Custom Image Transcoder

Write a custom image transcoder that can read an SVG file and transform that resource into a PNG or SVG file. When exporting as PDF, it is okay to use an SVG file directly. Consider:

import java.awt.Color;
import java.io.*;
import net.sf.jasperreports.engine.JRException;
import net.sf.jasperreports.engine.util.JRLoader;
import org.apache.batik.transcoder.*;
import static org.apache.batik.transcoder.image.ImageTranscoder.*;
import org.apache.batik.transcoder.image.PNGTranscoder;

public class ImageTranscoder {
    public static InputStream asSVG(final String file) throws JRException {
        return new ByteArrayInputStream(load(file));
    }

    public static InputStream asPNG(final String file)
            throws TranscoderException, JRException {
        return asPNG(load(file));
    }

    public static InputStream asPNG(final byte[] svg)
            throws TranscoderException {
        final ByteArrayOutputStream outBytes = new ByteArrayOutputStream();
        final ByteArrayInputStream inBytes = new ByteArrayInputStream(svg);

        final TranscoderInput input = new TranscoderInput(inBytes);
        final TranscoderOutput output = new TranscoderOutput(outBytes);
        final PNGTranscoder transcoder = new PNGTranscoder();

        transcoder.addTranscodingHint(KEY_BACKGROUND_COLOR, Color.white);
        transcoder.addTranscodingHint(KEY_FORCE_TRANSPARENT_WHITE, true);
        transcoder.transcode(input, output);

        final byte[] bytes = outBytes.toByteArray();
        return new ByteArrayInputStream(bytes);
    }

    private static byte[] load(final String file) throws JRException {
        return JRLoader.loadBytesFromResource(file);
    }
}

Import Transcoder

In the JRXML file, import the fully qualified class:

<import value="com.company.jasper.ImageTranscoder"/>

Apply Image Transcoder

Drag and drop an Image from the palette onto the report, as per usual. Set its Expression to:

ImageTranscoder.asSVG($P{IMAGES_PATH} + $P{IMAGE_FILENAME} + ".svg")

If you absolutely need a PNG version, then transcode it on-the-fly:

ImageTranscoder.asPNG($P{IMAGES_PATH} + $P{IMAGE_FILENAME} + ".svg")

HTML vs PDF

With HTML, typically PNG images are still preferred. There are a number of approaches you can take to differentiate HTML (PNG) from PDF (SVG). A simple way is to assign two different key values to two different Image elements. For example:

<image scaleImage="RetainShape" onErrorType="Blank">
    <reportElement key="IMAGE_PNG"/>
    <imageExpression><![CDATA[ImageTranscoder.asPNG(...)]]></imageExpression>
</image>
<image scaleImage="RetainShape" onErrorType="Blank">
    <reportElement key="IMAGE_SVG"/>
    <imageExpression><![CDATA[ImageTranscoder.asSVG(...)]]></imageExpression>
</image>

Then you can exclude one or the other based on the export type:

<property name="net.sf.jasperreports.export.html.exclude.key.IMAGE_SVG"/>
<property name="net.sf.jasperreports.export.pdf.exclude.key.IMAGE_PNG"/>

Summary

While it is simpler to include a PNG image, converting that PNG image from SVG is an additional step that can be avoided. Since the JasperReports Library uses the Batik engine for rendering images, leverage it to convert an SVG file to PNG when the report is generated.

This way, the SVG serves as a single source for all formats, regardless of whether a PNG or SVG file is used in the report.

Be sure to set the IMAGES_PATH and IMAGE_FILENAME parameters as appropriate.

HTML and Base64

Force the image to embed using:

<property name="net.sf.jasperreports.export.html.embed.image" value="true"/>

The PNG image becomes a Base64-encoded String:

<img src="data:image/png;base64,..."/>

This will make the report load a bit faster (no extra HTTP request for the image) and simplify the architecture as it eliminates an external dependency. That is, a web server is no longer required to serve the image, since it is wholly embedded.