Easiest way to read in svg path data with Java?

Question

I'm looking to consume an svg image and parse/process the different paths to do a custom conversion. What is the easiest way, in Java, to simply extract the path data? I was looking at the apache xmlgraphics/batik packages, but it's not real obvious how to return the path types and parameters. Any suggestions?

Answer 1

To simply extract the path data you can use XPath.

Suppose you have this SVG and you want to extract all the path data (from both path elements):

<svg>
  <rect x="1" y="1" width="1198" height="598"
        fill="none" stroke="blue" stroke-width="1" />

  <path d="M200,300 Q400,50 600,300 T1000,300"
        fill="none" stroke="red" stroke-width="5"  />
  <g fill="black" >
    <circle cx="200" cy="300" r="10"/>
    <circle cx="600" cy="300" r="10"/>
    <circle cx="1000" cy="300" r="10"/>
  </g>
  <g fill="#888888" >
    <circle cx="400" cy="50" r="10"/>
    <circle cx="800" cy="550" r="10"/>
  </g>
  <path d="M200,300 L400,50 L600,300 L800,550 L1000,300"
        fill="none" stroke="#888888" stroke-width="2" />
</svg>

You first load the XML as a Document:

DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
DocumentBuilder builder = factory.newDocumentBuilder();
Document document = builder.parse("image.svg");

Then you use XPath to select the desired nodes. The expression below selects the contents of the d attributes of all the path elements inside the file:

String xpathExpression = "//path/@d";

Now we can instantiate the XPath processor and compile the expression:

XPathFactory xpf = XPathFactory.newInstance();
XPath xpath = xpf.newXPath();
XPathExpression expression = xpath.compile(xpathExpression);

Since the expected result is a node-set (two strings), we evaluate the expression on the SVG document using XPathConstants.NODESET as the second parameter:

NodeList svgPaths = (NodeList)expression.evaluate(document, XPathConstants.NODESET);

From there you can extract the first set of path data using:

svgPaths.item(0).getNodeValue();