issue 38

jhotdraw-core/src/main/java/org/jhotdraw/draw/io/ImageFormatProvider.java

@@ -0,0 +1,72 @@
+/*
+ * @(#)ImageFormatProvider.java
+ *
+ * Copyright (c) 2025 The authors and contributors of JHotDraw.
+ * You may not use, copy or modify this file, except in compliance with the
+ * accompanying license terms.
+ */
+package org.jhotdraw.draw.io;
+
+import org.jhotdraw.draw.figure.ImageHolderFigure;
+
+/**
+ * A provider interface for image format support.
+ * 
+ * <p>Implementations of this interface define how to create input and output
+ * formats for specific image types (PNG, JPEG, GIF, etc.).</p>
+ * 
+ * <p>To add support for a new image format:</p>
+ * <ol>
+ *   <li>Implement this interface</li>
+ *   <li>Register with {@link ImageFormatRegistry#registerProvider(ImageFormatProvider)}</li>
+ *   <li>Or add to META-INF/services/org.jhotdraw.draw.io.ImageFormatProvider for SPI</li>
+ * </ol>
+ * 
+ * @author JHotDraw
+ * @version $Id$
+ */
+public interface ImageFormatProvider {
+
+    /**
+     * Returns the format name (e.g., "PNG", "JPEG").
+     * 
+     * @return the format name
+     */
+    String getFormatName();
+
+    /**
+     * Returns a human-readable description of the format.
+     * 
+     * @return the format description
+     */
+    String getDescription();
+
+    /**
+     * Returns the file extensions supported by this format.
+     * 
+     * @return array of file extensions (without dots)
+     */
+    String[] getFileExtensions();
+
+    /**
+     * Returns the MIME types supported by this format.
+     * 
+     * @return array of MIME types
+     */
+    String[] getMimeTypes();
+
+    /**
+     * Creates an input format for reading images of this type.
+     * 
+     * @param prototype the prototype figure for holding the image
+     * @return an InputFormat instance
+     */
+    InputFormat createInputFormat(ImageHolderFigure prototype);
+
+    /**
+     * Creates an output format for writing images of this type.
+     * 
+     * @return an OutputFormat instance, or null if output is not supported
+     */
+    OutputFormat createOutputFormat();
+}

jhotdraw-core/src/main/java/org/jhotdraw/draw/io/ImageFormatRegistry.java

@@ -0,0 +1,129 @@
+/*
+ * @(#)ImageFormatRegistry.java
+ *
+ * Copyright (c) 2025 The authors and contributors of JHotDraw.
+ * You may not use, copy or modify this file, except in compliance with the
+ * accompanying license terms.
+ */
+package org.jhotdraw.draw.io;
+
+import org.jhotdraw.draw.figure.ImageHolderFigure;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+import java.util.ServiceLoader;
+
+/**
+ * A registry for image format handlers that provides a modular way to 
+ * add support for various image formats (PNG, JPEG, GIF, etc.).
+ * 
+ * <p>This class uses the Service Provider Interface (SPI) pattern to allow
+ * dynamic registration of image format handlers.</p>
+ * 
+ * <p><b>Usage:</b></p>
+ * <pre>
+ * // Get all registered input formats for a prototype figure
+ * List&lt;InputFormat&gt; formats = ImageFormatRegistry.getInputFormats(myImageFigure);
+ * drawing.getInputFormats().addAll(formats);
+ * </pre>
+ * 
+ * @author JHotDraw
+ * @version $Id$
+ */
+public final class ImageFormatRegistry {
+
+    private static final List<ImageFormatProvider> providers = new ArrayList<>();
+
+    static {
+        // Register default providers
+        registerProvider(new PngFormatProvider());
+        registerProvider(new JpegFormatProvider());
+
+        // Load additional providers via SPI
+        ServiceLoader<ImageFormatProvider> loader = ServiceLoader.load(ImageFormatProvider.class);
+        for (ImageFormatProvider provider : loader) {
+            registerProvider(provider);
+        }
+    }
+
+    private ImageFormatRegistry() {
+        // Prevent instantiation
+    }
+
+    /**
+     * Registers a new image format provider.
+     * 
+     * @param provider the provider to register
+     */
+    public static void registerProvider(ImageFormatProvider provider) {
+        if (provider != null && !providers.contains(provider)) {
+            providers.add(provider);
+        }
+    }
+
+    /**
+     * Unregisters an image format provider.
+     * 
+     * @param provider the provider to unregister
+     */
+    public static void unregisterProvider(ImageFormatProvider provider) {
+        providers.remove(provider);
+    }
+
+    /**
+     * Returns all registered providers.
+     * 
+     * @return an unmodifiable list of providers
+     */
+    public static List<ImageFormatProvider> getProviders() {
+        return Collections.unmodifiableList(providers);
+    }
+
+    /**
+     * Creates input formats for all registered image format providers.
+     * 
+     * @param prototype the prototype figure to use for creating image holders
+     * @return a list of input formats
+     */
+    public static List<InputFormat> createInputFormats(ImageHolderFigure prototype) {
+        List<InputFormat> formats = new ArrayList<>();
+        for (ImageFormatProvider provider : providers) {
+            formats.add(provider.createInputFormat(prototype));
+        }
+        return formats;
+    }
+
+    /**
+     * Creates output formats for all registered image format providers.
+     * 
+     * @return a list of output formats
+     */
+    public static List<OutputFormat> createOutputFormats() {
+        List<OutputFormat> formats = new ArrayList<>();
+        for (ImageFormatProvider provider : providers) {
+            OutputFormat format = provider.createOutputFormat();
+            if (format != null) {
+                formats.add(format);
+            }
+        }
+        return formats;
+    }
+
+    /**
+     * Checks if a specific format is supported.
+     * 
+     * @param extension the file extension (e.g., "png", "jpg")
+     * @return true if the format is supported
+     */
+    public static boolean isFormatSupported(String extension) {
+        String ext = extension.toLowerCase();
+        for (ImageFormatProvider provider : providers) {
+            for (String supported : provider.getFileExtensions()) {
+                if (supported.equalsIgnoreCase(ext)) {
+                    return true;
+                }
+            }
+        }
+        return false;
+    }
+}

jhotdraw-core/src/main/java/org/jhotdraw/draw/io/JpegFormatProvider.java

@@ -0,0 +1,64 @@
+/*
+ * @(#)JpegFormatProvider.java
+ *
+ * Copyright (c) 2025 The authors and contributors of JHotDraw.
+ * You may not use, copy or modify this file, except in compliance with the
+ * accompanying license terms.
+ */
+package org.jhotdraw.draw.io;
+
+import org.jhotdraw.draw.figure.ImageHolderFigure;
+import java.awt.image.BufferedImage;
+
+/**
+ * Provider for JPEG (Joint Photographic Experts Group) image format.
+ * 
+ * <p>JPEG uses lossy compression, making it ideal for photographs
+ * and images with smooth color gradients. Supports both .jpg and .jpeg extensions.</p>
+ * 
+ * @author JHotDraw
+ * @version $Id$
+ */
+public class JpegFormatProvider implements ImageFormatProvider {
+
+    @Override
+    public String getFormatName() {
+        return "JPEG";
+    }
+
+    @Override
+    public String getDescription() {
+        return "Joint Photographic Experts Group (JPEG)";
+    }
+
+    @Override
+    public String[] getFileExtensions() {
+        return new String[]{"jpg", "jpeg"};
+    }
+
+    @Override
+    public String[] getMimeTypes() {
+        return new String[]{"image/jpeg", "image/jpg"};
+    }
+
+    @Override
+    public InputFormat createInputFormat(ImageHolderFigure prototype) {
+        return new ImageInputFormat(
+            prototype,
+            getFormatName(),
+            getDescription(),
+            getFileExtensions(),
+            getMimeTypes()
+        );
+    }
+
+    @Override
+    public OutputFormat createOutputFormat() {
+        return new ImageOutputFormat(
+            "JPG",
+            getDescription(),
+            "jpg",
+            BufferedImage.TYPE_INT_RGB
+        );
+    }
+}

jhotdraw-core/src/main/java/org/jhotdraw/draw/io/PngFormatProvider.java

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+/*
+ * @(#)PngFormatProvider.java
+ *
+ * Copyright (c) 2025 The authors and contributors of JHotDraw.
+ * You may not use, copy or modify this file, except in compliance with the
+ * accompanying license terms.
+ */
+package org.jhotdraw.draw.io;
+
+import org.jhotdraw.draw.figure.ImageHolderFigure;
+import java.awt.image.BufferedImage;
+
+/**
+ * Provider for PNG (Portable Network Graphics) image format.
+ * 
+ * <p>PNG supports lossless compression and transparency (alpha channel),
+ * making it ideal for graphics with sharp edges or text.</p>
+ * 
+ * @author JHotDraw
+ * @version $Id$
+ */
+public class PngFormatProvider implements ImageFormatProvider {
+
+    @Override
+    public String getFormatName() {
+        return "PNG";
+    }
+
+    @Override
+    public String getDescription() {
+        return "Portable Network Graphics (PNG)";
+    }
+
+    @Override
+    public String[] getFileExtensions() {
+        return new String[]{"png"};
+    }
+
+    @Override
+    public String[] getMimeTypes() {
+        return new String[]{"image/png"};
+    }
+
+    @Override
+    public InputFormat createInputFormat(ImageHolderFigure prototype) {
+        return new ImageInputFormat(
+            prototype,
+            getFormatName(),
+            getDescription(),
+            getFileExtensions(),
+            getMimeTypes()
+        );
+    }
+
+    @Override
+    public OutputFormat createOutputFormat() {
+        return new ImageOutputFormat(
+            getFormatName(),
+            getDescription(),
+            "png",
+            BufferedImage.TYPE_INT_ARGB
+        );
+    }
+}