Introduce SVG rasterizer logic

Feature Proposal: Rasterization of SVGs at Runtime for Eclipse Icons
Fixes #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.

---
- **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 +1,84 @@
+/*******************************************************************************
+ * Copyright (c) 2023 Vector Informatik GmbH and others.
+ *
+ * This program and the accompanying materials are made available under the terms of the Eclipse
+ * Public License 2.0 which accompanies this distribution, and is available at
+ * https://www.eclipse.org/legal/epl-2.0/
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ *
+ * Contributors: Vector Informatik GmbH - initial API and implementation
+ *******************************************************************************/
+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 {
+
+	private SVGLoader svgLoader;
+
+	/**
+	 * 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 {
+		if(svgLoader == null) {
+			svgLoader = new SVGLoader();
+		}
+		SVGDocument svgDocument = null;
+		if (SVGUtil.isSVGFile(bytes)) {
+			try (InputStream stream = new ByteArrayInputStream(bytes)) {
+				svgDocument = svgLoader.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/cocoa/org/eclipse/swt/graphics/ImageLoader.java

@@ -14,9 +14,12 @@
 package org.eclipse.swt.graphics;
 
 
+import java.awt.image.BufferedImage;
 import java.io.*;
 import java.util.*;
 
+import javax.imageio.ImageIO;
+
 import org.eclipse.swt.*;
 import org.eclipse.swt.internal.image.*;
 
@@ -149,10 +152,72 @@ void reset() {
  * </ul>
  */
 public ImageData[] load(InputStream stream) {
+	return loadDefault(stream);
+}
+
+private ImageData[] loadDefault(InputStream stream) {
 	if (stream == null) SWT.error(SWT.ERROR_NULL_ARGUMENT);
 	reset();
 	data = FileFormat.load(stream, this);
-	return data;
+    return data;
+}
+
+/**
+ * Loads an array of <code>ImageData</code> objects from the
+ * specified input stream. If the stream is a SVG File and zoom is not 0,
+ * this method will try to rasterize the SVG.
+ * Throws an error if either an error occurs while loading the images, or if the images are not
+ * of a supported type. Returns the loaded image data array.
+ *
+ * @param stream the input stream to load the images from
+ * @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.
+ * @return an array of <code>ImageData</code> objects loaded from the specified input stream
+ *
+ * @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>
+ *
+ * @since 3.129
+ */
+public ImageData[] load(InputStream stream, int zoom) {
+	if (stream == null) SWT.error(SWT.ERROR_NULL_ARGUMENT);
+    reset();
+    byte[] bytes = null;
+	try {
+		bytes = stream.readAllBytes();
+	} catch (IOException e) {
+		SWT.error(SWT.ERROR_IO, e);
+	}
+	ISVGRasterizer rasterizer = SVGRasterizerRegistry.getRasterizer();
+	if (rasterizer != null && zoom != 0) {
+	    try {
+	    	float scalingFactor = zoom / 100.0f;
+	    	BufferedImage image = rasterizer.rasterizeSVG(bytes, scalingFactor);
+	    	if(image != null) {
+	    		try (ByteArrayOutputStream baos = new ByteArrayOutputStream()) {
+	        	    ImageIO.write(image, "png", baos);
+	        	    try (InputStream in = new ByteArrayInputStream(baos.toByteArray())) {
+	        	    	data = FileFormat.load(in, this);
+	        		    return data;
+	        	    }
+	        	}
+	    	}
+	    } catch (IOException e) {
+	        // try standard method
+	    }
+	}
+	try (InputStream fallbackStream = new ByteArrayInputStream(bytes)) {
+		return loadDefault(fallbackStream);
+	} catch (IOException e) {
+		SWT.error(SWT.ERROR_IO, e);
+	}
+	return null;
 }
 
 /**
@@ -175,18 +240,43 @@ public ImageData[] load(InputStream stream) {
  */
 public ImageData[] load(String filename) {
 	if (filename == null) SWT.error(SWT.ERROR_NULL_ARGUMENT);
-	InputStream stream = null;
-	try {
-		stream = new FileInputStream(filename);
-		return load(stream);
+	try (InputStream stream = new FileInputStream(filename)) {
+		return loadDefault(stream);
+	} catch (IOException e) {
+		SWT.error(SWT.ERROR_IO, e);
+	}
+	return null;
+}
+
+/**
+ * Loads an array of <code>ImageData</code> objects from the
+ * file with the specified name. If the filename is a SVG File and zoom is not 0,
+ * this method will try to rasterize the SVG. Throws an error if either
+ * an error occurs while loading the images, or if the images are
+ * not of a supported type. Returns the loaded image data array.
+ *
+ * @param filename the name of the file to load the images from
+ * @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.
+ * @return an array of <code>ImageData</code> objects loaded from the specified file
+ *
+ * @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[] load(String filename, int zoom) {
+	if (filename == null) SWT.error(SWT.ERROR_NULL_ARGUMENT);
+	try (InputStream stream = new FileInputStream(filename)) {
+		return load(stream, zoom);
 	} catch (IOException e) {
 		SWT.error(SWT.ERROR_IO, e);
-	} finally {
-		try {
-			if (stream != null) stream.close();
-		} catch (IOException e) {
-			// Ignore error
-		}
 	}
 	return null;
 }

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

@@ -0,0 +1,38 @@
+/*******************************************************************************
+ * Copyright (c) 2024 Vector Informatik GmbH and others.
+ *
+ * This program and the accompanying materials are made available under the terms of the Eclipse
+ * Public License 2.0 which accompanies this distribution, and is available at
+ * https://www.eclipse.org/legal/epl-2.0/
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ *
+ * Contributors: Vector Informatik GmbH - initial API and implementation
+ *******************************************************************************/
+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;
+
+}