Utility classes for transforming arbitrary SVG elements with Batik. Read more: http://comfreek.blogspot.com/2014/06/batik-how-to-transform-arbitrary-svg.html

Transformation of arbitrary SVG elements with Batik

.

AffineTransformUtils.java

package com.github.comfreek.util;

import java.awt.geom.AffineTransform;

/**
 * Utility class.<br>
 * Its primary intent is to provide {@link #affineTransformToString(AffineTransform) affineTransformToString()}.
 * 
 * @author ComFreek <comfreek@outlook.com> if not otherwise noted.
 * @license MIT (for all parts whose author is ComFreek)
 */
public class AffineTransformUtils {

    private AffineTransformUtils() {
    }

    /**
     * Converts an AffineTransform to a "matrix(...)" string representation as
     * used in SVG files for the "transform" attribute.
     *
     * @see <a
     * href="http://www.w3.org/TR/SVG11/coords.html#TransformAttribute">W3C SVG
     * 1.1 Specification: The 'transform' attribute</a>
     * @see <a
     * href="https://developer.mozilla.org/en/docs/Web/SVG/Attribute/transform">Mozilla
     * Developer Network: SVG transforma attribute</a>
     *
     * @author Jonathan Wood in a mail to the xmlgraphics-batik-users mailing list: <a href="http://mail-archives.apache.org/mod_mbox/xmlgraphics-batik-users/201208.mbox/%3cCAKiJDQTpJE-4hEGG-QMn=cDXK2tAn5H52TWBCZJxZ30pf15DYQ@mail.gmail.com%3e">click here</a>
     *
     * @param at The AffineTransform object
     * @return Returns a "matrix(...)" string representation. for more
     * information
     */
    public static String affineTransformToString(final AffineTransform at) {
        double[] matrix = {0.0, 0.0, 0.0, 0.0, 0.0, 0.0};
        at.getMatrix(matrix);
        return matrixArrayToString(matrix);
    }

    /**
     * Converts a double array in the form of {a, b, c, d, e, f} to a string
     * representation in the form of "matrix(a b c d e f)".
     *
     * The returned string can be used in transform attributes of elements in
     * SVG files. files.
     *
     * @see AffineTransformUtils#affineTransformToString(AffineTransform)
     * @see <a
     * href="http://www.w3.org/TR/SVG11/coords.html#TransformAttribute">W3C SVG
     * 1.1 Specification: The 'transform' attribute</a>
     * @see <a
     * href="https://developer.mozilla.org/en/docs/Web/SVG/Attribute/transform">Mozilla
     * Developer Network: SVG transforma attribute</a>
     *
     * @author Jonathan Wood in a mail to the xmlgraphics-batik-users mailing list: <a href="http://mail-archives.apache.org/mod_mbox/xmlgraphics-batik-users/201208.mbox/%3cCAKiJDQTpJE-4hEGG-QMn=cDXK2tAn5H52TWBCZJxZ30pf15DYQ@mail.gmail.com%3e">click here</a>
     *
     * @param vals A double array a
     * @return Returns the string representation in the form of "matrix(a b c d e f)".
     */
    public static String matrixArrayToString(double[] vals) {
        return new StringBuilder("matrix(").append(vals[0]).append(" ").append(vals[1]).append(" ").append(vals[2]).append(" ").append(vals[3]).append(" ").append(vals[4]).append(" ").append(vals[5]).append(") ").toString();
    }
}

SVGUtils.java

package com.github.comfreek.util;

import java.awt.geom.AffineTransform;
import org.apache.batik.parser.AWTTransformProducer;
import org.apache.batik.parser.TransformListParser;
import org.apache.batik.util.SVGConstants;
import org.w3c.dom.Element;

/**
 * This class provides static utility methods for the use with Batik and SVG
 * elements.
 * 
 * @author ComFreek <comfreek@outlook.com> if not otherwise noted.
 * @license MIT (for all parts whose author is ComFreek)
 */
public class SVGUtils {

    private SVGUtils() {
    }

    /**
     * Applies an AffineTransform to a (SVG) element.
     * <br>
     * While this function works with all classes equal to or subclassing
     * {@link org.w3c.dom.Element Element}, adding and modifying the "transform"
     * attribute is probably of no effect.
     * <br>
     * Example:
     * <pre>
     * <code>  // Document svgDoc = ...;
     *   Element elem = svgDoc.getElementById("your-id");
     *   AffineTransform translateBy5Units =
     *       AffineTransform.getTranslateInstance(5, 0);
     *   transformElement(elem, translateBy5Units);
     *
     *   AffineTransform scaleByFactor10 =
     *       AffineTransform.getScaleInstance(10, 10);
     *   transformElement(elem, scaleByFactor10);
     * </code>
     * </pre>
     *
     * @see #getElementTransform(Element)
     *
     * @param element The element.
     * @param transform The AffineTransform you want to apply. The resulting
     * transformation of the object is
     * <code>transform.{@link AffineTransform#concatenate(AffineTransform) concatenated}(oldTransform)</code>,
     * where <code>oldTransform</code> represents the current local (i.e.
     * possible parents' transforms will not be taken into acconut) transform of
     * the element.
     */
    public static void transformElement(final Element element, final AffineTransform transform) {
        final AffineTransform oldTransform = getElementTransform(element);
        transform.concatenate(oldTransform);
        element.setAttributeNS(null, SVGConstants.SVG_TRANSFORM_ATTRIBUTE,
                AffineTransformUtils.affineTransformToString(transform));
    }

    /**
     * Retrieves and parses the transformation attribute of a Element into an
     * AffineTransform object.
     * <br>
     *
     * This function can cope with all transform values supported by
     * {@link org.apache.batik.parser.TransformListParser TransformListParser}.
     * These include <code>translate()</code>, <code>rotate()</code>,
     * <code>scale()</code>, <code>skew()</code> and <code>matrix()</code>. It
     * will also correctly handle empty or non-existing attributes (i.e.
     * returning an Identity matrix).
     *
     * @see #transformElement(Element, AffineTransform)
     *
     * @author fireball in a mail to the xmlgraphics-batik-users mailing list:
     * <a href="http://mail-archives.apache.org/mod_mbox/xmlgraphics-batik-users/201208.mbox/%3c1344872547972-4655199.post@n4.nabble.com%3e">click here</a>
     *
     * @param element The SVG element.
     * @return An AffineTransform which equals the (local) transformations
     * specified in the SVG element.
     */
    public static AffineTransform getElementTransform(final Element element) {
        final String oldTransformStr = element.getAttributeNS(null, SVGConstants.SVG_TRANSFORM_ATTRIBUTE);
        final TransformListParser tListParser = new TransformListParser();
        final AWTTransformProducer tProducer = new AWTTransformProducer();

        tListParser.setTransformListHandler(tProducer);
        tListParser.parse(oldTransformStr);
        return tProducer.getAffineTransform();
    }
}

UsageExample.java

// Consult Batik's documentation or Google if you don't
// know how to load a document.
// Document svgDoc = ...;
Element elem = svgDoc.getElementById("your-id");
AffineTransform translateBy5Units =
		AffineTransform.getTranslateInstance(5, 0);
transformElement(elem, translateBy5Units);

AffineTransform scaleByFactor10 =
		AffineTransform.getScaleInstance(10, 10);
transformElement(elem, scaleByFactor10);