizer.java</code>.</p></li>
	<li><p>Compile the program.</p></li>
	<li><p>Run it, by typingL</p>
	<source>java DOMRasterizer</source></li>
	<li><p>Inspect the output file <code>out.jpg</code>.</p></li>
	</ol>
	</section>
	</section>

	</body>
	</document>