Introduce SVG rasterizer logic

Feature Proposal: Rasterization of SVGs at Runtime for Eclipse Icons
Fixes eclipse-platform#1438

Eclipse currently loads icons exclusively as raster graphics (e.g., `.png`), without support for vector formats like `.svg`. A major drawback of raster graphics is their inability to scale without degrading image quality. Additionally, generating icons of different sizes requires manually rasterizing SVGs outside Eclipse, leading to unnecessary effort and many icon files.

This PR introduces support for vector graphics in Eclipse, enabling SVGs to be used for icons. Existing PNG icons will continue to be loaded alongside SVGs, allowing the use of the new functionality without the need to replace all PNG files at once.

---

### **Key Features**

- **Example Images**:
  Screenshots showcasing the new functionality can be found below. These screenshots were taken with 125% monitor-zoom and scaling enabled with the flag `-Dswt.autoScale=quarter`.

| PNG      | SVG      |
|---------------|---------------|
| ![PNG](https://github.com/user-attachments/assets/6ecd1eb2-8716-465f-9206-e64ae9e17e7a)  | ![SVG](https://github.com/user-attachments/assets/44d69279-18a0-46de-9972-a529eff5da66)  |
| ![PNG2](https://github.com/user-attachments/assets/0ba6c210-1b0e-4f75-8fc5-f8b40d5c97b4)  | ![SVG2](https://github.com/user-attachments/assets/d8892fd4-c374-4152-9458-b7d50ed54157)  |
| ![PNG3](https://github.com/user-attachments/assets/d3c5668f-a4a3-4b9f-8ad4-73072c258abc)  | ![SVG3](https://github.com/user-attachments/assets/8f20bbf6-30d8-41cb-9775-ddbdad7398a4)  |
| ![PNG4](https://github.com/user-attachments/assets/dbbd7b6c-4e58-415e-8a13-ba3557f2dca6)  | ![SVG4](https://github.com/user-attachments/assets/95270a6b-b550-4652-afe5-43d35444b1df)  |

- **How It Works**:
  - To use SVG icons, simply place the SVG file in the bundle and reference it in the `plugin.xml` and other necessary locations, as is done for PNGs. No additional configuration is required.
  - At runtime, Eclipse uses the library JSVG to rasterize the SVG into a raster image of the desired size, eliminating the need for scaling. My analysis shows that JSVG is the most suitable Java library for this purpose.
  - You need to write the flag `-Dswt.autoScale=quarter` into your `eclipse.ini` file or into the run arguments of a new configuration.

bundles/org.eclipse.swt.svg/.classpath

@@ -0,0 +1,8 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<classpath>
+	<classpathentry kind="con" path="org.eclipse.jdt.launching.JRE_CONTAINER/org.eclipse.jdt.internal.debug.ui.launcher.StandardVMType/JavaSE-17"/>
+	<classpathentry kind="con" path="org.eclipse.pde.core.requiredPlugins"/>
+	<classpathentry kind="src" path="src"/>
+	<classpathentry kind="lib" path="libs/jsvg-1.6.1.jar"/>
+	<classpathentry kind="output" path="bin"/>
+</classpath>

bundles/org.eclipse.swt.svg/.project

@@ -0,0 +1,28 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<projectDescription>
+	<name>org.eclipse.swt.svg</name>
+	<comment></comment>
+	<projects>
+	</projects>
+	<buildSpec>
+		<buildCommand>
+			<name>org.eclipse.jdt.core.javabuilder</name>
+			<arguments>
+			</arguments>
+		</buildCommand>
+		<buildCommand>
+			<name>org.eclipse.pde.ManifestBuilder</name>
+			<arguments>
+			</arguments>
+		</buildCommand>
+		<buildCommand>
+			<name>org.eclipse.pde.SchemaBuilder</name>
+			<arguments>
+			</arguments>
+		</buildCommand>
+	</buildSpec>
+	<natures>
+		<nature>org.eclipse.pde.PluginNature</nature>
+		<nature>org.eclipse.jdt.core.javanature</nature>
+	</natures>
+</projectDescription>

bundles/org.eclipse.swt.svg/.settings/org.eclipse.core.resources.prefs

@@ -0,0 +1,2 @@
+eclipse.preferences.version=1
+encoding/<project>=UTF-8

bundles/org.eclipse.swt.svg/.settings/org.eclipse.jdt.core.prefs

@@ -0,0 +1,9 @@
+eclipse.preferences.version=1
+org.eclipse.jdt.core.compiler.codegen.targetPlatform=17
+org.eclipse.jdt.core.compiler.compliance=17
+org.eclipse.jdt.core.compiler.problem.assertIdentifier=error
+org.eclipse.jdt.core.compiler.problem.enablePreviewFeatures=disabled
+org.eclipse.jdt.core.compiler.problem.enumIdentifier=error
+org.eclipse.jdt.core.compiler.problem.reportPreviewFeatures=warning
+org.eclipse.jdt.core.compiler.release=enabled
+org.eclipse.jdt.core.compiler.source=17

bundles/org.eclipse.swt.svg/META-INF/MANIFEST.MF

@@ -0,0 +1,10 @@
+Manifest-Version: 1.0
+Bundle-ManifestVersion: 2
+Bundle-Name: SvgPlugin
+Bundle-SymbolicName: org.eclipse.swt.svg
+Bundle-Version: 1.0.0.qualifier
+Automatic-Module-Name: org.eclipse.swt.svgPlugin
+Bundle-RequiredExecutionEnvironment: JavaSE-17
+Export-Package: org.eclipse.swt.svg
+Import-Package: org.eclipse.swt.graphics
+Bundle-ClassPath: ., libs/jsvg-1.6.1.jar

bundles/org.eclipse.swt.svg/build.properties

@@ -0,0 +1,5 @@
+source.. = src/
+output.. = bin/
+bin.includes = META-INF/,\
+               .,\
+               libs/jsvg-1.6.1.jar

bundles/org.eclipse.swt.svg/src/org/eclipse/swt/svg/SVGRasterizer.java

@@ -0,0 +1,69 @@
+package org.eclipse.swt.svg;
+
+import static java.awt.RenderingHints.*;
+
+import java.awt.*;
+import java.awt.image.*;
+import java.io.*;
+import java.util.*;
+import org.eclipse.swt.graphics.ISVGRasterizer;
+import org.eclipse.swt.graphics.SVGRasterizerRegistry;
+import org.eclipse.swt.graphics.SVGUtil;
+
+import com.github.weisj.jsvg.*;
+import com.github.weisj.jsvg.geometry.size.*;
+import com.github.weisj.jsvg.parser.*;
+
+/**
+ * A rasterizer implementation for converting SVG data into rasterized images.
+ * This class implements the {@code ISVGRasterizer} interface.
+ * 
+ * @since 1.0.0
+ */
+public class SVGRasterizer implements ISVGRasterizer {
+
+	/**
+	 * Initializes the SVG rasterizer by registering an instance of this rasterizer
+	 * with the {@link SVGRasterizerRegistry}.
+	 */
+	public static void intializeSVGRasterizer() {
+		SVGRasterizerRegistry.register(new SVGRasterizer());
+	}
+
+	private final static Map<Key, Object> RENDERING_HINTS = Map.of(KEY_ANTIALIASING, VALUE_ANTIALIAS_ON, //
+			KEY_ALPHA_INTERPOLATION, VALUE_ALPHA_INTERPOLATION_QUALITY, //
+			KEY_COLOR_RENDERING, VALUE_COLOR_RENDER_QUALITY, //
+			KEY_DITHERING, VALUE_DITHER_DISABLE, //
+			KEY_FRACTIONALMETRICS, VALUE_FRACTIONALMETRICS_ON, //
+			KEY_INTERPOLATION, VALUE_INTERPOLATION_BICUBIC, //
+			KEY_RENDERING, VALUE_RENDER_QUALITY, //
+			KEY_STROKE_CONTROL, VALUE_STROKE_PURE, //
+			KEY_TEXT_ANTIALIASING, VALUE_TEXT_ANTIALIAS_ON //
+	);
+
+	@Override
+	public BufferedImage rasterizeSVG(byte[] bytes, float scalingFactor) throws IOException {
+		SVGLoader loader = new SVGLoader();
+		SVGDocument svgDocument = null;
+		if (SVGUtil.isSVGFile(bytes)) {
+			try (InputStream stream = new ByteArrayInputStream(bytes)) {
+				svgDocument = loader.load(stream, null, LoaderContext.createDefault());
+			}
+			if (svgDocument != null) {
+				FloatSize size = svgDocument.size();
+				double originalWidth = size.getWidth();
+				double originalHeight = size.getHeight();
+				int scaledWidth = (int) Math.round(originalWidth * scalingFactor);
+				int scaledHeight = (int) Math.round(originalHeight * scalingFactor);
+				BufferedImage image = new BufferedImage(scaledWidth, scaledHeight, BufferedImage.TYPE_INT_ARGB);
+				Graphics2D g = image.createGraphics();
+				g.setRenderingHints(RENDERING_HINTS);
+				g.scale(scalingFactor, scalingFactor);
+				svgDocument.render(null, g);
+				g.dispose();
+				return image;
+			}
+		}
+		return null;
+	}
+}

bundles/org.eclipse.swt/Eclipse SWT/common/org/eclipse/swt/graphics/ISVGRasterizer.java

@@ -0,0 +1,27 @@
+package org.eclipse.swt.graphics;
+
+import java.awt.image.*;
+import java.io.*;
+
+/**
+ * Defines the interface for an SVG rasterizer, responsible for converting SVG
+ * data into rasterized images.
+ *
+ * @since 3.129
+ */
+public interface ISVGRasterizer {
+
+	/**
+	 * Rasterizes an SVG image from the provided byte array, using the specified
+	 * zoom factor.
+	 *
+	 * @param bytes         the SVG image as a byte array.
+	 * @param scalingFactor the scaling ratio e.g. 2.0 for doubled size.
+	 * @return a {@link BufferedImage} containing the rasterized image, or
+	 *         {@code null} if the input is not a valid SVG file or cannot be
+	 *         processed.
+	 * @throws IOException if an error occurs while reading the SVG data.
+	 */
+	public BufferedImage rasterizeSVG(byte[] bytes, float scalingFactor) throws IOException;
+
+}

bundles/org.eclipse.swt/Eclipse SWT/common/org/eclipse/swt/graphics/ImageData.java

@@ -331,7 +331,39 @@ scanlinePad, checkData(data), 0, null,
  * @see ImageLoader#load(InputStream)
  */
 public ImageData(InputStream stream) {
-	ImageData[] data = ImageDataLoader.load(stream);
+	this(stream, 0);
+}
+
+/**
+ * Constructs an <code>ImageData</code> loaded from the specified
+ * input stream. Throws an error if an error occurs while loading
+ * the image, or if the image has an unsupported type.  Application
+ * code is still responsible for closing the input stream.
+ * <p>
+ * This constructor is provided for convenience when loading a single
+ * image only. If the stream contains multiple images, only the first
+ * one will be loaded. To load multiple images, use
+ * <code>ImageLoader.load()</code>.
+ * </p>
+ *
+ * @param stream the input stream to load the image from (must not be null)
+ * @param zoom the zoom factor to apply when rasterizing a SVG.
+ * A value of 0 means that the standard method for loading should be used.
+ *
+ * @exception IllegalArgumentException <ul>
+ *    <li>ERROR_NULL_ARGUMENT - if the stream is null</li>
+ * </ul>
+ * @exception SWTException <ul>
+ *    <li>ERROR_IO - if an IO error occurs while reading from the stream</li>
+ *    <li>ERROR_INVALID_IMAGE - if the image stream contains invalid data</li>
+ *    <li>ERROR_UNSUPPORTED_FORMAT - if the image stream contains an unrecognized format</li>
+ * </ul>
+ *
+ * @see ImageLoader#load(InputStream)
+ * @since 3.129
+ */
+public ImageData(InputStream stream, int zoom) {
+	ImageData[] data = ImageDataLoader.load(stream, zoom);
 	if (data.length < 1) SWT.error(SWT.ERROR_INVALID_IMAGE);
 	ImageData i = data[0];
 	setAllFields(
@@ -377,7 +409,36 @@ public ImageData(InputStream stream) {
  * </ul>
  */
 public ImageData(String filename) {
-	ImageData[] data = ImageDataLoader.load(filename);
+	this(filename, 0);
+}
+
+/**
+ * Constructs an <code>ImageData</code> loaded from a file with the
+ * specified name. Throws an error if an error occurs loading the
+ * image, or if the image has an unsupported type.
+ * <p>
+ * This constructor is provided for convenience when loading a single
+ * image only. If the file contains multiple images, only the first
+ * one will be loaded. To load multiple images, use
+ * <code>ImageLoader.load()</code>.
+ * </p>
+ *
+ * @param filename the name of the file to load the image from (must not be null)
+ * @param zoom the zoom factor to apply when rasterizing a SVG.
+ * A value of 0 means that the standard method for loading should be used.
+ * @exception IllegalArgumentException <ul>
+ *    <li>ERROR_NULL_ARGUMENT - if the file name is null</li>
+ * </ul>
+ * @exception SWTException <ul>
+ *    <li>ERROR_IO - if an IO error occurs while reading from the file</li>
+ *    <li>ERROR_INVALID_IMAGE - if the image file contains invalid data</li>
+ *    <li>ERROR_UNSUPPORTED_FORMAT - if the image file contains an unrecognized format</li>
+ * </ul>
+ *
+ * @since 3.129
+ */
+public ImageData(String filename, int zoom) {
+	ImageData[] data = ImageDataLoader.load(filename, zoom);
 	if (data.length < 1) SWT.error(SWT.ERROR_INVALID_IMAGE);
 	ImageData i = data[0];
 	setAllFields(

bundles/org.eclipse.swt/Eclipse SWT/common/org/eclipse/swt/graphics/ImageDataLoader.java

@@ -25,8 +25,16 @@ public static ImageData[] load(InputStream stream) {
 		return new ImageLoader().load(stream);
 	}
 
-	public static ImageData[] load(String filename) {
+	public static ImageData[] load(InputStream stream, int zoom) {
+		return new ImageLoader().load(stream, zoom);
+	}
+
+		public static ImageData[] load(String filename) {
 		return new ImageLoader().load(filename);
 	}
 
+	public static ImageData[] load(String filename, int zoom) {
+		return new ImageLoader().load(filename, zoom);
+	}
+
 }

bundles/org.eclipse.swt/Eclipse SWT/common/org/eclipse/swt/graphics/SVGRasterizerRegistry.java

@@ -0,0 +1,38 @@
+package org.eclipse.swt.graphics;
+
+/**
+ * A registry for managing the instance of an {@link ISVGRasterizer} implementation.
+ * This allows for the registration and retrieval of a single rasterizer instance.
+ *
+ * @since 3.129
+ */
+public class SVGRasterizerRegistry {
+
+	/**
+     * The instance of the registered {@link ISVGRasterizer}.
+     */
+	private static ISVGRasterizer rasterizer;
+
+	 /**
+     * Registers the provided implementation of {@link ISVGRasterizer}.
+     * If a rasterizer has already been registered, subsequent calls to this method
+     * will have no effect.
+     *
+     * @param implementation the {@link ISVGRasterizer} implementation to register.
+     */
+	public static void register(ISVGRasterizer implementation) {
+		if (rasterizer == null) {
+			rasterizer = implementation;
+		}
+	}
+
+	/**
+     * Retrieves the currently registered {@link ISVGRasterizer} implementation.
+     *
+     * @return the registered {@link ISVGRasterizer}, or {@code null} if no implementation
+     *         has been registered.
+     */
+	public static ISVGRasterizer getRasterizer() {
+		return rasterizer;
+	}
+}

bundles/org.eclipse.swt/Eclipse SWT/common/org/eclipse/swt/graphics/SVGUtil.java

@@ -0,0 +1,43 @@
+package org.eclipse.swt.graphics;
+
+import java.io.*;
+import java.nio.charset.*;
+
+/**
+ * Utility class for handling SVG-related operations.
+ *
+ * @since 3.129
+ */
+public class SVGUtil {
+
+	/**
+	 * Determines whether the given {@link InputStream} contains a SVG file.
+	 *
+	 * @param data byte array to check.
+	 * @return {@code true} if the input stream contains SVG content; {@code false}
+	 *         otherwise.
+	 * @throws IOException              if an error occurs while reading the stream.
+	 * @throws IllegalArgumentException if the input stream is {@code null}.
+	 */
+	public static boolean isSVGFile(byte[] data) throws IOException {
+		String content = new String(data, 0, Math.min(data.length, 512), StandardCharsets.UTF_8);
+		return content.contains("<svg");
+	}
+
+	/**
+	 * Determines whether the given {@link InputStream} contains a SVG file.
+	 *
+	 * @param inputStream the input stream to check.
+	 * @return {@code true} if the input stream contains SVG content; {@code false}
+	 *         otherwise.
+	 * @throws IOException              if an error occurs while reading the stream.
+	 * @throws IllegalArgumentException if the input stream is {@code null}.
+	 */
+	public static boolean isSVGFile(InputStream inputStream) throws IOException {
+		if (inputStream == null) {
+			throw new IllegalArgumentException("InputStream cannot be null");
+		}
+		byte[] data = inputStream.readNBytes(512);
+		return isSVGFile(data);
+	}
+}

bundles/org.eclipse.swt/Eclipse SWT/win32/org/eclipse/swt/graphics/Image.java

@@ -468,7 +468,7 @@ public Image(Device device, ImageData source, ImageData mask) {
 public Image (Device device, InputStream stream) {
 	super(device);
 	initialNativeZoom = DPIUtil.getNativeDeviceZoom();
-	ImageData data = DPIUtil.autoScaleUp(device, new ElementAtZoom<>(new ImageData (stream), 100));
+	ImageData data = DPIUtil.autoScaleUp(device, new ElementAtZoom<>(new ImageData (stream, getZoom()), 100));
 	init(data, getZoom());
 	init();
 	this.device.registerResourceWithZoomSupport(this);
@@ -510,7 +510,7 @@ public Image (Device device, String filename) {
 	super(device);
 	if (filename == null) SWT.error(SWT.ERROR_NULL_ARGUMENT);
 	initialNativeZoom = DPIUtil.getNativeDeviceZoom();
-	ImageData data = DPIUtil.autoScaleUp(device, new ElementAtZoom<>(new ImageData (filename), 100));
+	ImageData data = DPIUtil.autoScaleUp(device, new ElementAtZoom<>(new ImageData (filename, getZoom()), 100));
 	init(data, getZoom());
 	init();
 	this.device.registerResourceWithZoomSupport(this);
@@ -553,10 +553,10 @@ public Image(Device device, ImageFileNameProvider imageFileNameProvider) {
 	if (fileName.zoom() == getZoom()) {
 		ImageHandle imageMetadata = initNative (fileName.element(), getZoom());
 		if (imageMetadata == null) {
-			init(new ImageData (fileName.element()), getZoom());
+			init(new ImageData (fileName.element(), getZoom()), getZoom());
 		}
 	} else {
-		ImageData resizedData = DPIUtil.autoScaleImageData (device, new ImageData (fileName.element()), fileName.zoom());
+		ImageData resizedData = DPIUtil.autoScaleImageData (device, new ImageData (fileName.element(), getZoom()), fileName.zoom());
 		init(resizedData, getZoom());
 	}
 	init();
@@ -753,7 +753,7 @@ private ImageHandle getImageMetadata(int zoom) {
 
 	if (imageFileNameProvider != null) {
 		ElementAtZoom<String> imageCandidate = DPIUtil.validateAndGetImagePathAtZoom (imageFileNameProvider, zoom);
-		ImageData imageData = new ImageData (imageCandidate.element());
+		ImageData imageData = new ImageData (imageCandidate.element(), zoom);
 		if (imageCandidate.zoom() == zoom) {
 			/* Release current native resources */
 			ImageHandle imageMetadata = initNative(imageCandidate.element(), zoom);
@@ -1389,7 +1389,7 @@ public ImageData getImageData (int zoom) {
 		return DPIUtil.scaleImageData (device, data.element(), zoom, data.zoom());
 	} else if (imageFileNameProvider != null) {
 		ElementAtZoom<String> fileName = DPIUtil.validateAndGetImagePathAtZoom (imageFileNameProvider, zoom);
-		return DPIUtil.scaleImageData (device, new ImageData (fileName.element()), zoom, fileName.zoom());
+		return DPIUtil.scaleImageData (device, new ImageData (fileName.element(), zoom), zoom, fileName.zoom());
 	}
 
 	// if a GC is initialized with an Image (memGC != null), the image data must not be resized, because it would