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/* * @(#)ImageTranscoder.java 1.20 05/11/17 * * Copyright 2006 Sun Microsystems, Inc. All rights reserved. * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms. */ package javax.imageio; import javax.imageio.metadata.IIOMetadata; /** * An interface providing metadata transcoding capability. * * <p> Any image may be transcoded (written to a different format * than the one it was originally stored in) simply by performing * a read operation followed by a write operation. However, loss * of data may occur in this process due to format differences. * * <p> In general, the best results will be achieved when * format-specific metadata objects can be created to encapsulate as * much information about the image and its associated metadata as * possible, in terms that are understood by the specific * <code>ImageWriter</code> used to perform the encoding. * * <p> An <code>ImageTranscoder</code> may be used to convert the * <code>IIOMetadata</code> objects supplied by the * <code>ImageReader</code> (representing per-stream and per-image * metadata) into corresponding objects suitable for encoding by a * particular <code>ImageWriter</code>. In the case where the methods * of this interface are being called directly on an * <code>ImageWriter</code>, the output will be suitable for that * writer. * * <p> The internal details of converting an <code>IIOMetadata</code> * object into a writer-specific format will vary according to the * context of the operation. Typically, an <code>ImageWriter</code> * will inspect the incoming object to see if it implements additional * interfaces with which the writer is familiar. This might be the * case, for example, if the object was obtained by means of a read * operation on a reader plug-in written by the same vendor as the * writer. In this case, the writer may access the incoming object by * means of its plug-in specific interfaces. In this case, the * re-encoding may be close to lossless if the image file format is * kept constant. If the format is changing, the writer may still * attempt to preserve as much information as possible. * * <p> If the incoming object does not implement any additional * interfaces known to the writer, the writer has no choice but to * access it via the standard <code>IIOMetadata</code> interfaces such * as the tree view provided by <code>IIOMetadata.getAsTree</code>. * In this case, there is likely to be significant loss of * information. * * <p> An independent <code>ImageTranscoder</code> essentially takes * on the same role as the writer plug-in in the above examples. It * must be familiar with the private interfaces used by both the * reader and writer plug-ins, and manually instantiate an object that * will be usable by the writer. The resulting metadata objects may * be used by the writer directly. * * <p> No independent implementations of <code>ImageTranscoder</code> * are provided as part of the standard API. Instead, the intention * of this interface is to provide a way for implementations to be * created and discovered by applications as the need arises. * * @version 0.5 */ public interface ImageTranscoder { /** * Returns an <code>IIOMetadata</code> object that may be used for * encoding and optionally modified using its document interfaces * or other interfaces specific to the writer plug-in that will be * used for encoding. * * <p> An optional <code>ImageWriteParam</code> may be supplied * for cases where it may affect the structure of the stream * metadata. * * <p> If the supplied <code>ImageWriteParam</code> contains * optional setting values not understood by this writer or * transcoder, they will be ignored. * * @param inData an <code>IIOMetadata</code> object representing * stream metadata, used to initialize the state of the returned * object. * @param param an <code>ImageWriteParam</code> that will be used to * encode the image, or <code>null</code>. * * @return an <code>IIOMetadata</code> object, or * <code>null</code> if the plug-in does not provide metadata * encoding capabilities. * * @exception IllegalArgumentException if <code>inData</code> is * <code>null</code>. */ IIOMetadata convertStreamMetadata(IIOMetadata inData, ImageWriteParam param); /** * Returns an <code>IIOMetadata</code> object that may be used for * encoding and optionally modified using its document interfaces * or other interfaces specific to the writer plug-in that will be * used for encoding. * * <p> An optional <code>ImageWriteParam</code> may be supplied * for cases where it may affect the structure of the image * metadata. * * <p> If the supplied <code>ImageWriteParam</code> contains * optional setting values not understood by this writer or * transcoder, they will be ignored. * * @param inData an <code>IIOMetadata</code> object representing * image metadata, used to initialize the state of the returned * object. * @param imageType an <code>ImageTypeSpecifier</code> indicating * the layout and color information of the image with which the * metadata will be associated. * @param param an <code>ImageWriteParam</code> that will be used to * encode the image, or <code>null</code>. * * @return an <code>IIOMetadata</code> object, * or <code>null</code> if the plug-in does not provide * metadata encoding capabilities. * * @exception IllegalArgumentException if either of * <code>inData</code> or <code>imageType</code> is * <code>null</code>. */ IIOMetadata convertImageMetadata(IIOMetadata inData, ImageTypeSpecifier imageType, ImageWriteParam param); }