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 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

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 * accompanied this code).

 *

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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.

 *

 */

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);

}