1/*
2 * Copyright (c) 2000, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
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7 * published by the Free Software Foundation.  Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
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24 */
25
26package javax.imageio;
27
28import javax.imageio.metadata.IIOMetadata;
29
30/**
31 * An interface providing metadata transcoding capability.
32 *
33 * <p> Any image may be transcoded (written to a different format
34 * than the one it was originally stored in) simply by performing
35 * a read operation followed by a write operation.  However, loss
36 * of data may occur in this process due to format differences.
37 *
38 * <p> In general, the best results will be achieved when
39 * format-specific metadata objects can be created to encapsulate as
40 * much information about the image and its associated metadata as
41 * possible, in terms that are understood by the specific
42 * {@code ImageWriter} used to perform the encoding.
43 *
44 * <p> An {@code ImageTranscoder} may be used to convert the
45 * {@code IIOMetadata} objects supplied by the
46 * {@code ImageReader} (representing per-stream and per-image
47 * metadata) into corresponding objects suitable for encoding by a
48 * particular {@code ImageWriter}.  In the case where the methods
49 * of this interface are being called directly on an
50 * {@code ImageWriter}, the output will be suitable for that
51 * writer.
52 *
53 * <p> The internal details of converting an {@code IIOMetadata}
54 * object into a writer-specific format will vary according to the
55 * context of the operation.  Typically, an {@code ImageWriter}
56 * will inspect the incoming object to see if it implements additional
57 * interfaces with which the writer is familiar.  This might be the
58 * case, for example, if the object was obtained by means of a read
59 * operation on a reader plug-in written by the same vendor as the
60 * writer.  In this case, the writer may access the incoming object by
61 * means of its plug-in specific interfaces.  In this case, the
62 * re-encoding may be close to lossless if the image file format is
63 * kept constant.  If the format is changing, the writer may still
64 * attempt to preserve as much information as possible.
65 *
66 * <p> If the incoming object does not implement any additional
67 * interfaces known to the writer, the writer has no choice but to
68 * access it via the standard {@code IIOMetadata} interfaces such
69 * as the tree view provided by {@code IIOMetadata.getAsTree}.
70 * In this case, there is likely to be significant loss of
71 * information.
72 *
73 * <p> An independent {@code ImageTranscoder} essentially takes
74 * on the same role as the writer plug-in in the above examples.  It
75 * must be familiar with the private interfaces used by both the
76 * reader and writer plug-ins, and manually instantiate an object that
77 * will be usable by the writer.  The resulting metadata objects may
78 * be used by the writer directly.
79 *
80 * <p> No independent implementations of {@code ImageTranscoder}
81 * are provided as part of the standard API.  Instead, the intention
82 * of this interface is to provide a way for implementations to be
83 * created and discovered by applications as the need arises.
84 *
85 */
86public interface ImageTranscoder {
87
88    /**
89     * Returns an {@code IIOMetadata} object that may be used for
90     * encoding and optionally modified using its document interfaces
91     * or other interfaces specific to the writer plug-in that will be
92     * used for encoding.
93     *
94     * <p> An optional {@code ImageWriteParam} may be supplied
95     * for cases where it may affect the structure of the stream
96     * metadata.
97     *
98     * <p> If the supplied {@code ImageWriteParam} contains
99     * optional setting values not understood by this writer or
100     * transcoder, they will be ignored.
101     *
102     * @param inData an {@code IIOMetadata} object representing
103     * stream metadata, used to initialize the state of the returned
104     * object.
105     * @param param an {@code ImageWriteParam} that will be used to
106     * encode the image, or {@code null}.
107     *
108     * @return an {@code IIOMetadata} object, or
109     * {@code null} if the plug-in does not provide metadata
110     * encoding capabilities.
111     *
112     * @exception IllegalArgumentException if {@code inData} is
113     * {@code null}.
114     */
115    IIOMetadata convertStreamMetadata(IIOMetadata inData,
116                                      ImageWriteParam param);
117
118    /**
119     * Returns an {@code IIOMetadata} object that may be used for
120     * encoding and optionally modified using its document interfaces
121     * or other interfaces specific to the writer plug-in that will be
122     * used for encoding.
123     *
124     * <p> An optional {@code ImageWriteParam} may be supplied
125     * for cases where it may affect the structure of the image
126     * metadata.
127     *
128     * <p> If the supplied {@code ImageWriteParam} contains
129     * optional setting values not understood by this writer or
130     * transcoder, they will be ignored.
131     *
132     * @param inData an {@code IIOMetadata} object representing
133     * image metadata, used to initialize the state of the returned
134     * object.
135     * @param imageType an {@code ImageTypeSpecifier} indicating
136     * the layout and color information of the image with which the
137     * metadata will be associated.
138     * @param param an {@code ImageWriteParam} that will be used to
139     * encode the image, or {@code null}.
140     *
141     * @return an {@code IIOMetadata} object,
142     * or {@code null} if the plug-in does not provide
143     * metadata encoding capabilities.
144     *
145     * @exception IllegalArgumentException if either of
146     * {@code inData} or {@code imageType} is
147     * {@code null}.
148     */
149    IIOMetadata convertImageMetadata(IIOMetadata inData,
150                                     ImageTypeSpecifier imageType,
151                                     ImageWriteParam param);
152}
153