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<!-- CreationDate: Mon Mar 13 18:03:10 2006 -->
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<head>
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<meta name="generator" content="groff -Thtml, see www.gnu.org">
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<meta name="Content-Style" content="text/css">
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<title>TIFFRGBAImage</title>
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</head>
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<body>
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<h1 align=center>TIFFRGBAImage</h1>
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<a href="#NAME">NAME</a><br>
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<a href="#SYNOPSIS">SYNOPSIS</a><br>
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<a href="#DESCRIPTION">DESCRIPTION</a><br>
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<a href="#ALTERNATE RASTER FORMATS">ALTERNATE RASTER FORMATS</a><br>
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<a href="#SIMULTANEOUS RASTER STORE AND DISPLAY">SIMULTANEOUS RASTER STORE AND DISPLAY</a><br>
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<a href="#SUPPORTING ADDITIONAL TIFF FORMATS">SUPPORTING ADDITIONAL TIFF FORMATS</a><br>
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<a href="#NOTES">NOTES</a><br>
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<a href="#RETURN VALUES">RETURN VALUES</a><br>
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<a href="#DIAGNOSTICS">DIAGNOSTICS</a><br>
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<a href="#SEE ALSO">SEE ALSO</a><br>
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<hr>
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<a name="NAME"></a>
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<h2>NAME</h2>
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<table width="100%" border=0 rules="none" frame="void"
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cols="2" cellspacing="0" cellpadding="0">
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<tr valign="top" align="left">
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<td width="8%"></td>
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<td width="91%">
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<p>TIFFRGBAImageOK, TIFFRGBAImageBegin, TIFFRGBAImageGet,
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TIFFRGBAImageEnd − read and decode an image into a
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raster</p>
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</td>
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</table>
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<a name="SYNOPSIS"></a>
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<h2>SYNOPSIS</h2>
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<table width="100%" border=0 rules="none" frame="void"
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cols="2" cellspacing="0" cellpadding="0">
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<tr valign="top" align="left">
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<td width="8%"></td>
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<td width="91%">
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<p><b>#include <tiffio.h></b></p>
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<p><b>typedef unsigned char TIFFRGBValue; typedef struct
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_TIFFRGBAImage TIFFRGBAImage;</b></p>
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<p><b>int TIFFRGBAImageOK(TIFF *</b><i>tif</i><b>, char</b>
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<i>emsg[1024]</i><b>)<br>
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int TIFFRGBAImageBegin(TIFFRGBAImage *</b><i>img</i><b>,
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TIFF*</b> <i>tif</i><b>, int</b> <i>stopOnError</i><b>,
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char</b> <i>emsg[1024]</i><b>)<br>
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int TIFFRGBAImageGet(TIFFRGBAImage *</b><i>img</i><b>,
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uint32*</b> <i>raster</i><b>, uint32</b> <i>width</i> <b>,
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uint32</b> <i>height</i><b>)<br>
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void TIFFRGBAImageEnd(TIFFRGBAImage
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*</b><i>img</i><b>)</b></p>
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</td>
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</table>
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<a name="DESCRIPTION"></a>
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<h2>DESCRIPTION</h2>
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<table width="100%" border=0 rules="none" frame="void"
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cols="2" cellspacing="0" cellpadding="0">
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<tr valign="top" align="left">
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<td width="8%"></td>
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<td width="91%">
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<p>The routines described here provide a high-level
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interface through which <small>TIFF</small> images may be
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read into memory. Images may be strip- or tile-based and
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have a variety of different characteristics: bits/sample,
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samples/pixel, photometric, etc. Decoding state is
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encapsulated in a <i>TIFFRGBAImage</i> structure making it
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possible to capture state for multiple images and quickly
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switch between them. The target raster format can be
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customized to a particular application’s needs by
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installing custom routines that manipulate image data
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according to application requirements.</p>
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<p>The default usage for these routines is: check if an
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image can be processed using <i>TIFFRGBAImageOK</i>,
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construct a decoder state block using
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<i>TIFFRGBAImageBegin</i>, read and decode an image into a
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target raster using <i>TIFFRGBAImageGet</i>, and then
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release resources using <i>TIFFRGBAImageEnd</i>.
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<i>TIFFRGBAImageGet</i> can be called multiple times to
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decode an image using different state parameters. If
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multiple images are to be displayed and there is not enough
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space for each of the decoded rasters, multiple state blocks
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can be managed and then calls can be made to
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<i>TIFFRGBAImageGet</i> as needed to display an image.</p>
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<p>The generated raster is assumed to be an array of
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<i>width</i> times <i>height</i> 32-bit entries, where
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<i>width</i> must be less than or equal to the width of the
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image (<i>height</i> may be any non-zero size). If the
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raster dimensions are smaller than the image, the image data
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is cropped to the raster bounds. If the raster height is
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greater than that of the image, then the image data are
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placed in the lower part of the raster. (Note that the
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raster is assume to be organized such that the pixel at
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location (<i>x</i>,<i>y</i>) is
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<i>raster</i>[<i>y</i>*<i>width</i>+<i>x</i>]; with the
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raster origin in the <b>lower-left</b> hand corner.)</p>
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<p>Raster pixels are 8-bit packed red, green, blue, alpha
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samples. The macros <i>TIFFGetR</i>, <i>TIFFGetG</i>,
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<i>TIFFGetB</i>, and <i>TIFFGetA</i> should be used to
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access individual samples. Images without Associated Alpha
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matting information have a constant Alpha of 1.0 (255).</p>
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<p><i>TIFFRGBAImageGet</i> converts non-8-bit images by
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scaling sample values. Palette, grayscale, bilevel,
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<small>CMYK</small> , and YCbCr images are converted to
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<small>RGB</small> transparently. Raster pixels are returned
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uncorrected by any colorimetry information present in the
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directory.</p>
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<!-- INDENTATION -->
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<p>The parameter <i>stopOnError</i> specifies how to act if
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an error is encountered while reading the image. If
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<i>stopOnError</i> is non-zero, then an error will terminate
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the operation; otherwise <i>TIFFRGBAImageGet</i> will
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continue processing data until all the possible data in the
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image have been requested.</p>
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</td>
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</table>
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<a name="ALTERNATE RASTER FORMATS"></a>
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<h2>ALTERNATE RASTER FORMATS</h2>
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<table width="100%" border=0 rules="none" frame="void"
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cols="2" cellspacing="0" cellpadding="0">
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<tr valign="top" align="left">
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<td width="8%"></td>
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<td width="91%">
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<p>To use the core support for reading and processing
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<small>TIFF</small> images, but write the resulting raster
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data in a different format one need only override the
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‘‘<i>put methods</i>’’ used to store
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raster data. These methods are are defined in the
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<i>TIFFRGBAImage</i> structure and initially setup by
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<i>TIFFRGBAImageBegin</i> to point to routines that pack
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raster data in the default <small>ABGR</small> pixel format.
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Two different routines are used according to the physical
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organization of the image data in the file:
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<i>PlanarConfiguration</i>=1 (packed samples), and
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<i>PlanarConfiguration</i>=2 (separated samples). Note that
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this mechanism can be used to transform the data before
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storing it in the raster. For example one can convert data
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to colormap indices for display on a colormap display.</p>
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</td>
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</table>
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<a name="SIMULTANEOUS RASTER STORE AND DISPLAY"></a>
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<h2>SIMULTANEOUS RASTER STORE AND DISPLAY</h2>
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<table width="100%" border=0 rules="none" frame="void"
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cols="2" cellspacing="0" cellpadding="0">
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<tr valign="top" align="left">
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<td width="8%"></td>
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<td width="91%">
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<p>It is simple to display an image as it is being read into
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memory by overriding the put methods as described above for
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supporting alternate raster formats. Simply keep a reference
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to the default put methods setup by
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<i>TIFFRGBAImageBegin</i> and then invoke them before or
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after each display operation. For example, the
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<i>tiffgt</i>(1) utility uses the following put method to
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update the display as the raster is being filled:</p>
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<pre>static void
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putContigAndDraw(TIFFRGBAImage* img, uint32* raster,
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uint32 x, uint32 y, uint32 w, uint32 h,
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int32 fromskew, int32 toskew,
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unsigned char* cp)
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{
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(*putContig)(img, raster, x, y, w, h, fromskew, toskew, cp);
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if (x+w == width) {
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w = width;
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if (img->orientation == ORIENTATION_TOPLEFT)
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lrectwrite(0, y-(h-1), w-1, y, raster-x-(h-1)*w);
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else
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lrectwrite(0, y, w-1, y+h-1, raster);
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}
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}
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</pre>
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<p>(the original routine provided by the library is saved in
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the variable <i>putContig</i>.)</p>
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</td>
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</table>
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<a name="SUPPORTING ADDITIONAL TIFF FORMATS"></a>
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<h2>SUPPORTING ADDITIONAL TIFF FORMATS</h2>
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<table width="100%" border=0 rules="none" frame="void"
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<tr valign="top" align="left">
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<td width="8%"></td>
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<td width="91%">
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<p>The <i>TIFFRGBAImage</i> routines support the most
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commonly encountered flavors of <small>TIFF.</small> It is
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possible to extend this support by overriding the
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‘‘<i>get method</i>’’ invoked by
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<i>TIFFRGBAImageGet</i> to read <small>TIFF</small> image
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data. Details of doing this are a bit involved, it is best
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to make a copy of an existing get method and modify it to
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suit the needs of an application.</p>
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</td>
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</table>
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<a name="NOTES"></a>
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<h2>NOTES</h2>
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<table width="100%" border=0 rules="none" frame="void"
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<tr valign="top" align="left">
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<td width="8%"></td>
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<td width="91%">
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<p>Samples must be either 1, 2, 4, 8, or 16 bits.
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Colorimetric samples/pixel must be either 1, 3, or 4 (i.e.
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<i>SamplesPerPixel</i> minus <i>ExtraSamples</i>).</p>
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<p>Palette image colormaps that appear to be incorrectly
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written as 8-bit values are automatically scaled to
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16-bits.</p>
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</td>
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</table>
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<a name="RETURN VALUES"></a>
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<h2>RETURN VALUES</h2>
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<table width="100%" border=0 rules="none" frame="void"
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<td width="8%"></td>
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<td width="91%">
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<p>All routines return 1 if the operation was successful.
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Otherwise, 0 is returned if an error was encountered and
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<i>stopOnError</i> is zero.</p>
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</td>
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</table>
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<a name="DIAGNOSTICS"></a>
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<h2>DIAGNOSTICS</h2>
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<table width="100%" border=0 rules="none" frame="void"
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<td width="8%"></td>
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<td width="91%">
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<p>All error messages are directed to the
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<i>TIFFError</i>(3TIFF) routine.</p>
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<p><b>Sorry, can not handle %d-bit pictures</b>. The image
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had <i>BitsPerSample</i> other than 1, 2, 4, 8, or 16.</p>
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<!-- INDENTATION -->
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<p><b>Sorry, can not handle %d-channel images</b>. The image
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had <i>SamplesPerPixel</i> other than 1, 3, or 4.</p>
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<!-- INDENTATION -->
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<p><b>Missing needed "PhotometricInterpretation"
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tag</b>. The image did not have a tag that describes how to
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display the data.</p>
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<p><b>No "PhotometricInterpretation" tag, assuming
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RGB</b>. The image was missing a tag that describes how to
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display it, but because it has 3 or 4 samples/pixel, it is
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assumed to be <small>RGB.</small></p>
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<p><b>No "PhotometricInterpretation" tag, assuming
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min-is-black</b>. The image was missing a tag that describes
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how to display it, but because it has 1 sample/pixel, it is
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assumed to be a grayscale or bilevel image.</p>
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<!-- INDENTATION -->
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<p><b>No space for photometric conversion table</b>. There
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was insufficient memory for a table used to convert image
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samples to 8-bit <small>RGB.</small></p>
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<!-- INDENTATION -->
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<p><b>Missing required "Colormap" tag</b>. A
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Palette image did not have a required <i>Colormap</i>
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tag.</p>
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<!-- INDENTATION -->
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<p><b>No space for tile buffer</b>. There was insufficient
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memory to allocate an i/o buffer.</p>
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<!-- INDENTATION -->
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<p><b>No space for strip buffer</b>. There was insufficient
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memory to allocate an i/o buffer.</p>
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<!-- INDENTATION -->
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<p><b>Can not handle format</b>. The image has a format
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(combination of <i>BitsPerSample</i>,
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<i>SamplesPerPixel</i>, and
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<i>PhotometricInterpretation</i>) that can not be
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handled.</p>
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<!-- INDENTATION -->
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<p><b>No space for B&W mapping table</b>. There was
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insufficient memory to allocate a table used to map
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grayscale data to <small>RGB.</small></p>
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<!-- INDENTATION -->
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<p><b>No space for Palette mapping table</b>. There was
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insufficient memory to allocate a table used to map data to
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8-bit <small>RGB.</small></p>
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</td>
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</table>
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<a name="SEE ALSO"></a>
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<h2>SEE ALSO</h2>
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<!-- INDENTATION -->
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<table width="100%" border=0 rules="none" frame="void"
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cols="2" cellspacing="0" cellpadding="0">
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<tr valign="top" align="left">
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<td width="8%"></td>
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<td width="91%">
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<p><b>TIFFOpen</b>(3TIFF), <b>TIFFReadRGBAImage</b>(3TIFF),
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<b>TIFFReadRGBAImageOriented</b>(3TIFF),
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<b>TIFFReadRGBAStrip</b>(3TIFF),
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<b>TIFFReadRGBATile</b>(3TIFF), <b>libtiff</b>(3TIFF)</p>
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<!-- INDENTATION -->
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<p>Libtiff library home page:
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<b>http://www.remotesensing.org/libtiff/</b></p>
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|
315 |
</td>
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316 |
</table>
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317 |
<hr>
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318 |
</body>
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319 |
</html>
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