如何以编程方式在 SVG 文件中进行组转换？

Question

我有包含以下图像的 SVG 文件：

每个箭头都由这样的代码表示：

<g
   transform="matrix(-1,0,0,-1,149.82549,457.2455)"
   id="signS"
   inkscape:label="#sign">
  <title
     id="title4249">South, 180</title>
  <path
     sodipodi:nodetypes="ccc"
     inkscape:connector-curvature="0"
     id="path4251"
     d="m 30.022973,250.04026 4.965804,-2.91109 4.988905,2.91109"
     style="fill:none;fill-rule:evenodd;stroke:#000000;stroke-width:0.6855976px;stroke-linecap:butt;stroke-linejoin:miter;stroke-opacity:1" />
  <rect
     y="250.11305"
     x="29.768578"
     height="2.6057031"
     width="10.105703"
     id="rect4253"
     style="fill:#008000;fill-opacity:1;stroke:#000000;stroke-width:0.53715414;stroke-opacity:1" />
</g>

我想计算矩形（rect节点）的绝对位置。为此，我需要评估 g 标签（上例中的 matrix(-1,0,0,-1,149.82549,457.2455)）的 transform 标签内的表达式。

我该怎么做？

我假设第一步是使用 Apache Batik:

将文件读取为 SVGDocument

import java.io.IOException;

import org.apache.batik.dom.svg.SAXSVGDocumentFactory;
import org.apache.batik.util.XMLResourceDescriptor;

import org.w3c.dom.Document;

try {
    String parser = XMLResourceDescriptor.getXMLParserClassName();
    SAXSVGDocumentFactory f = new SAXSVGDocumentFactory(parser);
    String uri = "http://www.example.org/diagram.svg";
    Document doc = f.createDocument(uri);
} catch (IOException ex) {
    // ...
}

据我所知，doc可以转换为SVGDocument。

如何从 SVG 文档获取矩形或组的绝对位置？

注意：我需要一些 现有的 代码来执行上述转换（不要让我自己实现这些转换 - 它们必须已经实现，我想重新- 使用该代码）。

更新 1（08.11.2015 12:56 MSK）：

首次尝试实施 Robert Longson 的建议：

public final class BatikTest {
    @Test
    public void test() throws XPathExpressionException {
        try {
            final File initialFile =
                new File("src/main/resources/trailer/scene05_signs.svg");
            InputStream sceneFileStream = Files.asByteSource(initialFile).openStream();


            String parser = XMLResourceDescriptor.getXMLParserClassName();
            SAXSVGDocumentFactory f = new SAXSVGDocumentFactory(parser);
            String uri = "http://www.example.org/diagram.svg";
            final SVGOMDocument doc = (SVGOMDocument) f.createDocument(
                uri, sceneFileStream);

            final NodeList nodes =
                doc.getDocumentElement().getElementsByTagName("g");
            SVGOMGElement signSouth = null;


            for (int i=0; (i < nodes.getLength()) && (signSouth == null); i++) {
                final Node curNode = nodes.item(i);
                final Node id = curNode.getAttributes().getNamedItem("id");
                if ("signS".equals(id.getTextContent())) {
                    signSouth = (SVGOMGElement) curNode;
                }

                System.out.println("curNode: " + nodes);
            }
            System.out.println("signSouth: " + signSouth);

            final NodeList rectNodes = signSouth.getElementsByTagName("rect");
            System.out.println("rectNodes: " + rectNodes);

            SVGOMRectElement rectNode = (SVGOMRectElement) rectNodes.item(0);

            System.out.println("rectNode: " + rectNode);

            final SVGMatrix m2 =
                signSouth.getTransformToElement(rectNode);

            System.out.println("m2: " + m2);
        } catch (IOException ex) {
            Assert.fail(ex.getMessage());
        }
    }
}

对 m2.getA()-m2.getF() 的调用导致 NullPointerException 秒。

更新 2（08.11.2015 13:38 MSK）：

添加了以下代码来创建 SVGPoint 并对其应用矩阵变换：

final SVGSVGElement docElem = (SVGSVGElement)
    doc.getDocumentElement();
final SVGPoint svgPoint = docElem.createSVGPoint();
svgPoint.setX((float) x);
svgPoint.setY((float) y);
final SVGPoint svgPoint1 =
    svgPoint.matrixTransform(signSouth.getScreenCTM()); // Line 77

System.out.println("x: " + svgPoint1.getX());
System.out.println("y: " + svgPoint1.getY());

结果：

java.lang.NullPointerException
    at org.apache.batik.dom.svg.SVGLocatableSupport.getAffineTransform(Unknown Source)
    at org.apache.batik.dom.svg.AbstractSVGMatrix.getA(Unknown Source)
    at org.apache.batik.dom.svg.SVGOMPoint.matrixTransform(Unknown Source)
    at org.apache.batik.dom.svg.SVGOMPoint.matrixTransform(Unknown Source)
    at [...].BatikTest.test(BatikTest.java:77)

更新 3，赏金条款 (10.11.2015 MSK)：

获得赏金必须满足的条件：

我会将赏金奖励给在 JUnit 测试 BatikTest 中设法实现方法 magicallyCalculateXCoordinate 和 magicallyCalculateYCoordinate 的男女主角，这样我就可以在我的 Java 编码 InkScape 中显示的形状的坐标（示例请参见以下屏幕截图）。

计算 SVG 文件中形状位置的方法必须有效

对于组节点（如图片和 sample file 中的节点）或
三角形。

您提供的代码必须适用于示例文件中的所有四种形状，即。 e.使用它我必须能够在 Java 代码中计算出它们的坐标，这与 Inkscape 中显示的坐标相同。

您可以向方法 magicallyCalculateXCoordinate 和 magicallyCalculateYCoordinate 添加参数，您也可以创建自己的方法来计算坐标。

您可以使用任何可合法用于商业目的的库。

与此请求相关的所有文件都可以在 GitHub 上找到。我设法使用 IntelliJ Idea Community Edition 14.1.5 编译测试。

Answer 1

我知道，我来晚了，但我偶然发现了这个问题并且很喜欢这个谜语 ;-)

svg 中的原点是左上角，而 inkscape 中的原点是左下角。

所以我们需要应用描边和变换，然后找到左下角的点四舍五入到三位小数。我使用 GVTBuilder 获取应用样式的边界框，然后转换 boundingBox，请求转换组的边界框，然后使用 xMin 和 yMax 作为参考点。使用 viewbox 确定高度，我转换了 y 坐标，最后对坐标进行了四舍五入。（请参阅 github 上的拉取请求）

package test.java.svgspike;

import org.apache.batik.anim.dom.SAXSVGDocumentFactory;
import org.apache.batik.anim.dom.SVGOMDocument;
import org.apache.batik.anim.dom.SVGOMGElement;
import org.apache.batik.bridge.BridgeContext;
import org.apache.batik.bridge.GVTBuilder;
import org.apache.batik.bridge.UserAgentAdapter;
import org.apache.batik.gvt.GraphicsNode;
import org.apache.batik.util.XMLResourceDescriptor;

import javax.xml.xpath.XPathExpressionException;

import java.awt.geom.Point2D;
import java.awt.geom.Path2D;
import java.awt.geom.Rectangle2D;
import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.math.BigDecimal;

import com.google.common.io.Files;

import org.junit.Assert;
import org.junit.Test;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;

/**
 * Created by pisarenko on 10.11.2015.
 */
public final class BatikTest {

    @Test
    public void test() throws XPathExpressionException {
        try {
            final File initialFile =
                    new File("src/test/resources/scene05_signs.svg");
            InputStream sceneFileStream = Files.asByteSource(initialFile).openStream();

            String parser = XMLResourceDescriptor.getXMLParserClassName();
            SAXSVGDocumentFactory f = new SAXSVGDocumentFactory(parser);
            String uri = "http://www.example.org/diagram.svg";
            final SVGOMDocument doc = (SVGOMDocument) f.createDocument(
                    uri, sceneFileStream);

            String viewBox = doc.getDocumentElement().getAttribute("viewBox");

            Point2D referencePoint = getReferencePoint(doc, getGroupElement(doc, "signS"));

            double signSouthX = magicallyCalculateXCoordinate(referencePoint);
            double signSouthY = magicallyCalculateYCoordinate(referencePoint, viewBox);

            Assert.assertEquals(109.675, signSouthX, 0.0000001);
            Assert.assertEquals(533.581, signSouthY, 0.0000001);

            referencePoint = getReferencePoint(doc, getGroupElement(doc, "signN"));
            Assert.assertEquals(109.906, magicallyCalculateXCoordinate(referencePoint), 0.0000001);
            Assert.assertEquals(578.293, magicallyCalculateYCoordinate(referencePoint, viewBox), 0.0000001);

            referencePoint = getReferencePoint(doc, getGroupElement(doc, "signE"));
            Assert.assertEquals(129.672, magicallyCalculateXCoordinate(referencePoint), 0.0000001);
            Assert.assertEquals(554.077, magicallyCalculateYCoordinate(referencePoint, viewBox), 0.0000001);

            referencePoint = getReferencePoint(doc, getGroupElement(doc, "signW"));
            Assert.assertEquals(93.398, magicallyCalculateXCoordinate(referencePoint), 0.0000001);
            Assert.assertEquals(553.833, magicallyCalculateYCoordinate(referencePoint, viewBox), 0.0000001);


        } catch (IOException ex) {
            Assert.fail(ex.getMessage());
        }
    }

    private SVGOMGElement getGroupElement(SVGOMDocument doc, String id){
        final NodeList nodes = doc.getDocumentElement().getElementsByTagName("g");
        SVGOMGElement signGroup = null;
        for (int i=0; (i < nodes.getLength()) && (signGroup == null); i++) {
            final Node curNode = nodes.item(i);
            final Node idNode = curNode.getAttributes().getNamedItem("id");
            if (id.equals(idNode.getTextContent())) signGroup = (SVGOMGElement) curNode;
        }
        return signGroup;
    }

    /**
     * @param doc
     * @param signGroup
     * @return the reference point, inkscape uses for group (bottom left corner of group)
     */
    private Point2D getReferencePoint(SVGOMDocument doc, SVGOMGElement signGroup){

        Point2D referencePoint = new Point2D.Double(0, 0);

        try {

            BridgeContext ctx = new BridgeContext(new UserAgentAdapter());
            new GVTBuilder().build(ctx, doc);
            GraphicsNode gvtElement = new GVTBuilder().build(ctx, signGroup);

            Rectangle2D rc = gvtElement.getSensitiveBounds();
            rc = ((Path2D) gvtElement.getTransform().createTransformedShape(rc)).getBounds2D();

          //find xMin and yMax in poi
            referencePoint = new Point2D.Double(rc.getMinX(), rc.getMaxY());

        } catch (Exception e) {
            e.printStackTrace();
        }
        return referencePoint;
    }

    /**
     * inkscape states y coordinate with origin in left bottom corner, while svg uses top left corner as origin
     * @param referencePoint bottom left corner of group
     * @param viewBox in "originX originY width height" notation
     * @return corrected y coordinate, rounded to three decimal figures (half up)
     */
    private double magicallyCalculateYCoordinate(Point2D referencePoint, String viewBox) {
        String[] viewBoxValues = viewBox.split(" ");
        BigDecimal roundedY = new BigDecimal(Double.parseDouble(viewBoxValues[3])-referencePoint.getY());
        roundedY = roundedY.setScale(3, BigDecimal.ROUND_HALF_UP);
        return roundedY.doubleValue();
    }

    /**
     * @param referencePoint bottom left corner of group
     * @return x coordinate, rounded to three decimal figures (half up)
     */
    private double magicallyCalculateXCoordinate(Point2D referencePoint) {
        BigDecimal roundedX = new BigDecimal(referencePoint.getX()).setScale(3, BigDecimal.ROUND_HALF_UP);
        return roundedX.doubleValue();
    }

}

它应该适用于所有组和所有转换。

如何以编程方式在 SVG 文件中进行组转换？

How to do the group transforms in SVG file programmatically?

java

svg

batik