--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/jdk/src/share/classes/javax/imageio/metadata/doc-files/jpeg_metadata.html Sat Dec 01 00:00:00 2007 +0000
@@ -0,0 +1,1148 @@
+<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN">
+<html>
+<head>
+<!--
+Copyright 2000-2001 Sun Microsystems, Inc. All Rights Reserved.
+DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+
+This code is free software; you can redistribute it and/or modify it
+under the terms of the GNU General Public License version 2 only, as
+published by the Free Software Foundation. Sun designates this
+particular file as subject to the "Classpath" exception as provided
+by Sun in the LICENSE file that accompanied this code.
+
+This code is distributed in the hope that it will be useful, but WITHOUT
+ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
+version 2 for more details (a copy is included in the LICENSE file that
+accompanied this code).
+
+You should have received a copy of the GNU General Public License version
+2 along with this work; if not, write to the Free Software Foundation,
+Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+
+Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
+CA 95054 USA or visit www.sun.com if you need additional information or
+have any questions.
+-->
+
+<title>JPEG Metadata Format Specification and Usage Notes</title>
+</head>
+
+<body bgcolor="white">
+
+<center><h1>
+JPEG Metadata Format Specification and Usage Notes
+</h1></center>
+
+<p>
+<a href=#metadata>JPEG Metadata</a><br>
+<a href=#abbrev>Abbreviated Streams</a><br>
+<a href=#tables>Sources of Tables</a><br>
+<a href=#color>Colorspace Transformations and Conventional Markers</a><br>
+<a href=#thumbs>Thumbnail Images</a><br>
+<a href=#prog>Progressive Encoding</a><br>
+<a href=#tree>Native Metadata Format Tree Structure and Editing</a><br>
+<a href=#image>Image Metadata DTD</a><br>
+<a href=#stream>Stream Metadata DTD</a>
+<p>
+<bold>NOTE</bold>: It is important to call <code>dispose()</code>
+on the JPEG reader and writer objects when they are no longer needed, as
+they consume significant native resources which are not adequately recovered
+by garbage collection. Both reader and writer call <code>dispose()</code>
+in their finalizers, but those finalizers may not be called before the native
+code has exhausted native memory.
+
+<p>
+
+The JPEG writer does not support replacing pixels.
+
+<p>
+<h2>
+<a name=metadata>JPEG Metadata</a>
+</h2>
+JPEG metadata consists of the data contained in marker segments in a JPEG
+stream. The image metadata object returned from a read describes the
+contents of the marker segments between the <code>SOI</code> marker and
+the <code>EOI</code> marker for that image. The image metadata object
+passed into a write determines the contents of the stream between the
+<code>SOI</code> marker and the <code>EOI</code> marker for that image,
+subject to the controls in any <code>ImageWriteParam</code>.
+
+<p>
+Stream metadata is used only for tables-only images found (or to be
+placed) at the beginning of a stream containing abbreviated images.
+Tables-only images are not treated as images and do not consume an
+image index. The stream metadata object returned from a read describes the
+contents of the marker segments between the <code>SOI</code> marker and
+the <code>EOI</code> marker for the single tables-only image at the
+beginning of the stream, if one is present. If no tables-only image is
+present at the front of the stream, the <code>getStreamMetadata</code>
+method of <code>ImageReader</code> returns <code>null</code>. If
+stream metadata is provided to the writer, a single tables-only image
+containing the tables from the stream metadata object will be written at
+the beginning of the stream. If the stream metadata object contains no
+tables, default tables will be written. As the sole purpose of stream
+metadata is for specifying tables-only images at the front of abbreviated
+streams, the stream metadata argument is useful only on the
+<code>ImageWriter.prepareWriteSequence</code> method. It is ignored on all
+other methods.
+
+<p>
+The <code>ImageWriter.getDefaultStreamMetadata</code> method returns an
+object containing the tables from the <code>ImageWriteParam</code> argument,
+if it is a <code>JPEGImageWriteParam</code> and contains tables. Otherwise,
+the returned object will contain default tables.
+
+<p>The <code>ImageWriter.getDefaultImageMetadata</code> method returns a
+metadata object containing <bold>no</bold> tables if the
+<code>ImageWriteParam</code> argument contains tables. Otherwise the
+returned metadata object will contain default visually lossless tables.
+Of course, only a <code>JPEGImageWriteParam</code> may contain tables.
+
+<p>
+If <code>ignoreMetadata</code> is set to <code>true</code> when the input
+is set on the reader, stream metadata will not be available, but image
+metadata will.
+
+<p>
+<h2>
+<a name=abbrev>Abbreviated Streams</a>
+</h2>
+Both the reader and the writer retain their tables from one operation to the
+next, thus permitting the use of abbreviated streams quite naturally, with a
+few minor restrictions:
+<ol>
+ <li> Abbreviated streams may contain only one tables-only image, which must
+ come first in the stream. Subsequent tables-only images will cause
+ undefined behavior.</li>
+ <li> Abbreviated streams must be read fully and in order. No random access
+ is allowed, in either direction. The same image may be read multiple
+ times. If a call is made with an image index that is not the same as
+ or one greater than the most recent call (or 0 if no calls have been
+ made), then an <code>IllegalArgumentException</code> is thrown.</li>
+</ol>
+These restrictions mean that streams may contain abbreviated images
+interspersed with images containing tables. As required by JPEG, any tables
+appearing in the stream override previous tables, regardless of the source
+of the previous tables.
+
+<p>
+Note that once a tables-only image has been read, it's contents is available
+as stream metadata from the reader until either another tables-only image
+is read from another stream or the reader is reset. Changing the input does
+not reset the stream metadata. This is useful for reading the tables from
+one file, then changing the input to read an abbreviated stream containing
+a sequence of images. The tables will be used automatically, and will remain
+available as "stream" metadata.
+
+<p>
+Abbreviated streams are written using the sequence methods of
+<code>ImageWriter</code>. Stream metadata is used to write a tables-only
+image at the beginning of the stream, and the tables are set up for use, using
+<code>ImageWriter.prepareWriteSequence</code>. If no stream metadata is
+supplied to <code>ImageWriter.prepareWriteSequence</code>, then no
+tables-only image is written. If stream metadata containing no tables is
+supplied to <code>ImageWriter.prepareWriteSequence</code>, then a tables-only
+image containing default visually lossless tables is written.
+
+<h2>
+<a name=tables>Sources of Tables</a>
+</h2>
+<p>
+Images are written with tables if tables are present in their metadata objects
+or without them if no tables are present in their metadata objects. If no
+metadata object is present then the tables are written. The tables used for
+compression are taken from one of the following sources, which are consulted
+in order:
+<ol>
+ <li> If there is an <code>ImageWriteParam</code> and the compression mode is
+ set to <code>EXPLICIT</code>, default tables constructed using the
+ quality setting are used. They are written only if the metadata
+ contains tables or if there is no metadata, but they replace the
+ tables in the metadata.</li>
+ <li> If there is an <code>ImageWriteParam</code> and the compression mode is
+ set to <code>DEFAULT</code>, default visually lossles tables are used.
+ They are written only if the metadata contains tables or if
+ there is no metadata, but they replace the tables in the
+ metadata.</li>
+ <li> Otherwise the compression mode on the <code>ImageWriteParam</code> must
+ be MODE_COPY_FROM_<code>METADATA</code>, in which case the following
+ are used:
+ <ol>
+ <li> the tables in the image metadata, if present</li>
+ <li> the tables in the stream metadata, if present</li>
+ <li> the tables in the <code>JPEGImageWriteParam</code>, if present</li>
+ <li> default visually lossless tables</li>
+ </ol> Tables are written only if they are taken from image metadata.
+ </li>
+</ol>
+
+This ordering implements the design intention that tables should be included
+in <code>JPEGImageWriteParam</code>s only as a means of specifying tables
+when no other source is available, and this can occur only when writing to an
+abbreviated stream without tables using known non-standard tables for
+compression.
+
+<p>
+When reading, tables in a <code>JPEGImageReadParam</code> are consulted only
+if tables have not been set by any previous read. Tables set from a
+<code>JPEGImageReadParam</code> are overridden by any tables present in the
+stream being read.
+
+<p>
+Note that if no image metadata object is specified for a particular image, a
+default object is used, which includes default tables.
+
+<p>
+<h2>
+<a name=color>Colorspace Transformations and Conventional Markers</a>
+</h2>
+Colorspace transformations are controlled by the destination type for
+both reading and writing of images. When <code>Raster</code>s are
+read, no colorspace transformation is performed, and any destination type
+is ignored. A warning is sent to any listeners if a destination type is
+specified in this case. When <code>Raster</code>s are written, any
+destination type is used to interpret the bands. This might result in a
+JFIF or Adobe header being written, or different component ids being written
+to the frame and scan headers. If values present in a metadata object do not
+match the destination type, the destination type is used and a warning is sent
+to any listeners.
+
+<p>
+
+When reading, the contents of the stream are interpreted by the usual
+JPEG conventions, as follows:
+
+<ul>
+ <li> If a JFIF <code>APP0</code> marker segment is present, the colorspace
+ is known to be either grayscale or YCbCr. If an <code>APP2</code>
+ marker segment containing an embedded ICC profile is also present, then
+ the YCbCr is converted to RGB according to the formulas given in the
+ JFIF spec, and the ICC profile is assumed to refer to the resulting RGB
+ space.
+ <p>
+ <li> If an Adobe <code>APP14</code> marker segment is present, the
+ colorspace is determined by consulting the <code>transform</code> flag.
+ The <code>transform</code> flag takes one of three values:
+ <ul>
+ <li> 2 - The image is encoded as YCCK (implicitly converted from
+ CMYK on encoding).
+
+ <li> 1 - The image is encoded as YCbCr (implicitly converted from RGB
+ on encoding).
+
+ <li> 0 - Unknown. 3-channel images are assumed to be RGB, 4-channel
+ images are assumed to be CMYK.
+ </ul>
+ <p>
+ <li> If neither marker segment is present, the following procedure is
+ followed: Single-channel images are assumed to be grayscale, and
+ 2-channel images are assumed to be grayscale with an alpha channel.
+ For 3- and 4-channel images, the component ids are consulted. If these
+ values are 1-3 for a 3-channel image, then the image is assumed to be
+ YCbCr. If these values are 1-4 for a 4-channel image, then the image
+ is assumed to be YCbCrA. If these values are > 4, they are checked
+ against the ASCII codes for 'R', 'G', 'B', 'A', 'C', 'c'. These can
+ encode the following colorspaces:
+ <p>
+ <br>RGB
+ <br>RGBA
+ <br>YCC (as 'Y','C','c'), assumed to be PhotoYCC
+ <br>YCCA (as 'Y','C','c','A'), assumed to be PhotoYCCA
+ <p>
+ Otherwise, 3-channel subsampled images are assumed to be YCbCr,
+ 3-channel non-subsampled images are assumed to be RGB, 4-channel
+ subsampled images are assumed to be YCCK, and 4-channel, non-subsampled
+ images are assumed to be CMYK.
+
+ <p>
+ <li> All other images are declared uninterpretable and an exception is
+ thrown if an attempt is made to read one as a
+ <code>BufferedImage</code>. Such an image may be read only as a
+ <code>Raster</code>. If an image is interpretable but there is no Java
+ <code>ColorSpace</code> available corresponding to the encoded
+ colorspace (<italic>e.g.</italic> YCbCr), then
+ <code>ImageReader.getRawImageType</code> will return <code>null</code>.
+</ul>
+
+Once an encoded colorspace is determined, then the target colorspace is
+determined as follows:
+
+<ul>
+ <li> If a destination type is not set, then the following default
+ transformations take place after upsampling: YCbCr (and YCbCrA) images
+ are converted to RGB (and RGBA) using the conversion provided by the
+ underlying IJG library and either the built-in sRGB
+ <code>ColorSpace</code> or a custom RGB <code>ColorSpace</code> object
+ based on an embedded ICC profile is used to create the output
+ <code>ColorModel</code>. PhotoYCC and PhotoYCCA images are not
+ converted. CMYK and YCCK images are currently not supported.</li>
+
+ <li> If a destination image or type is set, it is used as follows:
+ If the IJG library provides an appropriate conversion, it is used.
+ Otherwise the default library conversion is followed by a colorspace
+ conversion in Java.</li>
+
+ <li> Bands are selected AFTER any library colorspace conversion. If a
+ subset of either source or destination bands is used, then the default
+ library conversions are used with no further conversion in Java,
+ regardless of any destination type.</li>
+
+ <li> An exception is thrown if an attempt is made to read an image in an
+ unsupported jpeg colorspace as a <code>BufferedImage</code>
+ (<italic>e.g.</italic> CMYK). Such images may be read as
+ <code>Raster</code>s. If an image colorspace is unsupported or
+ uninterpretable, then <code>ImageReader.getImageTypes</code> will
+ return an empty <code>Iterator</code>. If a subset of the raw bands
+ are required, a <code>Raster</code> must be obtained first and the
+ bands obtained from that. </li>
+</ul>
+
+<p>
+For writing, the color transformation to apply is determined as
+follows:
+
+<p>
+If a subset of the source bands is to be written, no color conversion is
+performed. Any destination, if set, must match the number of bands that will
+be written, and serves as an interpretation of the selected bands, rather than
+a conversion request. This behavior is identical to that for
+<code>Raster</code>s. If all the bands are to be written and an image
+(as opposed to a <code>Raster</code>) is being written, any destination type
+is ignored and a warning is sent to any listeners.
+
+<p>
+If a destination type is used and any aspect of the metadata object, if there
+is one, is not compatible with that type, the destination type is used, the
+metadata written is modified from that provided, and a warning is sent to
+listeners. This includes the <code>app0JFIF</code> and
+<code>app14Adobe</code> nodes. The component ids in the <code>sof</code> and
+<code>sos</code> nodes are not modified, however, as unless a
+<code>app0JFIF</code> node is present, any values may be used.
+<p>
+
+When a full image is written, a destination colorspace will be
+chosen based on the image contents and the metadata settings, according to
+the following algorithm:
+
+<p>
+
+If no metadata object is specified, then the following defaults apply:
+
+<ul>
+ <li> Grayscale images are written with a JFIF <code>APP0</code> marker
+ segment. Grayscale images with alpha are written with no special
+ marker. As required by JFIF, the component ids in the frame and
+ scan header is set to 1.
+
+ <li> RGB images are converted to YCbCr, subsampled in the chrominance
+ channels by half both vertically and horizontally, and written with a
+ JFIF <code>APP0</code> marker segment. If the <code>ColorSpace</code>
+ of the image is based on an <code>ICCProfile</code> (it is an instance
+ of <code>ICC_ColorSpace</code>, but is not one of the standard built-in
+ <code>ColorSpaces</code>), then that profile is embedded in an
+ <code>APP2</code> marker segment. As required by JFIF, the
+ component ids in the frame and scan headers are set to 1, 2, and 3.
+
+
+ <li> RGBA images are converted to YCbCrA, subsampled in the
+ chrominance channels by half both vertically and horizontally, and
+ written without any special marker segments. The component ids
+ in the frame and scan headers are set to 1, 2, 3, and 4.
+
+ <li> PhotoYCC and YCCAimages are subsampled by half in the chrominance
+ channels both vertically and horizontally and written with an
+ Adobe <code>APP14</code> marker segment and 'Y','C', and 'c' (and
+ 'A' if an alpha channel is present) as component ids in the frame
+ and scan headers.
+</ul>
+
+Default metadata objects for these image types will reflect these settings.
+
+<p>
+
+If a metadata object is specified, then the number of channels in the
+frame and scan headers must always match the number of bands to be
+written, or an exception is thrown. <code>app0JFIF</code> and
+<code>app14Adobe</code> nodes may appear in the same metadata object only
+if the <code>app14Adobe</code> node indicates YCbCr, and the component ids
+are JFIF compatible (0-2). The various image types are processed in the
+following ways:
+
+<br>
+
+(All multi-channel images are subsampled according to the sampling factors
+in the frame header node of the metadata object, regardless of color space.)
+
+<ul>
+ <li> Grayscale Images:
+ <ul>
+ <li> If an <code>app0JFIF</code> node is present in the metadata object,
+ a JFIF <code>APP0</code> marker segment is written.
+ <li> If an <code>app14Adobe</code> node is present in the metadata
+ object, it is checked for validity (<code>transform</code> must be
+ <code>UNKNOWN</code>) and written.
+ <li> If neither node is present in the metadata object, no special
+ marker segment is written.
+ </ul>
+
+ <li> Grayscale Images with an Alpha Channel:
+ <ul>
+ <li> If an <code>app0JFIF</code> node is present in the metadata object,
+ it is ignored and a warning is sent to listeners, as JFIF does not
+ support 2-channel images.
+ <li> If an <code>app14Adobe</code> node is present in the metadata
+ object, it is checked for validity (<code>transform</code> must be
+ <code>UNKNOWN</code>) and written. If <code>transform</code> is
+ not <code>UNKNOWN</code>, a warning is sent to listeners and the
+ correct transform is written.
+ <li> If neither node is present in the metadata object, no special
+ marker segment is written.
+ </ul>
+
+ <li> RGB Images:
+ <ul>
+ <li> If an <code>app0JFIF</code> node is present in the metadata object,
+ the image is converted to YCbCr and written with a JFIF
+ <code>APP0</code> marker segment. If the <code>ColorSpace</code>
+ of the image is based on a non-standard ICC Profile, then that
+ profile is embedded in an <code>APP2</code> marker segment. If the
+ <code>ColorSpace</code> is not based on a non-standard ICC Profile,
+ but an <code>app2ICC</code> node appears in the metadata, then an
+ <code>APP2</code> marker segment is written with the appropriate
+ standard profile. Note that the profile must specify an RGB color
+ space, as the file must be JFIF compliant.
+
+ <li> If an <code>app14Adobe</code> node is present in the metadata
+ object, the image is converted according to the color transform
+ setting and written with an Adobe <code>APP14</code> marker
+ segment. Component ids are written just as they appear in the
+ frame and scan headers. The color transform must be either YCbCr
+ or <code>UNKNOWN</code>. If it is <code>UNKNOWN</code>, the image
+ is not color converted.
+
+ <li> If neither node is present, the component ids in the frame
+ header are consulted. If these indicate a colorspace as described
+ above, then the image is converted to that colorspace if possible.
+ If the component ids do not indicate a colorspace, then the
+ sampling factors are consulted. If the image is to be subsampled,
+ it is converted to YCbCr first. If the image is not to be
+ subsampled, then no conversion is applied. No special marker
+ segmentss are written.
+ </ul>
+
+ <li> RGBA images:
+ <ul>
+ <li> If an <code>app0JFIF</code> node is present in the metadata object,
+ it is ignored and a warning is sent to listeners, as JFIF does not
+ support 4-channel images.
+
+ <li> If an <code>app14Adobe</code> node is present in the metadata
+ object, the image is written with an Adobe <code>APP14</code> marker
+ segment. No colorspace conversion is performed. Component ids
+ are written just as they appear in the frame and scan headers.
+ The color transform must be <code>UNKNOWN</code>. If it is
+ not, a warning is sent to listeners.
+
+ <li> If no <code>app14Adobe</code> node is present, the component ids in
+ the frame header are consulted. If these indicate a colorspace as
+ described above, then the image is converted to that colorspace if
+ possible. If the component ids do not indicate a colorspace, then
+ the sampling factors are consulted. If the image is to be
+ subsampled, it is converted to YCbCrA. If the image is not to be
+ subsampled, then no conversion is applied. No special marker
+ segments are written.
+ </ul>
+
+ <li> PhotoYCC Images:
+ <ul>
+ <li> If an <code>app0JFIF</code> node is present in the metadata object,
+ the image is converted to sRGB, and then to YCbCr during encoding,
+ and a JFIF <code>APP0</code> marker segment is written.
+
+ <li> If an <code>app14Adobe</code> node is present in the metadata
+ object, no conversion is applied, and an Adobe <code>APP14</code>
+ marker segment is written. The color transform must be YCC. If it
+ is not, a warning is sent to listeners.
+
+ <li> If neither node is present in the metadata object, no conversion
+ is applied, and no special marker segment is written.
+ </ul>
+
+ <li> PhotoYCCA Images:
+ <ul>
+ <li> If an <code>app0JFIF</code> node is present in the metadata object,
+ it is ignored and a warning is sent to listeners, as JFIF does not
+ support 4-channel images.
+
+ <li> If an <code>app14Adobe</code> node is present in the metadata
+ object, no conversion is applied, and an Adobe <code>APP14</code>
+ marker segment is written. The color transform must be
+ <code>UNKNOWN</code>. If it is not, a warning is sent to
+ listeners.
+
+ <li> If neither node is present in the metadata object, no conversion
+ is applied, and no special marker segment is written.
+ </ul>
+</ul>
+
+<p>
+<h2>
+<a name=thumbs>Thumbnail Images</a>
+</h2>
+Thumbnails are supported by the use of JFIF and JFIF extension marker segments.
+Thumbnails provided on the write methods determine the thumbnails that will be
+included. <code>app0JFIF</code> and <code>app0JFXX</code> nodes present in
+the metadata do not contain any thumbnail pixel data. However, the kinds of
+thumbnails written depend on the contents of the metadata object, as follows.
+Any thumbnail which is to be written as an indexed or RGB image and which is
+larger than 255 by 255 will be clipped, not scaled, to 255 by 255. Thumbnails
+written as JPEG images may be any size. A warning is sent to any listeners
+whenever a thumbnail is clipped.
+<ul>
+ <li> If there is a single thumbnail, it is processed as follows:
+ <ul>
+ <li> If the thumbnail image is an RGB palette image, it is processed as
+ follows:
+ <ul>
+ <li> If no <code>app0JFXX</code> node is present in the metadata, or
+ the first <code>app0JFXX</code> node present in the metadata
+ contains a <code>JFIFthumbPalette</code> element, a
+ palette thumbnail is written in a JFXX <code>APP0</code> marker
+ segment.
+ <li> If the first <code>app0JFXX</code> node present in the metadata
+ contains another thumbnail form (RGB or JPEG), the palette
+ image is expanded to RGB and the indicated thumbnail form is
+ written.
+ </ul>
+
+ <li> If the thumbnail image is an RGB image, it is processed as follows:
+ <ul>
+ <li> If no <code>app0JFXX</code> node is present in the metadata,
+ the thumbnail is written as part of the JFIF <code>APP0</code>
+ marker segment.
+ <li> If the first <code>app0JFXX</code> node present in the metadata
+ contains a <code>JFIFthumbRGB</code> element, an
+ RGB thumbnail is written in a JFXX <code>APP0</code> marker
+ segment.
+ <li> If the first <code>app0JFXX</code> node present in the metadata
+ contains a <code>JFIFthumbJPEG</code> element, a
+ JPEG thumbnail is written in a JFXX <code>APP0</code> marker
+ segment.
+ <li> If the first <code>app0JFXX</code> node present in the metadata
+ contains a <code>JFIFthumbPalette</code> element, an
+ RGB thumbnail is written in a JFXX <code>APP0</code> marker
+ segment and a warning is sent to any listeners.
+ </ul>
+
+ <li> If the thumbnail image is a grayscale image, it is processed as
+ follows:
+ <ul>
+ <li> If no <code>app0JFXX</code> node is present in the metadata,
+ the thumbnail is expanded to RGB and written as part of the
+ JFIF <code>APP0</code> marker segment.
+ <li> If the first <code>app0JFXX</code> node present in the metadata
+ contains a <code>JFIFthumbRGB</code> element, the thumbnail is
+ expanded to RGB and written in a separate <code>JFXX</code> RGB
+ marker segment.
+ <li> If the first <code>app0JFXX</code> node present in the metadata
+ contains a <code>JFIFthumbJPEG</code> element, a
+ JPEG thumbnail is written in a JFXX <code>APP0</code> marker
+ segment.
+ <li> If the first <code>app0JFXX</code> node present in the metadata
+ contains a <code>JFIFthumbPalette</code> element, a
+ JPEG thumbnail is written in a JFXX <code>APP0</code> marker
+ segment and a warning is sent to any listeners.
+ </ul>
+
+ <li> Any other thumbnail image types are ignored and a warning is sent
+ to any listeners.
+ </ul>
+
+ <li> If there are multiple thumbnails, each one is processed as above, except
+ that no thumbnail is placed in the JFIF <code>APP0</code> segment, and
+ the <code>app0JFXX</code> node consulted for each thumbnail is the
+ <code>app0JFXX</code> node from the metadata that occurs in the same
+ sequence as the thumbnail. <italic>I.e.</italic> the first
+ <code>app0JFXX</code> node applies to the first thumbnail, the second
+ node to the second thumbnail, and so on. If there are fewer
+ <code>app0JFXX</code> nodes in the metadata than thumbnails, then
+ those thumbnails are considered to have no matching
+ <code>app0JFXX</code> node. An RGB thumbnail with no matching
+ <code>app0JFXX</code> node is written in a JFXX <code>APP0</code> marker
+ segment. A grayscale thumbnail with no matching
+ <code>app0JFXX</code> node is written as a JPEG image to a JFXX
+ <code>APP0</code> marker segment.
+</ul>
+<p>
+
+Note that as the only mechanism for storing thumbnails is via the
+JFIF or JFIF extension marker segments, only grayscale or RGB images
+may have thumbnails. If thumbnails are present when writing any other type
+of image, the thumbnails are ignored and a warning is sent to any warning
+listeners.
+
+<p>
+<h2>
+<a name=prog>Progressive Encoding</a>
+</h2>
+
+Progressive encoding must be enabled on the <code>ImageWriteParam</code>
+passed in to a write operation, or the image will be written sequentially,
+regardless of the scan headers included in the metadata object. If
+progressive encoding is enabled and set to copy from metadata, then
+the sequence of scan headers from the metadata is used to write the
+image. If progressive encoding is enabled and set to use a default,
+then the scans in the metadata are ignored and a default set of scans
+is used. Progressive encoding always forces optimized Huffman tables to
+be used. Any Huffman tables present in the metadata will be ignored,
+and a warning will be sent to any warning listeners.
+
+If Huffman-table optimization is requested on the <code>ImageWriteParam</code>,
+all Huffman tables in the metadata or in the <code>ImageWriteParam</code>
+itself are ignored, and a warning will be sent to any warning listeners if
+any such tables are present.
+
+<p>
+<h2>
+<a name=tree>Native Metadata Format Tree Structure and Editing</a>
+</h2>
+
+The DTDs below describe just the trees of metadata objects actually returned
+by the <code>IIOMetadata</code> object. They do not include nodes
+corresponding to <code>SOI</code>, <code>EOI</code>, or <code>RST</code>
+markers, as these parsing delimiters do not carry any meaningful metadata.
+<p>
+
+The first node is always a <code>JPEGvariety</code> node. In the
+<code>javax_imageio_jpeg_image_1.0</code> version of the JPEG metadata
+format, this node may have one child, an <code>app0JFIF</code> node,
+indicating that the JPEG stream contains a JFIF marker segment and related
+data, or no children, indicating that the stream contains no JFIF marker.
+In future versions of the JPEG metadata format, other varieties of JPEG
+metadata may be supported (e.g. Exif) by defining other types of nodes
+which may appear as a child of the <code>JPEGvariety</code> node.
+<p>
+
+(Note that an application wishing to interpret Exif metadata given
+a metadata tree structure in the <code>javax_imageio_jpeg_image_1.0</code>
+format must check for an <code>unknown</code> marker segment with a tag
+indicating an <code>APP1</code> marker and containing data identifying it
+as an Exif marker segment. Then it may use application-specific code to
+interpret the data in the marker segment. If such an application were
+to encounter a metadata tree formatted according to a future version of
+the JPEG metadata format, the Exif marker segment might not be
+<code>unknown</code> in that format - it might be structured as a
+child node of the <code>JPEGvariety</code> node. Thus, it is important
+for an application to specify which version to use by passing the string
+identifying the version to the method/constructor used to obtain an
+<code>IIOMetadata</code> object.)
+
+<p>
+
+On reading, <code>JFXX</code> and <code>app2ICC</code> nodes occur as
+children of an <code>app0JFIF</code> node.
+This is true regardless of where the JFXX <code>APP0</code> and
+<code>APP2</code> marker segments actually occur in the stream. The ordering
+of nodes within the <code>markerSequence</code> node corresponds to the
+ordering of marker segments found in the JPEG stream.
+<p>
+On writing, any <code>JFXX</code> and <code>app2ICC</code> nodes must
+occur as children of an <code>app0JFIF</code> node, itself a child of a
+<code>JPEGvariety</code> node, which must always be the first node.
+(If the stream is not to be JFIF compliant, no <code>app0JFIF</code> node
+should be provided, and the <code>JPEGvariety</code> node should have no
+children.) Any
+JFIF <code>APP0</code>, JFXX <code>APP0</code>, and <code>APP2</code> marker
+segments are written first, followed by all Adobe <code>APP14</code>,
+<code>APPn</code>, <code>COM</code> and unknown segments in the
+order in which their corresponding nodes appear in the
+<code>markerSequence</code> node, followed by <code>DQT</code> (and
+<code>DHT</code> for non-progressive writes) marker segments, followed by the
+<code>SOF</code> and <code>SOS</code> marker segments. For progressive writes
+using metadata to control progression, the <code>SOS</code> segments are used
+in the order in which their corresponding nodes occur in the
+<code>markerSequence</code> node.
+<p>
+
+The <code>reset</code>, <code>mergeTree</code> and <code>setFromTree</code>
+operations have the following semantics for the JPEG plug-in metadata object:
+
+<p> <code>reset</code> - A call to <code>reset</code> will restore the
+metadata object to the same state it had immediately after creation, whether
+this came about from reading a stream or by obtaining a default object from
+the <code>ImageWriter</code>. This is true regardless of how many times the
+metadata object has been modified since creation.
+
+<p> <code>mergeTree</code> - Native Format
+<br> The <code>mergeTree</code> operation accepts valid trees conforming to
+the DTD below, and merges the nodes using the following ordering rules. In
+all cases, only data present in the new node is changed in a corresponding
+existing node, if any. This means that nodes cannot be removed using
+<code>mergeTree</code>. To remove nodes, use <code>setFromTree</code>. The
+tree must consist of <code>IIOMetadataNode</code>s.
+<ul>
+ <li> <code>app0JFIF</code>
+ <ul>
+ <li> If an <code>app0JFIF</code> node already exists, the contents
+ of the new one modify the existing one.
+ <li> If there is no such node, a new one is created and inserted in
+ the appropriate position.
+ </ul>
+ <li> <code>dqt</code>
+ <ul>
+ <li> If there already exist <code>dqt</code> nodes in the sequence,
+ then each table in the node replaces the first table, in any
+ <code>dqt</code> node, with the same table id.
+ <li> If none of the existing <code>dqt</code> nodes contain a table
+ with the same id, then the table is added to the last existing
+ <code>dqt</code> node.
+ <li> If there are no <code>dqt</code> nodes, then a new one is
+ created and added as follows:
+ <ul>
+ <li> If there are <code>dht</code> nodes, the new
+ <code>dqt</code> node is inserted before the first one.
+ <li> If there are no <code>dht</code> nodes, the new
+ <code>dqt</code> node is inserted before an
+ <code>sof</code> node, if there is one.
+ <li> If there is no <code>sof</code> node, the new
+ <code>dqt</code> node is inserted before the first
+ <code>sos</code> node, if there is one.
+ <li> If there is no <code>sos</code> node, the new
+ <code>dqt</code> node is added to the end of the sequence.
+ </ul>
+ </ul>
+ <li> <code>dht</code>
+ <ul>
+ <li> If there already exist <code>dht</code> nodes in the sequence,
+ then each table in the node replaces the first table, in any
+ <code>dht</code> node, with the same table class and table id.
+ <li> If none of the existing <code>dht</code> nodes contain a table
+ with the same class and id, then the table is added to the last
+ existing <code>dht</code> node.
+ <li> If there are no <code>dht</code> nodes, then a new one is
+ created and added as follows:
+ <ul>
+ <li> If there are <code>dqt</code> nodes, the new
+ <code>dht</code> node is inserted immediately following the
+ last <code>dqt</code> node.
+ <li> If there are no <code>dqt</code> nodes, the new
+ <code>dht</code> node is inserted before an
+ <code>sof</code> node, if there is one.
+ <li> If there is no <code>sof</code> node, the new
+ <code>dht</code> node is inserted before the first
+ <code>sos</code> node, if there is one.
+ <li> If there is no <code>sos</code> node, the new
+ <code>dht</code> node is added to the end of the sequence.
+ </ul>
+ </ul>
+ <li> <code>dri</code>
+ <ul>
+ <li> If there already exists a <code>dri</code> node, the restart
+ interval value is updated.
+ <li> If there is no <code>dri</code> node, then a new one is created
+ and added as follows:
+ <ul>
+ <li> If there is an <code>sof</code> node, the new
+ <code>dri</code> node is inserted before it.
+ <li> If there is no <code>sof</code> node, the new
+ <code>dri</code> node is inserted before the first
+ <code>sos</code> node, if there is one.
+ <li> If there is no <code>sos</code> node, the new
+ <code>dri</code> node is added to the end of the sequence.
+ </ul>
+ </ul>
+ <li> <code>com</code>
+ <br> A new <code>com</code> node is created and inserted as follows:
+ <ul>
+ <li> If there already exist <code>com</code> nodes, the new one is
+ inserted after the last one.
+ <li> If there are no <code>com</code> nodes, the new
+ <code>com</code> node is inserted after the
+ <code>app14Adobe</code> node, if there is one.
+ <li> If there is no <code>app14Adobe</code> node, the new
+ <code>com</code> node is inserted at the beginning of the
+ sequence.
+ </ul>
+ <li> <code>app14Adobe</code>
+ <ul>
+ <li> If there already exists an <code>app14Adobe</code> node, then
+ its attributes are updated from the node.
+ <li> If there is no <code>app14Adobe</code> node, then a new one is
+ created and added as follows:
+ <ul>
+ <li> The new <code>app14Adobe</code> node is inserted after the
+ last <code>unknown</code> node, if there are any.
+ <li> If there are no <code>unknown</code> nodes, the new
+ <code>app14Adobe</code> node is inserted at the beginning
+ of the sequence.
+ </ul>
+ </ul>
+ <li> <code>unknown</code>
+ <br> A new <code>unknown</code> node is created and added to the
+ sequence as follows:
+ <ul>
+ <li> If there already exist <code>unknown</code> marker nodes, the
+ new one is inserted after the last one.
+ <li> If there are no <code>unknown</code> nodes, the new
+ <code>unknown</code> node is inserted before the
+ <code>app14Adobe</code> node, if there is one.
+ <li> If there is no <code>app14Adobe</code> node, the new
+ <code>unknown</code> node is inserted at the beginning of the
+ sequence.
+ </ul>
+ <li> <code>sof</code>
+ <ul>
+ <li> If there already exists an <code>sof</code> node in the
+ sequence, then its values are updated from the node.
+ <li> If there is no <code>sof</code> node, then a new one is created
+ and added as follows:
+ <ul>
+ <li> If there are any <code>sos</code> nodes, the new
+ <code>sof</code> node is inserted before the first one.
+ <li> If there is no <code>sos</code> node, the new
+ <code>sof</code> node is added to the end of the sequence.
+ </ul>
+ </ul>
+ <li> <code>sos</code>
+ <ul>
+ <li> If there already exists a single <code>sos</code> node, then
+ the values are updated from the node.
+ <li> If there are more than one existing <code>sos</code> nodes,
+ then an <code>IIOInvalidTreeException</code> is thrown, as
+ <code>sos</code> nodes cannot be merged into a set of
+ progressive scans.
+ <li> If there are no <code>sos</code> nodes, a new one is created
+ and added to the end of the sequence.
+ </ul>
+</ul>
+
+<p> <code>mergeTree</code> - Standard Format
+<br>
+The <code>mergeTree</code> operation, when given a tree in the standard
+format, will modify the native tree in the following ways:
+<ul>
+ <li> <code>Chroma</code> - The <code>ColorSpaceType</code> subnode of a
+ <code>Chroma</code> node may change the target colorspace of the
+ compressed image. The selection of a new colorspace can cause a number
+ of changes, in keeping with the algorithms described above:
+ <code>app0JFIF</code> and <code>app14Adobe</code> nodes may be added
+ or removed, subsampling may be added or removed, component ids may
+ be changed, and <code>sof</code> and <code>sos</code> nodes will be
+ updated accordingly. If necessary, additional quantization and
+ huffman tables are added. In the case of quantization tables, the
+ default will be scaled to match the quality level of any existing
+ tables. No tables are added to metadata that does not already contain
+ tables. If the existing metadata specifies progressive encoding, then
+ the number of channels must not change. Any <code>Transparency</code>
+ node is also taken into account, as an explicit value of
+ <code>none</code> for the <code>Alpha</code> subnode can cause the
+ removal of an alpha channel, and anything other than <code>none</code>
+ can cause the addition of an alpha channel.
+ <li> <code>Dimension</code> - A <code>PixelAspectRatio</code> specification
+ can cause the contents of an <code>app0JFIF</code> node to change, if
+ there is one present, or the addition of an <code>app0JFIF</code> node
+ containing appropriate values, if there can be one. An appropriate
+ pair of integers is computed from the floating-point ratio for
+ inclusion in the node.
+ <li> <code>Text</code> - Each uncompressed text item is converted to a
+ <code>com</code> node and inserted according to the rules above for
+ merging <code>com</code> nodes.
+</ul>
+
+<p> <code>setFromTree</code> - Native Format
+<br>
+The <code>setFromTree</code> operation, when given a tree in the native
+format described below, will simply replace the existing tree in its entirety
+with the new one. The tree must consist of <code>IIOMetadataNode</code>s.
+
+<p> <code>setFromTree</code> - Standard Format
+<br>
+The <code>setFromTree</code> operation, when given a tree in the standard
+format, performs a <code>reset</code> followed by a merge of the new tree.
+
+<h2>
+<a name=image>Image Metadata DTD</a>
+</h2>
+
+<pre>
+<!DOCTYPE "javax_imageio_jpeg_image_1.0" [
+
+ <!ELEMENT "javax_imageio_jpeg_image_1.0" (JPEGvariety, markerSequence)>
+
+ <!ELEMENT "JPEGvariety" (app0JFIF)>
+ <!-- A node grouping all marker segments specific to the variety of
+ stream being read/written (e.g. JFIF) - may be empty -->
+
+ <!ELEMENT "app0JFIF" (JFXX?, app2ICC?)>
+ <!ATTLIST "app0JFIF" "majorVersion" #CDATA "1">
+ <!-- The major JFIF version number -->
+ <!-- Data type: Integer -->
+ <!-- Min value: 0 (inclusive) -->
+ <!-- Max value: 255 (inclusive) -->
+ <!ATTLIST "app0JFIF" "minorVersion" #CDATA "2">
+ <!-- The minor JFIF version number -->
+ <!-- Data type: Integer -->
+ <!-- Min value: 0 (inclusive) -->
+ <!-- Max value: 255 (inclusive) -->
+ <!ATTLIST "app0JFIF" "resUnits" ("0" | "1" | "2") "0">
+ <!-- The resolution units for Xdensisty and Ydensity (0 = no
+ units, just aspect ratio; 1 = dots/inch; 2 = dots/cm) -->
+ <!ATTLIST "app0JFIF" "Xdensity" #CDATA "1">
+ <!-- The horizontal density or aspect ratio numerator -->
+ <!-- Data type: Integer -->
+ <!-- Min value: 1 (inclusive) -->
+ <!-- Max value: 65535 (inclusive) -->
+ <!ATTLIST "app0JFIF" "Ydensity" #CDATA "1">
+ <!-- The vertical density or aspect ratio denominator -->
+ <!-- Data type: Integer -->
+ <!-- Min value: 1 (inclusive) -->
+ <!-- Max value: 65535 (inclusive) -->
+ <!ATTLIST "app0JFIF" "thumbWidth" #CDATA "0">
+ <!-- The width of the thumbnail, or 0 if there isn't one -->
+ <!-- Data type: Integer -->
+ <!-- Min value: 0 (inclusive) -->
+ <!-- Max value: 255 (inclusive) -->
+ <!ATTLIST "app0JFIF" "thumbHeight" #CDATA "0">
+ <!-- The height of the thumbnail, or 0 if there isn't one -->
+ <!-- Data type: Integer -->
+ <!-- Min value: 0 (inclusive) -->
+ <!-- Max value: 255 (inclusive) -->
+
+ <!ELEMENT "JFXX" (app0JFXX)*>
+ <!-- Min children: 1 -->
+
+ <!ELEMENT "app0JFXX" (JFIFthumbJPEG | JFIFthumbPalette |
+ JFIFthumbRGB)>
+ <!-- A JFIF extension marker segment -->
+ <!ATTLIST "app0JFXX" "extensionCode" ("16" | "17" | "19")
+ #IMPLIED>
+ <!-- The JFXX extension code identifying thumbnail type: (16 =
+ JPEG, 17 = indexed, 19 = RGB -->
+
+ <!ELEMENT "JFIFthumbJPEG" (markerSequence?)>
+ <!-- A JFIF thumbnail in JPEG format (no JFIF segments
+ permitted) -->
+
+ <!ELEMENT "JFIFthumbPalette" EMPTY>
+ <!-- A JFIF thumbnail as an RGB indexed image -->
+ <!ATTLIST "JFIFthumbPalette" "thumbWidth" #CDATA #IMPLIED>
+ <!-- The width of the thumbnail -->
+ <!-- Data type: Integer -->
+ <!-- Min value: 0 (inclusive) -->
+ <!-- Max value: 255 (inclusive) -->
+ <!ATTLIST "JFIFthumbPalette" "thumbHeight" #CDATA #IMPLIED>
+ <!-- The height of the thumbnail -->
+ <!-- Data type: Integer -->
+ <!-- Min value: 0 (inclusive) -->
+ <!-- Max value: 255 (inclusive) -->
+
+ <!ELEMENT "JFIFthumbRGB" EMPTY>
+ <!-- A JFIF thumbnail as an RGB image -->
+ <!ATTLIST "JFIFthumbRGB" "thumbWidth" #CDATA #IMPLIED>
+ <!-- The width of the thumbnail -->
+ <!-- Data type: Integer -->
+ <!-- Min value: 0 (inclusive) -->
+ <!-- Max value: 255 (inclusive) -->
+ <!ATTLIST "JFIFthumbRGB" "thumbHeight" #CDATA #IMPLIED>
+ <!-- The height of the thumbnail -->
+ <!-- Data type: Integer -->
+ <!-- Min value: 0 (inclusive) -->
+ <!-- Max value: 255 (inclusive) -->
+
+ <!ELEMENT "app2ICC" EMPTY>
+ <!-- An ICC profile APP2 marker segment -->
+ <!-- Optional User object: java.awt.color.ICC_Profile -->
+
+ <!ELEMENT "markerSequence" (dqt | dht | dri | com | unknown |
+ app14Adobe | sof | sos)*>
+ <!-- A node grouping all non-jfif marker segments -->
+
+ <!ELEMENT "dqt" (dqtable)*>
+ <!-- A Define Quantization Table(s) marker segment -->
+ <!-- Min children: 1 -->
+ <!-- Max children: 4 -->
+
+ <!ELEMENT "dqtable" EMPTY>
+ <!-- A single quantization table -->
+ <!-- User object: javax.imageio.plugins.jpeg.JPEGQTable -->
+ <!ATTLIST "dqtable" "elementPrecision" #CDATA "0">
+ <!-- The number of bits in each table element (0 = 8, 1 = 16)
+ -->
+ <!-- Data type: Integer -->
+ <!ATTLIST "dqtable" "qtableId" ("0" | "1" | "2" | "3") #REQUIRED>
+
+ <!ELEMENT "dht" (dhtable)*>
+ <!-- A Define Huffman Table(s) marker segment -->
+ <!-- Min children: 1 -->
+ <!-- Max children: 4 -->
+
+ <!ELEMENT "dhtable" EMPTY>
+ <!-- A single Huffman table -->
+ <!-- User object: javax.imageio.plugins.jpeg.JPEGHuffmanTable -->
+ <!ATTLIST "dhtable" "class" ("0" | "1") #REQUIRED>
+ <!-- Indicates whether this is a DC (0) or an AC (1) table -->
+ <!ATTLIST "dhtable" "htableId" ("0" | "1" | "2" | "3") #REQUIRED>
+ <!-- The table id -->
+
+ <!ELEMENT "dri" EMPTY>
+ <!-- A Define Restart Interval marker segment -->
+ <!ATTLIST "dri" "interval" #CDATA #REQUIRED>
+ <!-- The restart interval in MCUs -->
+ <!-- Data type: Integer -->
+ <!-- Min value: 0 (inclusive) -->
+ <!-- Max value: 65535 (inclusive) -->
+
+ <!ELEMENT "com" EMPTY>
+ <!-- A Comment marker segment. The user object contains the actual
+ bytes. -->
+ <!-- User object: array of [B -->
+ <!-- Min length: 1 -->
+ <!-- Max length: 65533 -->
+ <!ATTLIST "com" "comment" #CDATA #IMPLIED>
+ <!-- The comment as a string (used only if user object is null)
+ -->
+ <!-- Data type: String -->
+
+ <!ELEMENT "unknown" EMPTY>
+ <!-- An unrecognized marker segment. The user object contains the
+ data not including length. -->
+ <!-- User object: array of [B -->
+ <!-- Min length: 1 -->
+ <!-- Max length: 65533 -->
+ <!ATTLIST "unknown" "MarkerTag" #CDATA #REQUIRED>
+ <!-- The tag identifying this marker segment -->
+ <!-- Data type: Integer -->
+ <!-- Min value: 0 (inclusive) -->
+ <!-- Max value: 255 (inclusive) -->
+
+ <!ELEMENT "app14Adobe" EMPTY>
+ <!-- An Adobe APP14 marker segment -->
+ <!ATTLIST "app14Adobe" "version" #CDATA "100">
+ <!-- The version of Adobe APP14 marker segment -->
+ <!-- Data type: Integer -->
+ <!-- Min value: 100 (inclusive) -->
+ <!-- Max value: 255 (inclusive) -->
+ <!ATTLIST "app14Adobe" "flags0" #CDATA "0">
+ <!-- The flags0 variable of an APP14 marker segment -->
+ <!-- Data type: Integer -->
+ <!-- Min value: 0 (inclusive) -->
+ <!-- Max value: 65535 (inclusive) -->
+ <!ATTLIST "app14Adobe" "flags1" #CDATA "0">
+ <!-- The flags1 variable of an APP14 marker segment -->
+ <!-- Data type: Integer -->
+ <!-- Min value: 0 (inclusive) -->
+ <!-- Max value: 65535 (inclusive) -->
+ <!ATTLIST "app14Adobe" "transform" ("0" | "1" | "2") #REQUIRED>
+ <!-- The color transform applied to the image (0 = Unknown, 1 =
+ YCbCr, 2 = YCCK) -->
+
+ <!ELEMENT "sof" (componentSpec)*>
+ <!-- A Start Of Frame marker segment -->
+ <!-- Min children: 1 -->
+ <!-- Max children: 4 -->
+ <!ATTLIST "sof" "process" ("0" | "1" | "2") #IMPLIED>
+ <!-- The JPEG process (0 = Baseline sequential, 1 = Extended
+ sequential, 2 = Progressive) -->
+ <!ATTLIST "sof" "samplePrecision" #CDATA "8">
+ <!-- The number of bits per sample -->
+ <!-- Data type: Integer -->
+ <!ATTLIST "sof" "numLines" #CDATA #IMPLIED>
+ <!-- The number of lines in the image -->
+ <!-- Data type: Integer -->
+ <!-- Min value: 0 (inclusive) -->
+ <!-- Max value: 65535 (inclusive) -->
+ <!ATTLIST "sof" "samplesPerLine" #CDATA #IMPLIED>
+ <!-- The number of samples per line -->
+ <!-- Data type: Integer -->
+ <!-- Min value: 0 (inclusive) -->
+ <!-- Max value: 65535 (inclusive) -->
+ <!ATTLIST "sof" "numFrameComponents" ("1" | "2" | "3" | "4")
+ #IMPLIED>
+ <!-- The number of components in the image -->
+
+ <!ELEMENT "componentSpec" EMPTY>
+ <!-- A component specification for a frame -->
+ <!ATTLIST "componentSpec" "componentId" #CDATA #REQUIRED>
+ <!-- The id for this component -->
+ <!-- Data type: Integer -->
+ <!-- Min value: 0 (inclusive) -->
+ <!-- Max value: 255 (inclusive) -->
+ <!ATTLIST "componentSpec" "HsamplingFactor" #CDATA #REQUIRED>
+ <!-- The horizontal sampling factor for this component -->
+ <!-- Data type: Integer -->
+ <!-- Min value: 1 (inclusive) -->
+ <!-- Max value: 255 (inclusive) -->
+ <!ATTLIST "componentSpec" "VsamplingFactor" #CDATA #REQUIRED>
+ <!-- The vertical sampling factor for this component -->
+ <!-- Data type: Integer -->
+ <!-- Min value: 1 (inclusive) -->
+ <!-- Max value: 255 (inclusive) -->
+ <!ATTLIST "componentSpec" "QtableSelector" ("0" | "1" | "2" |
+ "3") #REQUIRED>
+ <!-- The quantization table to use for this component -->
+
+ <!ELEMENT "sos" (scanComponentSpec)*>
+ <!-- A Start Of Scan marker segment -->
+ <!-- Min children: 1 -->
+ <!-- Max children: 4 -->
+ <!ATTLIST "sos" "numScanComponents" ("1" | "2" | "3" | "4")
+ #REQUIRED>
+ <!-- The number of components in the scan -->
+ <!ATTLIST "sos" "startSpectralSelection" #CDATA "0">
+ <!-- The first spectral band included in this scan -->
+ <!-- Data type: Integer -->
+ <!-- Min value: 0 (inclusive) -->
+ <!-- Max value: 63 (inclusive) -->
+ <!ATTLIST "sos" "endSpectralSelection" #CDATA "63">
+ <!-- The last spectral band included in this scan -->
+ <!-- Data type: Integer -->
+ <!-- Min value: 0 (inclusive) -->
+ <!-- Max value: 63 (inclusive) -->
+ <!ATTLIST "sos" "approxHigh" #CDATA "0">
+ <!-- The highest bit position included in this scan -->
+ <!-- Data type: Integer -->
+ <!-- Min value: 0 (inclusive) -->
+ <!-- Max value: 15 (inclusive) -->
+ <!ATTLIST "sos" "approxLow" #CDATA "0">
+ <!-- The lowest bit position included in this scan -->
+ <!-- Data type: Integer -->
+ <!-- Min value: 0 (inclusive) -->
+ <!-- Max value: 15 (inclusive) -->
+
+ <!ELEMENT "scanComponentSpec" EMPTY>
+ <!-- A component specification for a scan -->
+ <!ATTLIST "scanComponentSpec" "componentSelector" #CDATA
+ #REQUIRED>
+ <!-- The id of this component -->
+ <!-- Data type: Integer -->
+ <!-- Min value: 0 (inclusive) -->
+ <!-- Max value: 255 (inclusive) -->
+ <!ATTLIST "scanComponentSpec" "dcHuffTable" ("0" | "1" | "2" |
+ "3") #REQUIRED>
+ <!-- The huffman table to use for encoding DC coefficients -->
+ <!ATTLIST "scanComponentSpec" "acHuffTable" ("0" | "1" | "2" |
+ "3") #REQUIRED>
+ <!-- The huffman table to use for encoding AC coefficients -->
+]>
+</pre>
+
+<h2>
+<a name=stream>Stream Metadata DTD</a>
+</h2>
+
+<pre>
+<!DOCTYPE "javax_imageio_jpeg_stream_1.0" [
+ <!ELEMENT "javax_imageio_jpeg_stream_1.0" (dqt |
+ dht |
+ dri |
+ com |
+ unknown)*>
+
+ <!-- All elements are as defined above for image metadata -->
+]>
+</pre>
+
+</body>
+</html>