有相關的閱讀懸而未決的問題數量和解析SVG路徑：如何加載和分析SVG文件
此問題的答案旨在解決所有這些問題。
問題的SVG path元素包含一個data attribute（d）。有時需要從SVG文件中加載，解析和提取路徑信息。
你怎麼加載，解析和提取使用Java的SVG文件SVG路徑信息？使用Apache Batik
加載並解析SVG文件。該解決方案顯示了將SVG文件轉換爲MetaPost的初步階段的Java代碼。這應該爲如何使用Java加載，解析和提取SVG文件中的內容提供一個總體思路。
您需要以下庫：
batik-anim.jar
batik-awt-util.jar
batik-bridge.jar
batik-css.jar
batik-dom.jar
batik-ext.jar
batik-gvt.jar
batik-parser.jar
batik-script.jar
batik-svg-dom.jar
batik-svggen.jar
batik-util.jar
batik-xml.jar
xml-apis-ext.jar
主要應用加載SVG文件到DOM，然後轉換DOM到SVG DOM。方法調用initSVGDOM()非常重要。在不調用initSVGDOM()的情況下，從DOM中提取SVG DOM元素的方法將不可用。
import java.io.File;
import java.io.IOException;
import java.net.URI;
import org.apache.batik.bridge.BridgeContext;
import org.apache.batik.bridge.DocumentLoader;
import org.apache.batik.bridge.GVTBuilder;
import org.apache.batik.bridge.UserAgent;
import org.apache.batik.bridge.UserAgentAdapter;
import org.apache.batik.dom.svg.SAXSVGDocumentFactory;
import org.apache.batik.dom.svg.SVGOMSVGElement;
import org.apache.batik.util.XMLResourceDescriptor;
import org.w3c.dom.Document;
import org.w3c.dom.NodeList;
/**
* Responsible for converting all SVG path elements into MetaPost curves.
*/
public class SVGMetaPost {
private static final String PATH_ELEMENT_NAME = "path";
private Document svgDocument;
/**
* Creates an SVG Document given a URI.
*
* @param uri Path to the file.
* @throws Exception Something went wrong parsing the SVG file.
*/
public SVGMetaPost(String uri) throws IOException {
setSVGDocument(createSVGDocument(uri));
}
/**
* Finds all the path nodes and converts them to MetaPost code.
*/
public void run() {
NodeList pathNodes = getPathElements();
int pathNodeCount = pathNodes.getLength();
for(int iPathNode = 0; iPathNode < pathNodeCount; iPathNode++) {
MetaPostPath mpp = new MetaPostPath(pathNodes.item(iPathNode));
System.out.println(mpp.toCode());
}
}
/**
* Returns a list of elements in the SVG document with names that
* match PATH_ELEMENT_NAME.
*
* @return The list of "path" elements in the SVG document.
*/
private NodeList getPathElements() {
return getSVGDocumentRoot().getElementsByTagName(PATH_ELEMENT_NAME);
}
/**
* Returns an SVGOMSVGElement that is the document's root element.
*
* @return The SVG document typecast into an SVGOMSVGElement.
*/
private SVGOMSVGElement getSVGDocumentRoot() {
return (SVGOMSVGElement)getSVGDocument().getDocumentElement();
}
/**
* This will set the document to parse. This method also initializes
* the SVG DOM enhancements, which are necessary to perform SVG and CSS
* manipulations. The initialization is also required to extract information
* from the SVG path elements.
*
* @param document The document that contains SVG content.
*/
public void setSVGDocument(Document document) {
initSVGDOM(document);
this.svgDocument = document;
}
/**
* Returns the SVG document parsed upon instantiating this class.
*
* @return A valid, parsed, non-null SVG document instance.
*/
public Document getSVGDocument() {
return this.svgDocument;
}
/**
* Enhance the SVG DOM for the given document to provide CSS- and SVG-specific
* DOM interfaces.
*
* @param document The document to enhance.
* @link http://wiki.apache.org/xmlgraphics-batik/BootSvgAndCssDom
*/
private void initSVGDOM(Document document) {
UserAgent userAgent = new UserAgentAdapter();
DocumentLoader loader = new DocumentLoader(userAgent);
BridgeContext bridgeContext = new BridgeContext(userAgent, loader);
bridgeContext.setDynamicState(BridgeContext.DYNAMIC);
// Enable CSS- and SVG-specific enhancements.
(new GVTBuilder()).build(bridgeContext, document);
}
/**
* Use the SAXSVGDocumentFactory to parse the given URI into a DOM.
*
* @param uri The path to the SVG file to read.
* @return A Document instance that represents the SVG file.
* @throws Exception The file could not be read.
*/
private Document createSVGDocument(String uri) throws IOException {
String parser = XMLResourceDescriptor.getXMLParserClassName();
SAXSVGDocumentFactory factory = new SAXSVGDocumentFactory(parser);
return factory.createDocument(uri);
}
/**
* Reads a file and parses the path elements.
*
* @param args args[0] - Filename to parse.
* @throws IOException Error reading the SVG file.
*/
public static void main(String args[]) throws IOException {
URI uri = new File(args[0]).toURI();
SVGMetaPost converter = new SVGMetaPost(uri.toString());
converter.run();
}
}
注：調用initSVGDOM()應該是，除非另有規定蠟染的默認行爲。唉，它不是，並且發現這顆寶石意味着在他們的網站上閱讀documentation buried。
解析SVG DOM然後是相對平凡的。該toCode()方法是類的主力：
import org.apache.batik.dom.svg.SVGItem;
import org.apache.batik.dom.svg.SVGOMPathElement;
import org.w3c.dom.Node;
import org.w3c.dom.svg.SVGPathSegList;
/**
* Responsible for converting an SVG path element to MetaPost. This
* will convert just the bezier curve portion of the path element, not
* its style. Typically the SVG path data is provided from the "d" attribute
* of an SVG path node.
*/
public class MetaPostPath extends MetaPost {
private SVGOMPathElement pathElement;
/**
* Use to create an instance of a class that can parse an SVG path
* element to produce MetaPost code.
*
* @param pathNode The path node containing a "d" attribute (output as MetaPost code).
*/
public MetaPostPath(Node pathNode) {
setPathNode(pathNode);
}
/**
* Converts this object's SVG path to a MetaPost draw statement.
*
* @return A string that represents the MetaPost code for a path element.
*/
public String toCode() {
StringBuilder sb = new StringBuilder(16384);
SVGOMPathElement pathElement = getPathElement();
SVGPathSegList pathList = pathElement.getNormalizedPathSegList();
int pathObjects = pathList.getNumberOfItems();
sb.append((new MetaPostComment(getId())).toString());
for(int i = 0; i < pathObjects; i++) {
SVGItem item = (SVGItem)pathList.getItem(i);
sb.append(String.format("%s%n", item.getValueAsString()));
}
return sb.toString();
}
/**
* Returns the value for the id attribute of the path element. If the
* id isn't present, this will probably throw a NullPointerException.
*
* @return A non-null, but possibly empty String.
*/
private String getId() {
return getPathElement().getAttributes().getNamedItem("id").getNodeValue();
}
/**
* Typecasts the given pathNode to an SVGOMPathElement for later analysis.
*
* @param pathNode The path element that contains curves, lines, and other
* SVG instructions.
*/
private void setPathNode(Node pathNode) {
this.pathElement = (SVGOMPathElement)pathNode;
}
/**
* Returns an SVG document element that contains path instructions (usually
* for drawing on a canvas).
*
* @return An object that contains a list of items representing pen
* movements.
*/
private SVGOMPathElement getPathElement() {
return this.pathElement;
}
}
編譯將從環境而異環境。類似如下的腳本應該有所幫助：
#!/bin/bash
mkdir -p ./build
javac -cp ./lib/* -d ./build ./source/*.java
務必把所有的.jar文件到./lib目錄。將源文件放入./source目錄中。
創建一個腳本（或批處理文件）來執行該程序：
#!/bin/bash
java -cp ./lib/*:./build SVGMetaPost $1
當針對包含有效SVG路徑的文件運行，這產生：
$ ./run.sh stripe/trigon.svg
% path8078-6
M 864.1712 779.3069
C 864.1712 779.3069 868.04065 815.6211 871.4032 833.4621
C 873.4048 844.08203 874.91724 855.0544 879.0846 864.82227
C 884.24023 876.9065 895.2377 887.9899 900.0184 897.3661
C 904.7991 906.7422 907.3466 918.3257 907.3466 918.3257
C 907.3466 918.3257 892.80817 887.6536 864.1712 887.3086
C 835.53424 886.9637 820.9958 918.3257 820.9958 918.3257
C 820.9958 918.3257 823.6176 906.59644 828.32404 897.3661
C 833.0304 888.1356 844.10223 876.9065 849.2578 864.82227
C 853.4252 855.05444 854.9376 844.08203 856.93915 833.4621
C 860.3017 815.6211 864.17114 779.3069 864.17114 779.3069
z
從這裏應該清楚如何將SVG路徑數據讀入它們的corr使用Java來支持SVG對象。
需要注意的是最簡單的方法來從SVG轉換爲MetaPost是：
pstoedit將PDF轉換爲MetaPost。