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If you do not have * - * access to either file, you may request a copy from hdfhelp@ncsa.uiuc.edu. * - * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * - --> - -<link href="../ed_styles/GenElect.css" rel="stylesheet" type="text/css"> -<!-- #EndLibraryItem --></head> - -<body text="#000000" bgcolor="#FFFFFF" link="#0000EE" vlink="#551A8B" alink="#FF0000"> - - -<!-- #BeginLibraryItem "/ed_libs/NavBar_ADevG.lbi" --><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="Glossary.html">Glossary</a><br> - --> -</td> -<td valign=top align=right> - <a href="http://hdf.ncsa.uiuc.edu/HDF5/doc/UG/index.html">HDF5 User's Guide</a> <br> - <a href="../RM_H5Front.html">HDF5 Reference Manual</a> <br> - <a href="../ADGuide.html">HDF5 Application Developer's Guide</a> <br> -</td></tr> -</table> -</center> -<hr> -<!-- #EndLibraryItem --><center> -<h1> -HDF5 Image and Palette Specification</h1></center> - -<center> -<h3> -<i>Version 1.2</i></h3></center> -The HDF5 specification defines the standard objects and storage for the -standard HDF5 objects. (For information about the HDF5 library, model and -specification, see the HDF documentation.) This document is an additional -specification do define a standard profile for how to store image data -in HDF5. Image data in HDF5 is stored as HDF5 datasets with standard attributes -to define the properties of the image. -<p>This specification is primarily concerned with two dimensional raster -data similar to HDF4 Raster Images. Specifications for storing other -types of imagery will be covered in other documents. -<p>This specification defines: -<ul> -<li> -Standard storage and attributes for an Image dataset (<a href="#Sect1">Section -1</a>)</li> - -<li> -Standard storage and attributes for Palettes (<a href="#sect2">Section -2</a>)</li> - -<li> -Standard for associating Palettes with Images. (<a href="#Sect3">Section -3</a>)</li> -</ul> - -<h2> -<a NAME="Sect1"></a>1. HDF5 Image Specification</h2> - -<h3> -1.1 Overview</h3> -Image data is stored as an HDF5 dataset with values of HDF5 class Integer -or Float. A common example would be a two dimensional dataset, with -elements of class Integer, e.g., a two dimensional array of unsigned 8 -bit integers. However, this specification does not limit the dimensions -or number type that may be used for an Image. -<p>The dataset for an image is distinguished from other datasets by giving -it an attribute "CLASS=IMAGE". In addition, the Image dataset may -have an optional attribute "PALETTE" that is an array of object references -for zero or more palettes. The Image dataset may have additional attributes -to describe the image data, as defined in <a href="#Sect1.2">Section 1.2</a>. -<p>A Palette is an HDF5 dataset which contains color map information. -A Pallet dataset has an attribute "CLASS=PALETTE" and other attributes -indicating the type and size of the palette, as defined in <a href="#sect2">Section -2.1</a>. A Palette is an independent object, which can be shared -among several Image datasets. -<h3> -<a NAME="Sect1.2"></a>1.2 Image Attributes</h3> -The attributes for the Image are scalars unless otherwise noted. -The length of String valued attributes should be at least the number of -characters. Optionally, String valued attributes may be stored in a String -longer than the minimum, in which case it must be zero terminated or null -padded. "Required" attributes must always be used. "Optional" attributes -must be used when required. -<br> -<h4> -Attributes</h4> - -<dl> -<dt> -Attribute name="<b>CLASS</b>" (Required)</dt> - -<dd> -This attribute is type H5T_C_S1, with size 5.</dd> - -<dd> -For all Images, the value of this attribute is "IMAGE".</dd> - -<dd> -</dd> - -<dd> -This attribute identifies this data set as intended to be interpreted as -an image that conforms to the specifications on this page.</dd> -</dl> - -<dt> -Attribute name="<b>PALETTE</b>"</dt> - -<dl> -<dd> -A Image dataset within an HDF5 file may optionally specify an array of -palettes to be viewed with. The dataset will have an attribute field called -"<b>PALETTE</b>" which contains a one-dimensional array of object reference -pointers (HDF5 datatype H5T_STD_REF_OBJ) which refer to palettes in the -file. The palette datasets must conform to the Palette specification in -<a href="#sect2">section -2 below</a>. The first palette in this array will be the default palette -that the data may be viewed with.</dd> -</dl> - -<dl> -<dt> -</dt> - -<dt> -Attribute name="<b>IMAGE_SUBCLASS</b>"</dt> - -<dd> -If present, the value of this attribute indicates the type of Palette that -should be used with the Image. This attribute is a scalar of type -H5T_C_S1, with size according to the string plus one. The values -are:</dd> - -<dl> -<dt> -"IMAGE_GRAYSCALE" (length 15)</dt> - -<dd> -A grayscale image</dd> - -<dt> -"IMAGE_BITMAP" (length 12)</dt> - -<dd> -A bit map image</dd> - -<dt> -"IMAGE_TRUECOLOR" (length 15)</dt> - -<dd> -A truecolor image</dd> - -<dt> -"IMAGE_INDEXED" (length 13)</dt> - -<dd> -An indexed image</dd> - -<dd> -</dd> -</dl> - -<dt> -Attribute name="<b>INTERLACE_MODE</b>"</dt> - -<dd> -For images with more than one component for each pixel, this optional attribute -specifies the layout of the data. The values are type H5T_C_S1 of length -15. See <a href="#Section1.3">section 1.3</a> for information about the -storage layout for data.</dd> - -<dd> -"INTERLACE_PIXEL" (default): the component value for a pixel are contiguous.</dd> - -<dd> -"INTERLACE_PLANE": each component is stored as a plane.</dd> - -<dt> -</dt> - -<dt> -Attribute name="<b>DISPLAY_ORIGIN</b>"</dt> - -<dd> -This optional attribute indicates the intended orientation of the data -on a two-dimensional raster display. The value indicates which corner -the pixel at (0, 0) should be viewed. The values are type H5T_C_S1 -of length 2. If DISPLAY_ORIGIN is not set, the orientation is undefined.</dd> - -<dd> -"UL": (0,0) is at the upper left.</dd> - -<dd> -"LL": (0,0) is at the lower left.</dd> - -<dd> -"UR": (0,0) is at the upper right.</dd> - -<dd> -"LR": (0,0) is at the lower right.</dd> -</dl> - -<dt> -Attribute name="<b>IMAGE_WHITE_IS_ZERO</b>"</dt> - -<dl> -<dd> -This attribute is of type H5T_NATIVE_UCHAR. 0 = false, 1 = true . -This is used for images with IMAGE_SUBCLASS="IMAGE_GRAYSCALE" or "IMAGE_BITMAP".</dd> -</dl> - -<dl> -<dt> -Attribute name="<b>IMAGE_MINMAXRANGE</b>"</dt> - -<dd> -If present, this attribute is an array of two numbers, of the same HDF5 -datatype as the data. The first element is the minimum value of the -data, and the second is the maximum. This is used for images with -IMAGE_SUBCLASS="IMAGE_GRAYSCALE", "IMAGE_BITMAP" or "IMAGE_INDEXED".</dd> -</dl> - -<dt> -Attribute name="<b>IMAGE_BACKGROUNDINDEX</b>"</dt> - -<dl> -<dd> -If set, this attribute indicates the index value that should be interpreted -as the "background color". This attribute is HDF5 type H5T_NATIVE_UINT.</dd> -</dl> - -<dt> -Attribute name="<b>IMAGE_TRANSPARENCY</b>"</dt> - -<dl> -<dd> -If set, this attribute indicates the index value that should be interpreted -as the "transparent color". This attribute is HDF5 type H5T_NATIVE_UINT. -This attribute may not be used for IMAGE_SUBCLASS="IMAGE_TRUE_COLOR".</dd> -</dl> - -<dt> -Attribute name="<b>IMAGE_ASPECTRATIO</b>"</dt> - -<dl> -<dd> -If set, this attribute indicates the aspect ratio.</dd> -</dl> - -<dt> -Attribute name="<b>IMAGE_COLORMODEL</b>"</dt> - -<dl> -<dd> -If set, this attribute indicates the color model of Palette that should -be used with the Image. This attribute is of type H5T_C_S1, with -size 3, 4, or 5. The value is one of the color models described in -the Palette specification in <a href="#sect2.2">section 2.2 below</a>. -This attribute may be used only for IMAGE_SUBCLASS="IMAGE_TRUECOLOR" or -"IMAGE_INDEXED".</dd> -</dl> - -<dt> -Attribute name="<b>IMAGE_GAMMACORRECTION</b>"</dt> - -<dl> -<dd> -If set, this attribute gives the Gamma correction. The attribute -is type H5T_NATIVE_FLOAT. This attribute may be used only for IMAGE_SUBCLASS="IMAGE_TRUECOLOR" -or "IMAGE_INDEXED".</dd> -</dl> -Attribute name="<b>IMAGE_VERSION</b>" (Required) -<dl> -<dd> -This attribute is of type H5T_C_S1, with size corresponding to the length -of the version string. This attribute identifies the version number -of this specification to which it conforms. The current version number -is "1.2".</dd> - -<br> -<p> -<br> -<br> -<center><table BORDER=2 BGCOLOR="#FFFFFF" > -<caption><b>Table 1. Attributes of an Image Dataset</b></caption> - -<tr> -<td><b>Attribute Name</b></td> - -<td><b>(R = Required</b> -<br><b>O= Optional)</b></td> - -<td><b>Type</b></td> - -<td><b>String Size</b></td> - -<td><b>Value</b></td> -</tr> - -<tr> -<td>CLASS</td> - -<td>R</td> - -<td>String</td> - -<td>5</td> - -<td>"IMAGE"</td> -</tr> - -<tr> -<td>PALETTE</td> - -<td>O</td> - -<td>Array Object References</td> - -<td></td> - -<td><references to Palette datasets><sup>1</sup></td> -</tr> - -<tr> -<td>IMAGE_SUBCLASS</td> - -<td>O<sup>2</sup></td> - -<td>String</td> - -<td>15, -<br>12, -<br>15, -<br>13</td> - -<td> -<dt> -"IMAGE_GRAYSCALE",</dt> - -<dt> -"IMAGE_BITMAP",</dt> - -<dt> -"IMAGE_TRUECOLOR",</dt> - -<dt> -"IMAGE_INDEXED"</dt> -</td> -</tr> - -<tr> -<td>INTERLACE_MODE</td> - -<td>O<sup>3,6</sup></td> - -<td>String</td> - -<td>15</td> - -<td>The layout of components if more than one component per pixel.</td> -</tr> - -<tr> -<td>DISPLAY_ORIGIN</td> - -<td>O</td> - -<td>String</td> - -<td>2</td> - -<td>If set, indicates the intended location of the pixel (0,0).</td> -</tr> - -<tr> -<td>IMAGE_WHITE_IS_ZERO</td> - -<td>O<sup>3,4</sup></td> - -<td>Unsigned Integer</td> - -<td></td> - -<td>0 = false, 1 = true</td> -</tr> - -<tr> -<td>IMAGE_MINMAXRANGE</td> - -<td>O<sup>3,5</sup></td> - -<td>Array [2] <same datatype as data values></td> - -<td></td> - -<td>The (<minimum>, <maximum>) value of the data.</td> -</tr> - -<tr> -<td>IMAGE_BACKGROUNDINDEX</td> - -<td>O<sup>3</sup></td> - -<td>Unsigned Integer</td> - -<td></td> - -<td>The index of the background color.</td> -</tr> - -<tr> -<td>IMAGE_TRANSPARENCY</td> - -<td>O<sup>3,5</sup></td> - -<td>Unsigned Integer</td> - -<td></td> - -<td>The index of the transparent color.</td> -</tr> - -<tr> -<td>IMAGE_ASPECTRATIO</td> - -<td>O<sup>3,4</sup></td> - -<td>Unsigned Integer</td> - -<td></td> - -<td>The aspect ratio.</td> -</tr> - -<tr> -<td>IMAGE_COLORMODEL</td> - -<td>O<sup>3,6</sup></td> - -<td>String</td> - -<td>3, 4, or 5</td> - -<td>The color model, as defined below in the Palette specification for -attribute <b>PAL_COLORMODEL</b>.</td> -</tr> - -<tr> -<td>IMAGE_GAMMACORRECTION</td> - -<td>O<sup>3,6</sup></td> - -<td>Float</td> - -<td></td> - -<td>The gamma correction.</td> -</tr> - -<tr> -<td>IMAGE_VERSION</td> - -<td>R</td> - -<td>String</td> - -<td>3</td> - -<td>"1.2"</td> -</tr> -</table></center> - -<dl><font size=-1>1. The first element of the array is the default -Palette.</font> -<br><font size=-1>2. This attribute is <b>required</b> for images -that use one of the standard color map types listed.</font> -<br><font size=-1>3. This attribute is <b>required</b> if set for the source -image, in the case that the image is translated from another file into -HDF5.</font> -<br><font size=-1>4. This applies to: IMAGE_SUBCLASS="IMAGE_GRAYSCALE" -or "IMAGE_BITMAP".</font> -<br><font size=-1>5. This applies to: IMAGE_SUBCLASS="IMAGE_GRAYSCALE", -"IMAGE_BITMAP", or "IMAGE_INDEXED".</font> -<br><font size=-1>6. This applies to: IMAGE_SUBCLASS="IMAGE_TRUECOLOR", -or "IMAGE_INDEXED".</font></dl> -</dl> -Table 2 summarizes the standard attributes for an Image datasets using -the common sub-classes. R means that the attribute listed on the leftmost -column is Required for the image subclass on the first row, O means that -the attribute is Optional for that subclass and N that the attribute cannot -be applied to that subclass. The two first rows show the only required -attributes -for all subclasses. -<br> -<table BORDER WIDTH="100%" > -<caption><b>Table 2a. Applicability of Attributes to IMAGE sub-classes</b></caption> - -<tr> -<td WIDTH="20%"><b>IMAGE_SUBCLASS</b><sup>1</sup></td> - -<td WIDTH="20%"><b>IMAGE_GRAYSCALE</b></td> - -<td WIDTH="20%"><b>IMAGE_BITMAP</b></td> -</tr> - -<tr> -<td WIDTH="20%">CLASS</td> - -<td WIDTH="20%">R</td> - -<td WIDTH="20%">R</td> -</tr> - -<tr> -<td WIDTH="20%">IMAGE_VERSION</td> - -<td WIDTH="20%">R</td> - -<td WIDTH="20%">R</td> -</tr> - -<tr> -<td>INTERLACE_MODE</td> - -<td>N</td> - -<td>N</td> -</tr> - -<tr> -<td WIDTH="20%">IMAGE_WHITE_IS_ZERO</td> - -<td WIDTH="20%">R</td> - -<td WIDTH="20%">R</td> -</tr> - -<tr> -<td WIDTH="20%">IMAGE_MINMAXRANGE</td> - -<td WIDTH="20%">O</td> - -<td WIDTH="20%">O</td> -</tr> - -<tr> -<td WIDTH="20%">IMAGE_BACKGROUNDINDEX</td> - -<td WIDTH="20%">O</td> - -<td WIDTH="20%">O</td> -</tr> - -<tr> -<td WIDTH="20%">IMAGE_TRANSPARENCY</td> - -<td WIDTH="20%">O</td> - -<td WIDTH="20%">O</td> -</tr> - -<tr> -<td WIDTH="20%">IMAGE_ASPECTRATIO</td> - -<td WIDTH="20%">O</td> - -<td WIDTH="20%">O</td> -</tr> - -<tr> -<td WIDTH="20%">IMAGE_COLORMODEL</td> - -<td WIDTH="20%">N</td> - -<td WIDTH="20%">N</td> -</tr> - -<tr> -<td WIDTH="20%">IMAGE_GAMMACORRECTION</td> - -<td WIDTH="20%">N</td> - -<td WIDTH="20%">N</td> -</tr> - -<tr> -<td WIDTH="20%">PALETTE</td> - -<td WIDTH="20%">O</td> - -<td WIDTH="20%">O</td> -</tr> - -<tr> -<td>DISPLAY_ORIGIN</td> - -<td>O</td> - -<td>O</td> -</tr> -</table> - -<blockquote> </blockquote> - -<table BORDER WIDTH="100%" > -<caption><b>Table 2b. Applicability of Attributes to IMAGE sub-classes</b></caption> - -<tr> -<td WIDTH="20%"><b>IMAGE_SUBCLASS</b></td> - -<td WIDTH="20%"><b>IMAGE_TRUECOLOR</b></td> - -<td><b>IMAGE_INDEXED</b></td> -</tr> - -<tr> -<td WIDTH="20%">CLASS</td> - -<td WIDTH="20%">R</td> - -<td>R</td> -</tr> - -<tr> -<td WIDTH="20%">IMAGE_VERSION</td> - -<td WIDTH="20%">R</td> - -<td>R</td> -</tr> - -<tr> -<td>INTERLACE_MODE</td> - -<td>R</td> - -<td>N</td> -</tr> - -<tr> -<td WIDTH="20%">IMAGE_WHITE_IS_ZERO</td> - -<td WIDTH="20%">N</td> - -<td>N</td> -</tr> - -<tr> -<td WIDTH="20%">IMAGE_MINMAXRANGE</td> - -<td WIDTH="20%">N</td> - -<td>O</td> -</tr> - -<tr> -<td WIDTH="20%">IMAGE_BACKGROUNDINDEX</td> - -<td WIDTH="20%">N</td> - -<td>O</td> -</tr> - -<tr> -<td WIDTH="20%">IMAGE_TRANSPARENCY</td> - -<td WIDTH="20%">N</td> - -<td>O</td> -</tr> - -<tr> -<td WIDTH="20%">IMAGE_ASPECTRATIO</td> - -<td WIDTH="20%">O</td> - -<td>O</td> -</tr> - -<tr> -<td WIDTH="20%">IMAGE_COLORMODEL</td> - -<td WIDTH="20%">O</td> - -<td>O</td> -</tr> - -<tr> -<td WIDTH="20%">IMAGE_GAMMACORRECTION</td> - -<td WIDTH="20%">O</td> - -<td>O</td> -</tr> - -<tr> -<td WIDTH="20%">PALETTE</td> - -<td WIDTH="20%">O</td> - -<td>O</td> -</tr> - -<tr> -<td>DISPLAY_ORIGIN</td> - -<td>O</td> - -<td>O</td> -</tr> -</table> - -<h3> -<a NAME="Section1.3"></a>1.3 Storage Layout and Properties for Images</h3> -In the case of an image with more than one component per pixel (e.g., Red, -Green, and Blue), the data may be arranged in one of two ways. Following -HDF4 terminology, the data may be interlaced by pixel or by plane, which -should be indicated by the INTERLACE_MODE attribute. In both -cases, the dataset will have a dataspace with three dimensions, height, -width, and components. The interlace modes specify different orders -for the dimensions. -<br> -<table BORDER COLS=2 WIDTH="100%" > -<caption><b>Table 3. Storage of multiple component image data.</b></caption> - -<tr> -<td><b>Interlace Mode</b></td> - -<td><b>Dimensions in the Dataspace</b></td> -</tr> - -<tr> -<td>INTERLACE_PIXEL</td> - -<td>[height][width][pixel components]</td> -</tr> - -<tr> -<td>INTERLACE_PLANE</td> - -<td>[pixel components][height][width]</td> -</tr> -</table> - -<p>For example, consider a 5 (rows) by 10 (column) image, with Red, Green, -and Blue components. Each component is an unsigned byte. In HDF5, -the datatype would be declared as an unsigned 8 bit integer. For -pixel interlace, the dataspace would be a three dimensional array, with -dimensions: [10][5][3]. For plane interleave, the dataspace would -be three dimensions: [3][10][5]. -<p>In the case of images with only one component, the dataspace may be -either a two dimensional array, or a three dimensional array with the third -dimension of size 1. For example, a 5 by 10 image with 8 bit color -indexes would be an HDF5 dataset with type unsigned 8 bit integer. -The dataspace could be either a two dimensional array, with dimensions -[10][5], or three dimensions, with dimensions either [10][5][1] or [1][10][5]. -<p>Image datasets may be stored with any chunking or compression properties -supported by HDF5. -<p><b>A note concerning compatibility with HDF5 GR interface: </b>An Image -dataset is stored as an HDF5 dataset. It is important to note that -the order of the dimensions is the same as for any other HDF5 dataset. -For a two dimensional image that is to be stored as a series of horizontal -scan lines, with the scan lines contiguous (i.e., the fastest changing -dimension is 'width'), the image will have a dataspace with <i>dim[0] = -height</i> and <i>dim[1]</i> = <i>width</i>. This is completely consistent -with all other HDF5 datasets. -<p>Users familiar with HDF4 should be cautioned that <i>this is not the -same as HDF4</i>, and specifically is not consistent with what the HDF4 -GR interface does. -<br> -<h2> -<a NAME="sect2"></a>2. HDF5 Palette Specification</h2> - -<h3> -2.1 Overview</h3> -A palette is the means by which color is applied to an image and is also -referred to as a color lookup table. It is a table in which every row contains -the numerical representation of a particular color. In the example of an -8 bit standard RGB color model palette, this numerical representation of -a color is presented as a triplet specifying the intensity of red, green, -and blue components that make up each color. -<center> -<p><img SRC="Palettes.fm.anc.gif" ></center> - -<p>In this example, the color component numeric type is an 8 bit unsigned -integer. While this is most common and recommended for general use, other -component color numeric datatypes, such as a 16 bit unsigned integer , -may be used. This type is specified as the type attribute of the palette -dataset. (see H5Tget_type(), H5Tset_type()) -<p>The minimum and maximum values of the component color numeric are specified -as attribute of the palette dataset. See below (attribute PAL_MINMAXNUMERIC). -If these attributes do not exist, it is assumed that the range of values -will fill the space of the color numeric type. i.e. with an 8 bit unsigned -integer, the valid range would be 0 to 255 for each color component. -<p>The HDF5 palette specification additionally allows for color models -beyond RGB. YUV, HSV, CMY, CMYK, YCbCr color models are supported, and -may be specified as a color model attribute of the palette dataset. <i>(see -"Palette Attributes" for details)</i>. -<p>In HDF 4 and earlier, palettes were limited to 256 colors. The HDF5 -palette specification allows for palettes of varying length. The length -is specified as the number of rows of the palette dataset. -<br> -<br> -<table BORDER COLS=1 WIDTH="100%" BGCOLOR="#666666" > -<tr> -<td><font color="#FFFFFF">Important Note: The specification of the Indexed -Palette will change substantially in the next version. The Palette -described here is <i>denigrated</i> and is not supported.</font></td> -</tr> -</table> - -<br> -<table BORDER COLS=1 WIDTH="100%" BGCOLOR="#CCCCCC" > -<tr> -<td><i>Denigrated</i> -<p>In a standard palette, the color entries are indexed directly. HDF5 -supports the notion of a range index table. Such a table defines an ascending -ordered list of ranges that map dataset values to the palette. If a range -index table exists for the palette, the PAL_TYPE attribute will be set -to "RANGEINDEX", and the PAL_RANGEINDEX attribute will contain an object -reference to a range index table array. If not, the PAL_TYPE attribute -either does not exist, or will be set to "STANDARD". -<p>The range index table array consists of a one dimensional array with -the same length as the palette dataset - 1. Ideally, the range index would -be of the same type as the dataset it refers to, however this is not a -requirement. -<p><b>Example 2: A range index array of type floating point</b> -<center> -<p><img SRC="PaletteExample1.gif" ></center> - -<p>The range index array attribute defines the "<i>to</i>" of the range. -Notice that the range index array attribute is one less entry in size than -the palette. The first entry of 0.1259, specifies that all values below -and up to 0.1259 inclusive, will map to the first palette entry. The second -entry signifies that all values greater than 0.1259 up to 0.3278 inclusive, -will map to the second palette entry, etc. All value greater than the last -range index array attribute (100000) map to the last entry in the palette.</td> -</tr> -</table> - -<h3> -<a NAME="sect2.2"></a>2.2. Palette Attributes</h3> -A palette exists in an HDF file as an independent data set with accompanying -attributes. The Palette attributes are scalars except where noted -otherwise. String values should have size the length of the string -value plus one. "Required" attributes must be used. "Optional" -attributes must be used when required. -<p>These attributes are defined as follows: -<dl> -<dt> -Attribute name="<b>CLASS</b>" (Required)</dt> - -<dd> -This attribute is of type H5T_C_S1, with size 7.</dd> - -<dd> -For all palettes, the value of this attribute is "PALETTE". This attribute -identifies this palette data set as a palette that conforms to the specifications -on this page.</dd> - -<dt> -Attribute name="<b>PAL_COLORMODEL</b>" (Required)</dt> - -<dd> -This attribute is of type H5T_C_S1, with size 3, 4, or 5.</dd> - -<dd> -Possible values for this are "RGB", "YUV", "CMY", "CMYK", "YCbCr", "HSV".</dd> - -<dd> -This defines the color model that the entries in the palette data set represent.</dd> - -<dl> -<dt> -"RGB"</dt> - -<dd> -Each color index contains a triplet where the the first value defines the -red component, second defines the green component, and the third the blue -component.</dd> - -<dt> -"CMY"</dt> - -<dd> -Each color index contains a triplet where the the first value defines the -cyan component, second defines the magenta component, and the third the -yellow component.</dd> - -<dt> -"CMYK"</dt> - -<dd> -Each color index contains a quadruplet where the the first value defines -the cyan component, second defines the magenta component, the third the -yellow component, and the forth the black component.</dd> - -<dt> -"YCbCr"</dt> - -<dd> -Class Y encoding model. Each color index contains a triplet where the the -first value defines the luminance, second defines the Cb Chromonance, and -the third the Cr Chromonance.</dd> - -<dt> -"YUV"</dt> - -<dd> -Composite encoding color model. Each color index contains a triplet where -the the first value defines the luminance component, second defines the -chromonance component, and the third the value component.</dd> - -<dt> -"HSV"</dt> - -<dd> -Each color index contains a triplet where the the first value defines the -hue component, second defines the saturation component, and the third the -value component. The hue component defines the hue spectrum with a low -value representing magenta/red progressing to a high value which would -represent blue/magenta, passing through yellow, green, cyan. A low value -for the saturation component means less color saturation than a high value. -A low value for <i>value</i> will be darker than a high value.</dd> - -<dd> -</dd> -</dl> - -<dt> -Attribute name="<b>PAL_TYPE</b>" (Required)</dt> - -<dd> -This attribute is of type H5T_C_S1, with size 9 or 10.</dd> - -<dd> -The current supported values for this attribute are : "STANDARD8" or "RANGEINDEX"</dd> - -<dd> -A PAL_TYPE of "STANDARD8" defines a palette dataset such that the first -entry defines index 0, the second entry defines index 1, etc. up until -the length of the palette - 1. This assumes an image dataset with direct -indexes into the palette.</dd> -</dl> - -<dl> -<table BORDER COLS=1 WIDTH="100%" BGCOLOR="#CCCCCC" > -<tr> -<td><i>Denigrated</i> -<p>If the PAL_TYPE is set to "RANGEINDEX", there will be an additional -attribute with a name of "<b>PAL_RANGEINDEX</b>", (See example 2 -for more details)</td> -</tr> -</table> - -<table BORDER COLS=1 WIDTH="100%" BGCOLOR="#CCCCCC" > -<tr> -<td> -<dt> -Attribute name="<b>PAL_RANGEINDEX</b>" <i>(Denigrated)</i></dt> - -<dl> -<dd> -The <b>PAL_RANGEINDEX</b> attribute contains an HDF object reference (HDF5 -datatype H5T_STD_REF_OBJ) pointer which specifies a range index array in -the file to be used for color lookups for the palette. (Only for -PAL_TYPE="RANGEINDEX")</dd> -</dl> -</td> -</tr> -</table> - -<dt> -Attribute name="<b>PAL_MINMAXNUMERIC</b>"</dt> - -<dl> -<dt> -If present, this attribute is an array of two numbers, of the same HDF5 -datatype as the palette elements or color numerics.</dt> - -<br>They specify the minimum and maximum values of the color numeric components. -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. -The intensity of the color guns would then be scaled accordingly to be -between this minimum and maximum attribute.</dl> -Attribute name="<b>PAL_VERSION</b>" (Required) -<dl>This attribute is of type H5T_C_S1, with size corresponding to the -length of the version string. This attribute identifies the version -number of this specification to which it conforms. The current version -is "1.2".</dl> - -<center><table BORDER=2 BGCOLOR="#FFFFFF" > -<caption><b>Table 4. Attributes of a Palette Dataset</b></caption> - -<tr> -<td><b>Attribute Name</b></td> - -<td><b>(R = Required,</b> -<br><b>O = Optional)</b></td> - -<td><b>Type</b></td> - -<td><b>String Size</b></td> - -<td><b>Value</b></td> -</tr> - -<tr> -<td>CLASS</td> - -<td>R</td> - -<td>String</td> - -<td> -<center>7</center> -</td> - -<td>"PALETTE"</td> -</tr> - -<tr> -<td>PAL_COLORMODEL</td> - -<td>R</td> - -<td>String</td> - -<td> -<center>3, 4, or 5</center> -</td> - -<td>Color Model: "RGB", YUV", "CMY", "CMYK", "YCbCr", or "HSV"</td> -</tr> - -<tr> -<td>PAL_TYPE</td> - -<td>R</td> - -<td>String</td> - -<td> -<center>9</center> - -<p><br> -<table BORDER COLS=1 WIDTH="100%" BGCOLOR="#CCCCCC" > -<tr> -<td>or 10</td> -</tr> -</table> -</td> - -<td>"STANDARD8" -<table BORDER COLS=1 WIDTH="100%" BGCOLOR="#CCCCCC" > -<tr> -<td>or "RANGEINDEX" <i>(Denigrated)</i></td> -</tr> -</table> -</td> -</tr> - -<tr> -<td> -<table BORDER COLS=1 WIDTH="100%" BGCOLOR="#CCCCCC" > -<tr> -<td><i>Denigrated</i> -<br>RANGE_INDEX</td> -</tr> -</table> -</td> - -<td></td> - -<td> -<table BORDER COLS=1 WIDTH="100%" BGCOLOR="#CCCCCC" > -<tr> -<td>Object Reference </td> -</tr> -</table> -</td> - -<td></td> - -<td> -<table BORDER COLS=1 WIDTH="100%" BGCOLOR="#CCCCCC" > -<tr> -<td><Object Reference to Dataset of range index values></td> -</tr> -</table> -</td> -</tr> - -<tr> -<td>PAL_MINMAXNUMERIC</td> - -<td>O</td> - -<td>Array[2] of <same datatype as palette></td> - -<td></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>4</td> - -<td>"1.2"</td> -</tr> -</table></center> - -<dl> -<table BORDER COLS=1 WIDTH="100%" BGCOLOR="#CCCCCC" > -<tr> -<td><font size=-1>1. The RANGE_INDEX attribute is required if the -PAL_TYPE is "RANGEINDEX". Otherwise, the RANGE_INDEX attribute should -be omitted. (Range index is denigrated.)</font></td> -</tr> -</table> -<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 minimum must be less than or equal to the value of the maximum.</font></dl> -</dl> -Table 5 summarized the uses of the standard attributes for a palette dataset. -R means that the attribute listed on the leftmost column is Required for -the palette type on the first row, O means that the attribute is Optional -for that type and N that the attribute cannot be applied to that type. -The four first rows show the attributes that are always required -for the two palette types. -<br> -<br> -<table BORDER WIDTH="100%" > -<caption><b>Table 5. Applicability of Attributes</b></caption> - -<tr> -<td WIDTH="33%"><b>PAL_TYPE</b></td> - -<td WIDTH="33%"><b>STANDARD8</b></td> - -<td WIDTH="34%"><b>RANGEINDEX</b></td> -</tr> - -<tr> -<td WIDTH="33%">CLASS</td> - -<td WIDTH="33%">R</td> - -<td WIDTH="34%">R</td> -</tr> - -<tr> -<td WIDTH="33%">PAL_VERSION</td> - -<td WIDTH="33%">R</td> - -<td WIDTH="34%">R</td> -</tr> - -<tr> -<td WIDTH="33%">PAL_COLORMODEL</td> - -<td WIDTH="33%">R</td> - -<td WIDTH="34%">R</td> -</tr> - -<tr> -<td WIDTH="33%">RANGE_INDEX</td> - -<td WIDTH="33%">N</td> - -<td WIDTH="34%">R</td> -</tr> - -<tr> -<td WIDTH="33%">PAL_MINMAXNUMERIC</td> - -<td WIDTH="33%">O</td> - -<td WIDTH="34%">O</td> -</tr> -</table> - -<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> -<a NAME="Sect3"></a>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 in a <b>PALETTE</b> attribute. This would be a 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 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. 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