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The Apache Commons Codec package contains simple encoder and decoders for various formats such as Base64 and Hexadecimal. In addition to these widely used encoders and decoders, the codec package also maintains a collection of phonetic encoding utilities.
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/*
 *  ====================================================================
 *    Licensed to the Apache Software Foundation (ASF) under one or more
 *    contributor license agreements.  See the NOTICE file distributed with
 *    this work for additional information regarding copyright ownership.
 *    The ASF licenses this file to You under the Apache License, Version 2.0
 *    (the "License"); you may not use this file except in compliance with
 *    the License.  You may obtain a copy of the License at
 *
 *        http://www.apache.org/licenses/LICENSE-2.0
 *
 *    Unless required by applicable law or agreed to in writing, software
 *    distributed under the License is distributed on an "AS IS" BASIS,
 *    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *    See the License for the specific language governing permissions and
 *    limitations under the License.
 * ====================================================================
 */
package org.apache.poi.sl.draw;

import java.awt.Graphics2D;
import java.awt.Insets;
import java.awt.geom.Dimension2D;
import java.awt.geom.Rectangle2D;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.io.InputStream;
import java.nio.charset.Charset;

import org.apache.poi.common.usermodel.GenericRecord;
import org.apache.poi.util.Dimension2DDouble;

/**
 * Classes can implement this interfaces to support other formats, for
 * example, use Apache Batik to render WMF (since POI 4.0, there's an internal WMF/EMF/EMF+ renderer in POI),
 * PICT can be rendered using Apple QuickTime API for Java:
 *
 *  * 
 * public class MyImageRendener implements ImageRendener {
 *     InputStream data;
 *
 *     public boolean drawImage(Graphics2D graphics,Rectangle2D anchor,Insets clip) {
 *         // draw image
 *       DataInputStream is = new DataInputStream(data);
 *       org.apache.batik.transcoder.wmf.tosvg.WMFRecordStore wmfStore =
 *               new org.apache.batik.transcoder.wmf.tosvg.WMFRecordStore();
 *       try {
 *           wmfStore.read(is);
 *       } catch (IOException e){
 *           return;
 *       }
 *
 *       float scale = (float)anchor.width/wmfStore.getWidthPixels();
 *
 *       org.apache.batik.transcoder.wmf.tosvg.WMFPainter painter =
 *               new org.apache.batik.transcoder.wmf.tosvg.WMFPainter(wmfStore, 0, 0, scale);
 *       graphics.translate(anchor.x, anchor.y);
 *       painter.paint(graphics);
 *     }
 *
 *     public void loadImage(InputStream data, String contentType) throws IOException {
 *         if ("image/wmf".equals(contentType)) {
 *             this.data = data;
 *             // use Apache Batik to handle WMF
 *         } else {
 *             super.loadImage(data,contentType);
 *         }
 *     }
 * }
 * 
 * 
 *
 * and then pass this class to your instance of java.awt.Graphics2D:
 *
 *  * 
 * graphics.setRenderingHint(Drawable.IMAGE_RENDERER, new MyImageRendener());
 * 
 * 
 */
public interface ImageRenderer {
    /**
     * Determines if this image renderer implementation supports the given contentType
     * @param contentType the image content type
     * @return if the content type is supported
     */
    boolean canRender(String contentType);

    /**
     * Load and buffer the image
     *
     * @param data the raw image stream
     * @param contentType the content type
     */
    void loadImage(InputStream data, String contentType) throws IOException;

    /**
     * Load and buffer the image
     *
     * @param data the raw image bytes
     * @param contentType the content type
     */
    void loadImage(byte[] data, String contentType) throws IOException;

    /**
     * @return the format-specific / not-normalized bounds of the image
     */
    Rectangle2D getNativeBounds();

    /**
     * @return the bounds of the buffered image in pixel
     */
    Rectangle2D getBounds();

    /**
     * @return the dimension of the buffered image in pixel
     */
    default Dimension2D getDimension() {
        Rectangle2D r = getBounds();
        return new Dimension2DDouble(Math.abs(r.getWidth()), Math.abs(r.getHeight()));
    }

    /**
     * @param alpha the alpha [0..1] to be added to the image (possibly already containing an alpha channel)
     */
    void setAlpha(double alpha);

    /**
     * @return the image as buffered image or null if image could not be loaded
     */
    BufferedImage getImage();

    /**
     * @param dim the dimension in pixels of the returned image
     * @return the image as buffered image or null if image could not be loaded
     *
     * @since POI 3.15-beta2
     */
    BufferedImage getImage(Dimension2D dim);

    /**
     * Render picture data into the supplied graphics
     *
     * @return true if the picture data was successfully rendered
     */
    boolean drawImage(Graphics2D graphics, Rectangle2D anchor);

    /**
     * Render picture data into the supplied graphics
     *
     * @return true if the picture data was successfully rendered
     */
    boolean drawImage(Graphics2D graphics, Rectangle2D anchor, Insets clip);

    default GenericRecord getGenericRecord() { return null; }

    /**
     * Sets the default charset to render text elements.
     * Opposed to other windows libraries in POI this simply defaults to Windows-1252.
     *
     * @param defaultCharset the default charset
     */
    default void setDefaultCharset(Charset defaultCharset) {}
}