http://xmlgraphics.apache.org/batik/batik-transcoder/: Batik SVG transcoder (Apache Software Foundation) 
/*

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

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   See the License for the specific language governing permissions and
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package org.apache.batik.transcoder.image;

import java.awt.AlphaComposite;
import java.awt.Graphics2D;
import java.awt.Paint;
import java.awt.Shape;
import java.awt.geom.AffineTransform;
import java.awt.geom.Rectangle2D;
import java.awt.image.BufferedImage;
import java.awt.image.DataBufferInt;
import java.awt.image.SinglePixelPackedSampleModel;

import org.apache.batik.ext.awt.image.GraphicsUtil;
import org.apache.batik.gvt.renderer.ConcreteImageRendererFactory;
import org.apache.batik.gvt.renderer.ImageRenderer;
import org.apache.batik.gvt.renderer.ImageRendererFactory;
import org.apache.batik.transcoder.SVGAbstractTranscoder;
import org.apache.batik.transcoder.TranscoderException;
import org.apache.batik.transcoder.TranscoderOutput;
import org.apache.batik.transcoder.TranscodingHints;
import org.apache.batik.transcoder.keys.BooleanKey;
import org.apache.batik.transcoder.keys.PaintKey;
import org.w3c.dom.Document;


This class enables to transcode an input to an image of any format.

Two transcoding hints (KEY_WIDTH and
KEY_HEIGHT) can be used to respectively specify the image
width and the image height. If only one of these keys is specified,
the transcoder preserves the aspect ratio of the original image.

The KEY_BACKGROUND_COLOR defines the background color
to use for opaque image formats, or the background color that may
be used for image formats that support alpha channel.

The KEY_AOI represents the area of interest to paint
in device space.

Three additional transcoding hints that act on the SVG
processor can be specified:

KEY_LANGUAGE to set the default language to use (may be
used by a <switch> SVG element for example),
KEY_USER_STYLESHEET_URI to fix the URI of a user
stylesheet, and KEY_MM_PER_PIXEL to specify the number of
millimeters in each pixel .

Author:Thierry Kormann
Version:$Id: ImageTranscoder.java 1805419 2017-08-18 13:04:30Z ssteiner $
/**
 * This class enables to transcode an input to an image of any format.
 *
 * <p>Two transcoding hints (<code>KEY_WIDTH</code> and
 * <code>KEY_HEIGHT</code>) can be used to respectively specify the image
 * width and the image height. If only one of these keys is specified,
 * the transcoder preserves the aspect ratio of the original image.
 *
 * <p>The <code>KEY_BACKGROUND_COLOR</code> defines the background color
 * to use for opaque image formats, or the background color that may
 * be used for image formats that support alpha channel.
 *
 * <p>The <code>KEY_AOI</code> represents the area of interest to paint
 * in device space.
 *
 * <p>Three additional transcoding hints that act on the SVG
 * processor can be specified:
 *
 * <p><code>KEY_LANGUAGE</code> to set the default language to use (may be
 * used by a &lt;switch&gt; SVG element for example),
 * <code>KEY_USER_STYLESHEET_URI</code> to fix the URI of a user
 * stylesheet, and <code>KEY_MM_PER_PIXEL</code> to specify the number of
 * millimeters in each pixel .
 *
 * @author <a href="mailto:Thierry.Kormann@sophia.inria.fr">Thierry Kormann</a>
 * @version $Id: ImageTranscoder.java 1805419 2017-08-18 13:04:30Z ssteiner $
 */
public abstract class ImageTranscoder extends SVGAbstractTranscoder {

    
Constructs a new ImageTranscoder.

/**
     * Constructs a new <code>ImageTranscoder</code>.
     */
    protected ImageTranscoder() {
    }

    
Transcodes the specified Document as an image in the specified output.

Params:
  • document – the document to transcode
  • uri – the uri of the document or null if any
  • output – the ouput where to transcode
Throws:
/**
     * Transcodes the specified Document as an image in the specified output.
     *
     * @param document the document to transcode
     * @param uri the uri of the document or null if any
     * @param output the ouput where to transcode
     * @exception TranscoderException if an error occured while transcoding
     */
    protected void transcode(Document document,
                             String uri,
                             TranscoderOutput output)
            throws TranscoderException {

        // Sets up root, curTxf & curAoi
        super.transcode(document, uri, output);

        // prepare the image to be painted
        int w = (int)(width+0.5);
        int h = (int)(height+0.5);

        // paint the SVG document using the bridge package
        // create the appropriate renderer
        ImageRenderer renderer = createRenderer();
        renderer.updateOffScreen(w, h);
        // curTxf.translate(0.5, 0.5);
        renderer.setTransform(curTxf);
        renderer.setTree(this.root);
        this.root = null; // We're done with it...

        try {
            // now we are sure that the aoi is the image size
            Shape raoi = new Rectangle2D.Float(0, 0, width, height);
            // Warning: the renderer's AOI must be in user space
            renderer.repaint(curTxf.createInverse().
                             createTransformedShape(raoi));
            BufferedImage rend = renderer.getOffScreen();
            renderer = null; // We're done with it...

            BufferedImage dest = createImage(w, h);

            Graphics2D g2d = GraphicsUtil.createGraphics(dest);
            if (hints.containsKey(KEY_BACKGROUND_COLOR)) {
                Paint bgcolor = (Paint)hints.get(KEY_BACKGROUND_COLOR);
                g2d.setComposite(AlphaComposite.SrcOver);
                g2d.setPaint(bgcolor);
                g2d.fillRect(0, 0, w, h);
            }
            if (rend != null) { // might be null if the svg document is empty
                g2d.drawRenderedImage(rend, new AffineTransform());
            }
            g2d.dispose();
            rend = null; // We're done with it...
            writeImage(dest, output);
        } catch (Exception ex) {
            throw new TranscoderException(ex);
        }
    }

    
Method so subclasses can modify the Renderer used to render document.

/**
     * Method so subclasses can modify the Renderer used to render document.
     */
    protected ImageRenderer createRenderer() {
        ImageRendererFactory rendFactory = new ConcreteImageRendererFactory();
        // ImageRenderer renderer = rendFactory.createDynamicImageRenderer();
        return rendFactory.createStaticImageRenderer();
    }

    
Converts an image so that viewers which do not support the
alpha channel will see a white background (and not a black
one).

Params:
  • img – the image to convert
  • sppsm – 
/**
     * Converts an image so that viewers which do not support the
     * alpha channel will see a white background (and not a black
     * one).
     * @param img the image to convert
     * @param sppsm
     */
    protected void forceTransparentWhite(BufferedImage img, SinglePixelPackedSampleModel sppsm) {
        //
        // This is a trick so that viewers which do not support
        // the alpha channel will see a white background (and not
        // a black one).
        //
        int w = img.getWidth();
        int h = img.getHeight();
        DataBufferInt biDB=(DataBufferInt)img.getRaster().getDataBuffer();
        int scanStride = sppsm.getScanlineStride();
        int dbOffset = biDB.getOffset();
        int[] pixels = biDB.getBankData()[0];
        int p = dbOffset;
        int adjust = scanStride - w;
        int a=0, r=0, g=0, b=0, pel=0;
        for(int i=0; i<h; i++){
            for(int j=0; j<w; j++){
                pel = pixels[p];
                a = (pel >> 24) & 0xff;
                r = (pel >> 16) & 0xff;
                g = (pel >> 8 ) & 0xff;
                b =  pel        & 0xff;
                r = (255*(255 -a) + a*r)/255;
                g = (255*(255 -a) + a*g)/255;
                b = (255*(255 -a) + a*b)/255;
                pixels[p++] =
                    (a<<24 & 0xff000000) |
                    (r<<16 & 0xff0000) |
                    (g<<8  & 0xff00) |
                    (b     & 0xff);
            }
            p += adjust;
        }
    }

    
Creates a new image with the specified dimension.

Params:
  • width – the image width in pixels
  • height – the image height in pixels
/**
     * Creates a new image with the specified dimension.
     * @param width the image width in pixels
     * @param height the image height in pixels
     */
    public abstract BufferedImage createImage(int width, int height);

    
Writes the specified image to the specified output.

Params:
  • img – the image to write
  • output – the output where to store the image
Throws:
/**
     * Writes the specified image to the specified output.
     * @param img the image to write
     * @param output the output where to store the image
     * @throws TranscoderException if an error occured while storing the image
     */
    public abstract void writeImage(BufferedImage img, TranscoderOutput output)
        throws TranscoderException;

    // --------------------------------------------------------------------
    // Keys definition
    // --------------------------------------------------------------------

    
The image background paint key.


  

    Key:
    KEY_BACKGROUND_COLOR
  

  

    Value:
    Paint
  

  

    Default:
    null
  

  

    Required:
    No
  

  

    Description:
    Specify the background color to use.
      The color is required by opaque image formats and is used by
      image formats that support alpha channel.
  




/**
     * The image background paint key.
     * <table summary="" border="0" cellspacing="0" cellpadding="1">
     *   <tr>
     *     <th valign="top" align="right">Key:</th>
     *     <td valign="top">KEY_BACKGROUND_COLOR</td>
     *   </tr>
     *   <tr>
     *     <th valign="top" align="right">Value:</th>
     *     <td valign="top">Paint</td>
     *   </tr>
     *   <tr>
     *     <th valign="top" align="right">Default:</th>
     *     <td valign="top">null</td>
     *   </tr>
     *   <tr>
     *     <th valign="top" align="right">Required:</th>
     *     <td valign="top">No</td>
     *   </tr>
     *   <tr>
     *     <th valign="top" align="right">Description:</th>
     *     <td valign="top">Specify the background color to use.
     *       The color is required by opaque image formats and is used by
     *       image formats that support alpha channel.</td>
     *   </tr>
     * </table>
     */
    public static final TranscodingHints.Key KEY_BACKGROUND_COLOR
        = new PaintKey();

    
The forceTransparentWhite key.


  

    Key:
    KEY_FORCE_TRANSPARENT_WHITE
  

  

    Value:
    Boolean
  

  

    Default:
    false
  

  

    Required:
    No
  

  

    Description:
    It controls whether the encoder should force
      the image's fully transparent pixels to be fully transparent
      white instead of fully transparent black.  This is useful when
      the encoded file is displayed in a browser which does not
      support transparency correctly and lets the image display with
      a white background instead of a black background.
      

      However, note that the modified image will display differently
      over a white background in a viewer that supports
      transparency.
      

      Not all Transcoders use this key (in particular some formats
      can't preserve the alpha channel at all in which case this
      is not used).		
  




/**
     * The forceTransparentWhite key.
     *
     * <table summary="" border="0" cellspacing="0" cellpadding="1">
     *   <tr>
     *     <th valign="top" align="right">Key:</th>
     *     <td valign="top">KEY_FORCE_TRANSPARENT_WHITE</td>
     *   </tr>
     *   <tr>
     *     <th valign="top" align="right">Value:</th>
     *     <td valign="top">Boolean</td>
     *   </tr>
     *   <tr>
     *     <th valign="top" align="right">Default:</th>
     *     <td valign="top">false</td>
     *   </tr>
     *   <tr>
     *     <th valign="top" align="right">Required:</th>
     *     <td valign="top">No</td>
     *   </tr>
     *   <tr>
     *     <th valign="top" align="right">Description:</th>
     *     <td valign="top">It controls whether the encoder should force
     *       the image's fully transparent pixels to be fully transparent
     *       white instead of fully transparent black.  This is useful when
     *       the encoded file is displayed in a browser which does not
     *       support transparency correctly and lets the image display with
     *       a white background instead of a black background.
     *       <br>
     *       However, note that the modified image will display differently
     *       over a white background in a viewer that supports
     *       transparency.
     *       <br>
     *       Not all Transcoders use this key (in particular some formats
     *       can't preserve the alpha channel at all in which case this
     *       is not used).</td>
     *   </tr>
     * </table>
     */
    public static final TranscodingHints.Key KEY_FORCE_TRANSPARENT_WHITE
        = new BooleanKey();
}