Build-time Rendering

Many applications ship raster images derived from an SVG kept in version control: PWA icons, favicons, app store icons, Open Graph images. JairoSVG's CLI can be run during the build to produce them, so no bitmaps need to be committed and no external tools (Inkscape, ImageMagick, a headless browser) are required.

No dedicated build plugin is needed: the CLI entry point io.brunoborges.jairosvg.cli.Main is part of the regular jairosvg artifact and can be invoked in-process by your build tool.

Requirements: the build must run on Java 25+. Requires JairoSVG 1.0.15 or later (earlier versions do not create missing output directories).

Maven

Use the Exec Maven Plugin java goal with jairosvg as a plugin dependency. It does not need to be a dependency of your project.

Each <execution> renders one image. Writing into ${project.build.outputDirectory} during process-resources means the images are packaged like anything in src/main/resources.

<plugin>
    <groupId>org.codehaus.mojo</groupId>
    <artifactId>exec-maven-plugin</artifactId>
    <version>3.6.4</version>
    <dependencies>
        <dependency>
            <groupId>io.brunoborges</groupId>
            <artifactId>jairosvg</artifactId>
            <version>1.0.15</version>
        </dependency>
    </dependencies>
    <configuration>
        <mainClass>io.brunoborges.jairosvg.cli.Main</mainClass>
        <includeProjectDependencies>false</includeProjectDependencies>
        <includePluginDependencies>true</includePluginDependencies>
    </configuration>
    <executions>
        <execution>
            <id>pwa-icon-512</id>
            <phase>process-resources</phase>
            <goals>
                <goal>java</goal>
            </goals>
            <configuration>
                <arguments>
                    <argument>${project.basedir}/src/main/icons/logo.svg</argument>
                    <argument>-o</argument>
                    <argument>${project.build.outputDirectory}/META-INF/resources/icons/icon-512.png</argument>
                    <argument>--output-width</argument>
                    <argument>512</argument>
                    <argument>--output-height</argument>
                    <argument>512</argument>
                </arguments>
            </configuration>
        </execution>
    </executions>
</plugin>

Run mvn process-resources to refresh the images without a full build.

Several sizes from one SVG

Add one execution per output. Configuration shared by all executions (such as mainClass) stays at plugin level:

<execution>
    <id>pwa-icon-192</id>
    <phase>process-resources</phase>
    <goals><goal>java</goal></goals>
    <configuration>
        <arguments>
            <argument>${project.basedir}/src/main/icons/logo.svg</argument>
            <argument>-o</argument>
            <argument>${project.build.outputDirectory}/META-INF/resources/icons/icon-192.png</argument>
            <argument>--output-width</argument><argument>192</argument>
            <argument>--output-height</argument><argument>192</argument>
        </arguments>
    </configuration>
</execution>
<execution>
    <id>apple-touch-icon</id>
    <phase>process-resources</phase>
    <goals><goal>java</goal></goals>
    <configuration>
        <arguments>
            <argument>${project.basedir}/src/main/icons/logo.svg</argument>
            <argument>-o</argument>
            <argument>${project.build.outputDirectory}/META-INF/resources/icons/apple-touch-icon.png</argument>
            <argument>--output-width</argument><argument>180</argument>
            <argument>--output-height</argument><argument>180</argument>
            <!-- iOS does not support transparent touch icons -->
            <argument>-b</argument><argument>white</argument>
        </arguments>
    </configuration>
</execution>

Output format and size

The output file extension selects the format: .png, .jpg/.jpeg, .tif/.tiff, .pdf, .ps, .eps. Use -f to set it explicitly.
With only --output-width or --output-height, the other dimension follows the SVG's aspect ratio. With neither, the SVG's own size is used (optionally multiplied by -s).
-b COLOR paints a background; PNG and TIFF are transparent otherwise.
PDF output needs Apache PDFBox: add org.apache.pdfbox:pdfbox to the plugin <dependencies>.

See the CLI Reference for all options. Unknown options and invalid values fail the build.

Writing to a generated-resources directory

If you prefer the conventional target/generated-resources layout (for example so other plugins can pick up the images), render in generate-resources and register the directory with the Build Helper Maven Plugin:

<!-- in each exec-maven-plugin execution -->
<phase>generate-resources</phase>
...
<argument>-o</argument>
<argument>${project.build.directory}/generated-resources/icons/META-INF/resources/icons/icon-512.png</argument>

<!-- and -->
<plugin>
    <groupId>org.codehaus.mojo</groupId>
    <artifactId>build-helper-maven-plugin</artifactId>
    <version>3.6.1</version>
    <executions>
        <execution>
            <id>add-rendered-icons</id>
            <phase>generate-resources</phase>
            <goals><goal>add-resource</goal></goals>
            <configuration>
                <resources>
                    <resource>
                        <directory>${project.build.directory}/generated-resources/icons</directory>
                    </resource>
                </resources>
            </configuration>
        </execution>
    </executions>
</plugin>

Gradle

val jairosvg by configurations.creating

dependencies {
    jairosvg("io.brunoborges:jairosvg:1.0.15")
}

val renderIcons by tasks.registering(JavaExec::class) {
    val svg = file("src/main/icons/logo.svg")
    val out = layout.buildDirectory.file("generated-resources/icons/META-INF/resources/icons/icon-512.png")
    inputs.file(svg)
    outputs.file(out)
    classpath = jairosvg
    mainClass.set("io.brunoborges.jairosvg.cli.Main")
    args(svg.path, "-o", out.get().asFile.path, "--output-width", "512", "--output-height", "512")
}

sourceSets.main {
    resources.srcDir(layout.buildDirectory.dir("generated-resources/icons"))
}

tasks.processResources {
    dependsOn(renderIcons)
}

Gradle's input/output tracking skips the task when neither the SVG nor the arguments changed.

Acknowledgements

This recipe was inspired by viritin/svg-render-maven-plugin, a dedicated plugin built on JairoSVG that offers extra conveniences such as {size} placeholders and incremental rendering.