e6c1d392e3
Palettes.html Various copy-edits and cleaned up HTML. Caching.html Edited section headers and added an <h1> header. Errors.html Added section title "Error Handling Operations."
289 lines
12 KiB
HTML
Executable File
289 lines
12 KiB
HTML
Executable File
<html>
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<head>
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<title>Palettes</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="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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<a href="index.html">Other HDF5 documents and links</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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And in this document, the
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<a href="H5.user.html"><strong>HDF5 User's Guide:</strong></a>
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<br>
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<a href="Files.html">Files</a>
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<a href="Datasets.html">Datasets</a>
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<a href="Datatypes.html">Data Types</a>
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<a href="Dataspaces.html">Dataspaces</a>
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<a href="Groups.html">Groups</a>
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<br>
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<a href="References.html">References</a>
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<a href="Attributes.html">Attributes</a>
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<a href="Properties.html">Property Lists</a>
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<a href="Errors.html">Error Handling</a>
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<br>
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<a href="Filters.html">Filters</a>
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Palettes
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<a href="Caching.html">Caching</a>
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<a href="Chunking.html">Chunking</a>
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<a href="MountingFiles.html">Mounting Files</a>
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<br>
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<a href="Debugging.html">Debugging</a>
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<a href="Environment.html">Environment</a>
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<a href="ddl.html">DDL</a>
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<a href="Ragged.html">Ragged Arrays</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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<H1>HDF5 Palette Specification </H1>
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<P>This section is a work in progress page. Please send comments to <A
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href="mailto:davet@ncsa.uiuc.edu">davet@ncsa.uiuc.edu</A>. Anything and
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everything on this page may be changed.
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<P><B>Questions regarding this specification:</B>
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<UL>
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<LI>Currently, the range index is referred to as an attribute of the palette.
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I'm wondering if it makes more sense for this to be an attribute of the
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dataset... If a palette is to be shared by multiple data sets and each dataset
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has it's own range index mapping, then maybe one would want the index range to
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be an attribute of the palette.
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<LI>Should the range index be separate from the palette, or it be incorporated
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into a 4 column array?
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<LI>Is this method of specifying attributes satisfactory (string name
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identifier with corresponding value), or should they be specified as a struct
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that is read in and written out? The number of attributes is currently at 5.
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</LI></UL>
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<HR>
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<B>Changes made since last revision</B>
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<UL>
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<LI>What was previously called the FLOATRANGE index array has been changed to
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the RANGEINDEX array, and can be of any type, <I>preferably</I> matching that
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of the data set type.
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<LI>A range value min/max attribute for the color numeric may be specified.
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i.e. the red component value of an RGB will be between 0 and 1.
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<LI>A dataset may specify an array of palettes that it may be used with now.
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previously it was just one.
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<LI>CMYK and YCbCr color models have been added. </LI></UL>
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<HR>
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<HR>
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<HR>
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<H2>HDF 5.0 Palette Overview: </H2>
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<P>HDF 5.0 adds the following new features to what existed in earlier HDF
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versions:
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<P>
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<UL>
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<LI>palettes of varying length.
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<LI>definable arbitrary index range
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<LI>definable color model type (RGB, YUV, HSV, CMY, etc.)
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<LI>definable color numeric type </LI></UL>
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<HR>
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<P>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 8-bit
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standard RGB color model palette, this numerical representation of a color is
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presented as a triplet specifying the intensity of red, green, and blue
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components that make up each color.
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<P>
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<CENTER><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 data types, such as a 16-bit unsigned integer , may be
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used. This type is specified as the type attribute of the palette dataset. (see
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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 (attributes PAL_MINNUMERIC,
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PAL_MAXNUMERIC). If these attributes do not exist, it is assumed that the range
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of values will fill the space of the color numeric type. i.e. with an 8-bit
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unsigned integer, the valid range would be 0 to 255 for each color component.
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<P>The HDF 5.0 palette specification additionally allows for color models beyond
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RGB. YUV, HSV, CMY, CMYK, YCbCr color models are supported, and may be specified
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as a color model attribute of the palette dataset. <I>(see "Palette Attributes"
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for details)</I>.
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<P>In HDF 4 and earlier, palettes were limited to 256 colors. The HDF 5.0
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palette specification allows for palettes of varying length. The length is
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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. HDF 5.0
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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 table
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exists for the palette, the PAL_TYPE attribute will be set to "RANGEINDEX", and
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the PAL_RANGEINDEX attribute will contain an object reference to a range index
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table array. If not, the PAL_TYPE attribute either does not exist, or will be
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set to "STANDARD".
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<P>The range index table array consists of a one dimensional array with the same
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length as the palette dataset - 1. Ideally, the range index would be of the same
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type as the dataset it refers to, however this is not a requirement.
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<P><B>Example 2: A range index array of type floating point</B>
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<P>
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<CENTER><IMG src="PaletteExample1.gif"> </CENTER>
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<P>The range index array attribute defines the "<I>to</I>" of the range. Notice
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that the range index array attribute is one less entry in size than the palette.
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The first entry of 0.1259, specifies that all values below and up to 0.1259
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inclusive, will map to the first palette entry. The second entry signifies that
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all values greater than 0.1259 up to 0.3278 inclusive, will map to the second
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palette entry, etc. All value greater than the last range index array attribute
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(100000) map to the last entry in the palette.
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<P>
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<HR>
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<H2>Palette Attributes </H2>
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<P>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>Attribute name="<B>CLASS</B>"
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<DD>This attribute is of type H5T_STR_NULLTERM.
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<DD>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
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specifications on this page.
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<P></P>
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<DT>Attribute name="<B>PAL_COLORMODEL</B>"
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<DD>This attribute is of type H5T_STR_NULLTERM.
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<DD>Possible values for this are "RGB", "YUV", "CMY", "HSV".
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<DD>This defines the color model that the entries in the palette data set
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represent.
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<DL>
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<DT>"RGB"
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<DD>Each color index contains a triplet where the the first value defines
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the red component, second defines the green component, and the third the
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blue component.
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<P></P>
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<DT>"CMY"
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<DD>Each color index contains a triplet where the the first value defines
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the cyan component, second defines the magenta component, and the third the
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yellow component.
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<P></P>
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<DT>"CMYK"
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<DD>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.
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<P></P>
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<DT>"YCbCr"
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<DD>Class Y encoding model. Each color index contains a triplet where the
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the first value defines the luminance, second defines the Cb Chromonance,
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and the third the Cr Chromonance.
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<P></P>
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<DT>"YUV"
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<DD>Composite encoding color model. Each color index contains a triplet
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where the the first value defines the luminance component, second defines
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the chromonance component, and the third the value component.
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<P></P>
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<DT>"HSV"
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<DD>Each color index contains a triplet where the the first value defines
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the hue component, second defines the saturation component, and the third
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the 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 for
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the saturation component means less color saturation than a high value. A
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low value for <I>value</I> will be darker than a high value. </DD></DL>
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<P></P>
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<DT>Attribute name="<B>PAL_TYPE</B>"
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<DD>This attribute is of type H5T_STR_NULLTERM <BR>The current supported
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values for this attribute are : "STANDARD8" or "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 the
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length of the palette - 1. This assumes an image dataset with direct indexes
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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>", The <B>PAL_RANGEINDEX</B>
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attribute contains an HDF object reference pointer which specifies a range
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index array in the file to be used for color lookups for the palette. (See
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example 2 for more details)
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<P></P>
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<DT>Attribute name="<B>PAL_MINNUMERIC</B>"
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<DT>Attribute name="<B>PAL_MAXNUMERIC</B>"
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<DD>These two attributes are of the same type as the palette elements or color
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numerics. <BR>They specify the minimum and maximum values of the color numeric
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components. For example, if the palette was an RGB of type Float, the color
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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 between
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this minimum and maximum attribute. </DD></DL>
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<P>
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<HR>
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<HR>
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<H2>Specifying a Palette for a Dataset </H2>
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A dataset within an HDF5 file may
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specify an array of palettes to be viewed with. The dataset will have an
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attribute field called "<B>PALETTE</B>" which contains an array of object
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reference pointers which refer to palettes in the file. The first palette in
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this array will be the default palette that the data may be viewed with.
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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="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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<a href="index.html">Other HDF5 documents and links</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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And in this document, the
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<a href="H5.user.html"><strong>HDF5 User's Guide:</strong></a>
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<br>
|
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<a href="Files.html">Files</a>
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<a href="Datasets.html">Datasets</a>
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<a href="Datatypes.html">Data Types</a>
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<a href="Dataspaces.html">Dataspaces</a>
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<a href="Groups.html">Groups</a>
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<br>
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<a href="References.html">References</a>
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<a href="Attributes.html">Attributes</a>
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<a href="Properties.html">Property Lists</a>
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<a href="Errors.html">Error Handling</a>
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<br>
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<a href="Filters.html">Filters</a>
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Palettes
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<a href="Caching.html">Caching</a>
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<a href="Chunking.html">Chunking</a>
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<a href="MountingFiles.html">Mounting Files</a>
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<br>
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<a href="Debugging.html">Debugging</a>
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<a href="Environment.html">Environment</a>
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<a href="ddl.html">DDL</a>
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<a href="Ragged.html">Ragged Arrays</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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<address>
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<a href="mailto:hdfhelp@ncsa.uiuc.edu">HDF Help Desk</a>
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</address>
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<!-- Created: Spring 1999 -->
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<!-- hhmts start -->
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Last modified: 23 July 1999
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<!-- hhmts end -->
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</body>
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</html>
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