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Purpose:
A bugfix and a new document
Description:
ADGuide/Changes.html
New document: "HDF5 Library Changes from Release to Release"
(MUST be updated at EVERY release, including Betas.)
ADGuide/ImageSpec.html
Fixed broken links and title tag.
Platforms tested:
IE 5
732 lines
20 KiB
HTML
Executable File
732 lines
20 KiB
HTML
Executable File
<html>
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<head>
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<title>Image Specification</title>
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</head>
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<body bgcolor="#FFFFFF">
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<hr>
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<center>
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<table border=0 width=98%>
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<tr><td valign=top align=left>
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<a href="../index.html">HDF5 documents and links</a> <br>
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<a href="../H5.intro.html">Introduction to HDF5</a> <br>
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<a href="../RM_H5Front.html">HDF5 Reference Manual</a> <br>
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<!--
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<a href="../Glossary.html">Glossary</a><br>
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-->
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</td>
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<td valign=top align=right>
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<br>
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<a href="../H5.user.html">HDF5 User's Guide</a> <br>
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<a href="../ADGuide.html">HDF5 Application Developer's Guide</a>
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</td></tr>
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</table>
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</center>
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<hr>
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<center>
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<h1>HDF5 Image and Palette Specification</h1>
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<h3><i>(Major revision: designated Version 1.1 of the Image and Palette Specification)</i></h3>
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</center>
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The HDF5 specification defines the standard objects and storage for the
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standard HDF5 objects. (For information about the HDF5 library, model and
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specification, see the HDF documentation.) This document is an additional
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specification do define a standard profile for how to store image data
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in HDF5. Image data in HDF5 is stored as HDF5 datasets with standard attributes
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to define the properties of the image.
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<p>This specification defines:
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<ul>
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<li>
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Standard attributes for an Image dataset</li>
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<li>
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Standard storage and attributes for Palettes</li>
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<li>
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Standard for associating Palettes with Images.</li>
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</ul>
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<h2>
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1. HDF5 Image Specification</h2>
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<h3>
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1.1 Overview</h3>
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Image data is stored as an HDF5 dataset with values of HDF5 class Integer
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or Float. A common example would be a two dimensional dataset, with
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elements of type Integer. However, this specification does not limit
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the dimensions or number type that may be used for an Image.
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<p>The dataset for an image is distinguished from other datasets by giving
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it an attribute "CLASS=IMAGE". In addition, the Image dataset has
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an attribute "PALETTE" that points to one or more palettes.
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<p>A Palette is ha HDF5 dataset. A Pallet dataset has an attribute
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"an" and other attributes indicating the type and size of the palette.
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A Palette is an independent object, which can be shared among several Image
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datasets.
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<h3>
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1.2 Image Attributes</h3>
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<dl>
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<dt>
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Attribute name="<b>CLASS</b>"</dt>
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<dd>
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This attribute is of type H5T_C_S1, with size 6.</dd>
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<dd>
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For all Images, the value of this attribute is "IMAGE".</dd>
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</dl>
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<dd>
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This attribute identifies this data set as intended to be interpreted as
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an image that conforms to the specifications on this page.</dd>
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<dl>
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<dt>
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Attribute name="<b>IMAGE_SUBCLASS</b>"</dt>
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<dd>
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If present, the value of this attribute indicates the type of Palette that
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should be used with the Image. This attribute is of type H5T_C_S1,
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with size according to the string. The values are:</dd>
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<dl>
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<dt>
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"IMAGE_GRAYSCALE"</dt>
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<dd>
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A grayscale image, values 0-255 indicating brightness.</dd>
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<dt>
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"IMAGE_BITMAP"</dt>
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<dd>
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A "bit map" image (???)</dd>
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<dt>
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"IMAGE_TRUECOLOR"</dt>
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<dd>
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A truecolor image</dd>
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<dt>
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"IMAGE_INDEXED"</dt>
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<dd>
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An indexed image</dd>
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</dl>
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</dl>
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<dt>
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Attribute name="<b>IMAGE_WHITE_IS_ZERO</b>"</dt>
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<dl>
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<dd>
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This attribute is of type H5T_NATIVE_UCHAR. 0 = false, 1 = true .
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This is used for images with IMAGE_SUBCLASS="IMAGE_GRAYSCALE" or "IMAGE_BITMAP".</dd>
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</dl>
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<dl>
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<dt>
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Attribute name="<b>IMAGE_MINMAXRANGE</b>"</dt>
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<dd>
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If present, this attribute is an array of two numbers, of the same HDF5
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datatype as the data. The first element is the minimum value of the
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data, and the second is the maximum. This is used for images with
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IMAGE_SUBCLASS="IMAGE_GRAYSCALE", "IMAGE_BITMAP" or "IMAGE_INDEXED".</dd>
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</dl>
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<dt>
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Attribute name="<b>IMAGE_BACKGROUNDINDEX</b>"</dt>
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<dl>
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<dd>
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If set, this attribute indicates the index value that should be interpreted
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as the "background color". This attribute is HDF5 type H5T_NATIVE_UINT.</dd>
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</dl>
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<dt>
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Attribute name="<b>IMAGE_TRANSPARENCY</b>"</dt>
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<dl>
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<dd>
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If set, this attribute indicates the index value that should be interpreted
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as the "transparent color". This attribute is HDF5 type H5T_NATIVE_UINT.
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This attribute may not be used for IMAGE_SUBCLASS="IMAGE_TRUE_COLOR".</dd>
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</dl>
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<dt>
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Attribute name="<b>IMAGE_ASPECTRATIO</b>"</dt>
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<dl>
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<dd>
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If set, this attribute indicates the aspect ratio. This attribute
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is HDF5 type H5T_NATIVE_UINT.</dd>
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</dl>
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<dt>
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Attribute name="<b>IMAGE_COLORMODEL</b>"</dt>
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<dl>
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<dd>
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If set, this attribute indicates the color model of Palette that should
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be used with the Image. This attribute is of type H5T_C_S1, with
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size 4,5, or 6. The value is one of the color models described in
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the Palette specification below. This attribute may be used only
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for IMAGE_SUBCLASS="IMAGE_TRUECOLOR" or "IMAGE_INDEXED".</dd>
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</dl>
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<dt>
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Attribute name="<b>IMAGE_GAMMACORRECTION</b>"</dt>
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<dl>
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<dd>
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If set, this attribute gives the Gamma correction. The type is H5T_NATIVE_FLOAT.
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This attribute may be used only for IMAGE_SUBCLASS="IMAGE_TRUECOLOR" or
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"IMAGE_INDEXED".</dd>
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</dl>
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<dt>
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Attribute name="<b>PALETTE</b>"</dt>
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<dl>
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<dd>
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A dataset within an HDF5 file may optionally specify an array of palettes
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to be viewed with. The dataset will have an attribute field called "<b>PALETTE</b>"
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which contains an array of object reference pointers which refer to palettes
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in the file. The first palette in this array will be the default palette
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that the data may be viewed with.</dd>
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</dl>
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Attribute name="<b>IMAGE_VERSION</b>"
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<dl>
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<dd>
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This attribute is of type H5T_C_S1, with size corresponding to the length
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of the version string. This attribute identifies the version number
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of this specification to which it conforms. The initial version number
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is "1.0".</dd>
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<br>
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<p>
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<br>
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<br>
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<center><table BORDER=2 BGCOLOR="#FFFFFF" >
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<caption>Attributes of an Image Dataset</caption>
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<tr>
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<td><b>Attribute Name</b></td>
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<td></td>
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<td><b>Type</b></td>
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<td><b>Value</b></td>
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</tr>
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<tr>
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<td>CLASS</td>
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<td>R</td>
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<td>String</td>
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<td>"IMAGE"</td>
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</tr>
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<tr>
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<td>PALETTE</td>
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<td>O</td>
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<td>Array of Object References</td>
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<td><references to Palette datasets><sup>1</sup></td>
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</tr>
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<tr>
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<td>IMAGE_SUBCLASS</td>
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<td>O<sup>2</sup></td>
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<td>String</td>
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<td>
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<dt>
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"IMAGE_GRAYSCALE",</dt>
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<dt>
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"IMAGE_BITMAP",</dt>
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<dt>
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"IMAGE_TRUECOLOR",</dt>
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<dt>
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"IMAGE_INDEXED"</dt>
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</td>
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</tr>
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<tr>
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<td>PALETTE</td>
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<td>O</td>
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<td>Array of Object Reference</td>
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<td><references to Palette datasets></td>
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</tr>
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<tr>
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<td>IMAGE_WHITE_IS_ZERO</td>
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<td>O<sup>3,4</sup></td>
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<td>Unsigned Integer</td>
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<td>0 = false, 1 = true</td>
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</tr>
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<tr>
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<td>IMAGE_MINMAXRANGE</td>
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<td>O<sup>3,5</sup></td>
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<td>Unsigned Integer[2]</td>
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<td>The (<minimum>, <maximum>) value of the data.</td>
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</tr>
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<tr>
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<td>IMAGE_BACKGROUNDINDEX</td>
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<td>O<sup>3</sup></td>
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<td>Unsigned Integer</td>
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<td>The index of the background color.</td>
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</tr>
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<tr>
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<td>IMAGE_TRANSPARENCY</td>
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<td>O<sup>3,5</sup></td>
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<td>Unsigned Integer</td>
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<td>The index of the transparent color.</td>
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</tr>
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<tr>
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<td>IMAGE_ASPECTRATIO</td>
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<td>O<sup>3,4</sup></td>
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<td>Unsigned Integer</td>
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<td>The aspect ratio.</td>
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</tr>
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<tr>
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<td>IMAGE_COLORMODEL</td>
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<td>O<sup>3,6</sup></td>
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<td>String</td>
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<td>The color model, as defined below in the Palette specification for
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attribute <b>PAL_COLORMODEL</b>.</td>
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</tr>
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<tr>
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<td>IMAGE_GAMMACORRECTION</td>
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<td>O<sup>3,6</sup></td>
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<td>Float</td>
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<td>The gamma correction.</td>
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</tr>
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<tr>
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<td>IMAGE_VERSION</td>
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<td>R</td>
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<td>String</td>
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<td><specification version number></td>
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</tr>
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</table></center>
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<dl><font size=-1>1. The first element of the array is the default
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Palette.</font>
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<br><font size=-1>2. This attribute is <b>required</b> for images
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that are converted from one of the standard types listed.</font>
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<br><font size=-1>3. This attribute is <b>required</b> if set for images
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converted from the applicable standard type.</font>
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<br><font size=-1>4. This applies to gray scale images: IMAGE_SUBCLASS="IMAGE_GRAYSCALE"
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or "IMAGE_BITMAP".</font>
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<br><font size=-1>5. This applies to gray scale images: IMAGE_SUBCLASS="IMAGE_GRAYSCALE",
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"IMAGE_BITMAP", or "IMAGE_INDEXED".</font>
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<br><font size=-1>5. This applies to gray scale images: IMAGE_SUBCLASS="IMAGE_TRUECOLOR",
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or "IMAGE_INDEXED".</font></dl>
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</dl>
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<h3>
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1.3 Storage Properties for Images</h3>
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Image datasets may be stored with any chunking or compression properties
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supported by HDF5.
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<h2>
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2. HDF5 Palette Specification</h2>
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<h3>
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2.1 Overview</h3>
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A palette is the means by which color is applied to an image and is also
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referred to as a color lookup table. It is a table in which every row contains
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the numerical representation of a particular color. In the example of an
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8-bit standard RGB color model palette, this numerical representation of
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a color is presented as a triplet specifying the intensity of red, green,
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and blue components that make up each color.
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<center>
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<p><img SRC="Palettes.fm.anc.gif" ></center>
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<p>In this example, the color component numeric type is an 8-bit unsigned
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integer. While this is most common and recommended for general use, other
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component color numeric datatypes, such as a 16-bit unsigned integer ,
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may be used. This type is specified as the type attribute of the palette
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dataset. (see H5Tget_type(), H5Tset_type())
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<p>The minimum and maximum values of the component color numeric are specified
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as attribute of the palette dataset. See below (attribute PAL_MINMAXNUMERIC).
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If these attributes do not exist, it is assumed that the range of values
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will fill the space of the color numeric type. i.e. with an 8-bit unsigned
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integer, the valid range would be 0 to 255 for each color component.
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<p>The HDF5 palette specification additionally allows for color models
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beyond RGB. YUV, HSV, CMY, CMYK, YCbCr color models are supported, and
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may be specified as a color model attribute of the palette dataset. <i>(see
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"Palette Attributes" for details)</i>.
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<p>In HDF 4 and earlier, palettes were limited to 256 colors. The HDF5
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palette specification allows for palettes of varying length. The length
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is specified as the number of rows of the palette dataset.
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<p>In a standard palette, the color entries are indexed directly. HDF5
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supports the notion of a range index table. Such a table defines an ascending
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ordered of ranges that map dataset values to the palette. If a range index
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table exists for the palette, the PAL_TYPE attribute will be set to "RANGEINDEX",
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and the PAL_RANGEINDEX attribute will contain an object reference to a
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range index table array. If not, the PAL_TYPE attribute either does not
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exist, or will be set to "STANDARD".
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<p>The range index table array consists of a one dimensional array with
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the same length as the palette dataset - 1. Ideally, the range index would
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be of the same type as the dataset it refers to, however this is not a
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requirement.
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<p><b>Example 2: A range index array of type floating point</b>
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<center>
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<p><img SRC="PaletteExample1.gif" ></center>
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<p>The range index array attribute defines the "<i>to</i>" of the range.
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Notice that the range index array attribute is one less entry in size than
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the palette. The first entry of 0.1259, specifies that all values below
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and up to 0.1259 inclusive, will map to the first palette entry. The second
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entry signifies that all values greater than 0.1259 up to 0.3278 inclusive,
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will map to the second palette entry, etc. All value greater than the last
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range index array attribute (100000) map to the last entry in the palette.
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<h3>
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2.2. Palette Attributes</h3>
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A palette exists in an HDF file as an independent data set with accompanying
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attributes.
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<p>These attributes are defined as follows:
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<dl>
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<dt>
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Attribute name="<b>CLASS</b>"</dt>
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<dd>
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This attribute is of type H5T_C_S1, with size 8.</dd>
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<dd>
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For all palettes, the value of this attribute is "PALETTE". This attribute
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identifies this palette data set as a palette that conforms to the specifications
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on this page.</dd>
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<dt>
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Attribute name="<b>PAL_COLORMODEL</b>"</dt>
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<dd>
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This attribute is of type H5T_C_S1, with size 4, 5, or 6.</dd>
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<dd>
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Possible values for this are "RGB", "YUV", "CMY", "CMYK", "YCbCr", "HSV".</dd>
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<dd>
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This defines the color model that the entries in the palette data set represent.</dd>
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<dl>
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<dt>
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"RGB"</dt>
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<dd>
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Each color index contains a triplet where the the first value defines the
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red component, second defines the green component, and the third the blue
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component.</dd>
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<dt>
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"CMY"</dt>
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<dd>
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Each color index contains a triplet where the the first value defines the
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cyan component, second defines the magenta component, and the third the
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yellow component.</dd>
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<dt>
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"CMYK"</dt>
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<dd>
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Each color index contains a quadruplet where the the first value defines
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the cyan component, second defines the magenta component, the third the
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yellow component, and the forth the black component.</dd>
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<dt>
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"YCbCr"</dt>
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<dd>
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Class Y encoding model. Each color index contains a triplet where the the
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first value defines the luminance, second defines the Cb Chromonance, and
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the third the Cr Chromonance.</dd>
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<dt>
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"YUV"</dt>
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<dd>
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Composite encoding color model. Each color index contains a triplet where
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the the first value defines the luminance component, second defines the
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chromonance component, and the third the value component.</dd>
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<dt>
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"HSV"</dt>
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<dd>
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Each color index contains a triplet where the the first value defines the
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hue component, second defines the saturation component, and the third the
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value component. The hue component defines the hue spectrum with a low
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value representing magenta/red progressing to a high value which would
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represent blue/magenta, passing through yellow, green, cyan. A low value
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for the saturation component means less color saturation than a high value.
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A low value for <i>value</i> will be darker than a high value.</dd>
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</dl>
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<dt>
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Attribute name="<b>PAL_TYPE</b>"</dt>
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<dd>
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This attribute is of type H5T_C_S1, with size 10 or 11.</dd>
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<br>The current supported values for this attribute are : "STANDARD8" or
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"RANGEINDEX"
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<p>A PAL_TYPE of "STANDARD8" defines a palette dataset such that the first
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entry defines index 0, the second entry defines index 1, etc. up until
|
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the length of the palette - 1. This assumes an image dataset with direct
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indexes into the palette.
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<p>If the PAL_TYPE is set to "RANGEINDEX", there will be an additional
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attribute with a name of "<b>PAL_RANGEINDEX</b>", (See example 2
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for more details)
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<dt>
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Attribute name="<b>PAL_RANGEINDEX</b>"</dt>
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<dd>
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The <b>PAL_RANGEINDEX</b> attribute contains an HDF object reference pointer
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which specifies a range index array in the file to be used for color lookups
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for the palette. (Only for PAL_TYPE="RANGEINDEX"</dd>
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<dt>
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Attribute name="<b>PAL_MINMAXNUMERIC</b>"</dt>
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<dl>
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<dt>
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If present, this attribute is an array of two numbers, of the same HDF5
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datatype as the palette elements or color numerics.</dt>
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|
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<br>They specify the minimum and maximum values of the color numeric components.
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For example, if the palette was an RGB of type Float, the color numeric
|
|
range for Red, Green, and Blue could be set to be between 0.0 and 1.0.
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The intensity of the color guns would then be scaled accordingly to be
|
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between this minimum and maximum attribute.</dl>
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Attribute name="<b>PAL_VERSION</b>"
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<dl>This attribute is of type H5T_C_S1, with size corresponding to the
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length of the version string. This attribute identifies the version
|
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number of this specification to which it conforms. The initial version
|
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number is "1.0".</dl>
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<center><table BORDER=2 BGCOLOR="#FFFFFF" >
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<caption><b>Attributes of a Palette Dataset</b></caption>
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<tr>
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<td><b>Attribute Name</b></td>
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|
<td></td>
|
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<td><b>Type</b></td>
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<td><b>Value</b></td>
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</tr>
|
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|
<tr>
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<td>CLASS</td>
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<td>R</td>
|
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|
<td>String</td>
|
|
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<td>"PALETTE"</td>
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</tr>
|
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<tr>
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<td>PAL_COLORMODEL</td>
|
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|
|
<td>R</td>
|
|
|
|
<td>String</td>
|
|
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|
<td>Color Model: "RGB", YUV", "CMY", "CMYK", "YCbCr", or "HSV"</td>
|
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</tr>
|
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<tr>
|
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<td>PAL_TYPE</td>
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|
<td>R</td>
|
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<td>String</td>
|
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<td>"STANDARD8" or "RANGEINDEX"</td>
|
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</tr>
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<tr>
|
|
<td>RANGE_INDEX</td>
|
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|
|
<td>R<sup>1</sup></td>
|
|
|
|
<td>Object Reference </td>
|
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|
|
<td><Object Reference to Dataset of range index values></td>
|
|
</tr>
|
|
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|
<tr>
|
|
<td>PAL_MINMAXNUMERIC</td>
|
|
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|
<td>O</td>
|
|
|
|
<td>Array[2] of <same datatype as palette></td>
|
|
|
|
<td>The first value is the <Minimum value for color values>, the second
|
|
value is <Maximum value for color values><sup>2</sup></td>
|
|
</tr>
|
|
|
|
<tr>
|
|
<td>PAL_VERSION</td>
|
|
|
|
<td>R</td>
|
|
|
|
<td>String</td>
|
|
|
|
<td><specification version number></td>
|
|
</tr>
|
|
</table></center>
|
|
|
|
<dl><font size=-1>1. The RANGE_INDEX attribute is required if the
|
|
PAL_TYPE is "RANGEINDEX". Otherwise, the RANGE_INDEX attribute should
|
|
be omitted.</font>
|
|
<br><font size=-1>2. The minimum and maximum are optional.
|
|
If not set, the range is assumed to the maximum range of the number type.
|
|
If one of these attributes is set, then both should be set. The value
|
|
of the minumum must be less than or equal to the value of the maximum.</font></dl>
|
|
</dl>
|
|
|
|
<h3>
|
|
2.3. Storage Layout for Palettes</h3>
|
|
The values of the Palette are stored as a dataset. The datatype can
|
|
be any HDF 5 atomic numeric type. The dataset will have dimensions
|
|
(<tt>nentries</tt> by <tt>ncomponents</tt>), where '<tt>nentries</tt>'
|
|
is the number of colors (usually 256) and '<tt>ncomponents'</tt> is the
|
|
number of values per color (3 for <b>RGB</b>, 4 for <b>CMYK</b>, etc.)
|
|
<br>
|
|
<h2>
|
|
3. Consistency and Correlation of Image and Palette Attributes</h2>
|
|
The objects in this specification are an extension to the base HDF5 specification
|
|
and library. They are accessible with the standard HDF5 library,
|
|
but the semantics of the objects are not enforced by the base library.
|
|
For example, it is perfectly possible to add an attribute called <b>IMAGE</b>
|
|
to <i>any</i> dataset, or to include an object reference to <i>any</i>
|
|
HDF5 dataset as a "palette" in a <b>PALETTE</b> attribute. this would
|
|
be a perfectly valid HDF5 file, but not conformant to this specification.
|
|
The rules defined in this specification must be implemented with appropriate
|
|
software, and applications must use conforming software to assure correctness.
|
|
<p>The Image and Palette specifications include several mutually redundant
|
|
standard attributes, such as the <b>IMAGE_COLORMODEL</b> and the <b>PAL_COLORMODEL</b>.
|
|
These attributes are informative not normative, in that it is acceptable
|
|
to attach a Palette to an Image dataset even if their attributes do not
|
|
match. Software is not required to enforce consistency, and files
|
|
may contain mismatched associations of Images and Palettes. In all
|
|
cases, it is up to applications to determine what kinds of images and color
|
|
models can be supported.
|
|
<p>For example, an Image that was created from a file with an "RGB" may
|
|
have a "YUV" Palette in its <b>PALETTE</b> attribute array. This
|
|
would be a legal HDF5 file and also a conforms to this specification, although
|
|
it may or may not be correct or useable for a given application.
|
|
<p>
|
|
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<hr>
|
|
<center>
|
|
<table border=0 width=98%>
|
|
<tr><td valign=top align=left>
|
|
<a href="../index.html">HDF5 documents and links</a> <br>
|
|
<a href="../H5.intro.html">Introduction to HDF5</a> <br>
|
|
<a href="../RM_H5Front.html">HDF5 Reference Manual</a> <br>
|
|
<!--
|
|
<a href="../Glossary.html">Glossary</a><br>
|
|
-->
|
|
</td>
|
|
<td valign=top align=right>
|
|
<br>
|
|
<a href="../H5.user.html">HDF5 User's Guide</a> <br>
|
|
<a href="../ADGuide.html">HDF5 Application Developer's Guide</a>
|
|
</td></tr>
|
|
</table>
|
|
</center>
|
|
|
|
|
|
|
|
<hr>
|
|
<address>
|
|
<a href="mailto:hdfhelp@ncsa.uiuc.edu">HDF Help Desk</a>
|
|
</address>
|
|
|
|
<!-- Created: Spring 1999 -->
|
|
<!-- hhmts start -->
|
|
Last modified: 2 June 2000
|
|
<!-- hhmts end -->
|
|
|
|
<br>
|
|
Describes HDF5 Release 1.4 Beta, December 2000
|
|
|
|
|
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</body>
|
|
</html>
|