Java Batik resize SVG to panel size keeping aspect ratio

Question

I'm trying to display an SVG Image on my swing application, since i don't have an SVG file but a path i'm converting the path to a valid svg document with:

private static Document buildSVGDocument(Color svgColor, /*double svgWidth, double svgHeight,*/ String svgPath) {
    DOMImplementation svgDocumentImplementation = SVGDOMImplementation.getDOMImplementation();
    Document svgDocument = svgDocumentImplementation.createDocument(SVGDOMImplementation.SVG_NAMESPACE_URI, "svg", null);

    Element svgDocumentElement = svgDocument.getDocumentElement();
    //svgDocumentElement.setAttribute("height", String.valueOf(svgHeight));
    //svgDocumentElement.setAttribute("width", String.valueOf(svgWidth));

    Element svgDocumentPath = svgDocument.createElementNS(SVGDOMImplementation.SVG_NAMESPACE_URI, "path");
    svgDocumentPath.setAttribute("style", String.format("fill:rgb(%s, %s, %s);", svgColor.getRed(), svgColor.getGreen(), svgColor.getBlue()));
    svgDocumentPath.setAttribute("d", svgPath);
    svgDocumentElement.appendChild(svgDocumentPath);

    return svgDocument;
}

Then I display the SVG Document on a Batik Canvas:

JSVGCanvas panel = new JSVGCanvas();
panel.setDocumentState(JSVGCanvas.ALWAYS_DYNAMIC);
panel.setDisableInteractions(true);
panel.setDocument(buildSVGDocument(/*etc*/));
container.add(panel, BorderLayout.WEST);

Now my question is: how do I resize the svg to the panel size keeping the aspect-ratio?

Answer 1

I figured out how to do it!, Browsing the source I found the method used to calculate the image scale, it's:

calculateViewingTransform

Then I've implemented a simple class to scale the image to the container

public class SVGCanvas extends JSVGCanvas {

    private static final long serialVersionUID = 1L;

    /**
     * The type of scale
     */
    private short svgScale;

    /**
     * Image padding
     */
    private int svgPadding;

    public SVGCanvas() {
        this.svgScale = SVGPreserveAspectRatio.SVG_PRESERVEASPECTRATIO_XMIDYMAX;
        this.svgPadding = 5;
    }

    @Override
    protected AffineTransform calculateViewingTransform(String svgElementIdentifier, SVGSVGElement svgElement) {
        SVGRect svgElementBounds = svgElement.getBBox();
        float[] svgElementBoundsVector = new float[] {
            svgElementBounds.getX(),
            svgElementBounds.getY(),
            svgElementBounds.getWidth(),
            svgElementBounds.getHeight()
        };

        float svgEemenetScaleToHeight = getHeight() - svgPadding;
        float svgElementScaleToWidth = getWidth() - svgPadding;

        return ViewBox.getPreserveAspectRatioTransform(
            svgElementBoundsVector, svgScale, true,
            svgElementScaleToWidth,
            svgEemenetScaleToHeight
        );
    }

    public void setSvgScale(short svgScale) {
        this.svgScale = svgScale;
    }

    public void setSvgPadding(int svgPadding) {
        this.svgPadding = svgPadding;
    }

}