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<!-- Creator : groff version 1.18.1 -->
<!-- CreationDate: Sat Feb 24 18:37:17 2007 -->
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<title>TIFFReadRGBATile</title>
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<h1 align=center>TIFFReadRGBATile</h1>
<a href="#NAME">NAME</a><br>
<a href="#SYNOPSIS">SYNOPSIS</a><br>
<a href="#DESCRIPTION">DESCRIPTION</a><br>
<a href="#NOTES">NOTES</a><br>
<a href="#RETURN VALUES">RETURN VALUES</a><br>
<a href="#DIAGNOSTICS">DIAGNOSTICS</a><br>
<a href="#SEE ALSO">SEE ALSO</a><br>
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<a name="NAME"></a>
<h2>NAME</h2>
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<p>TIFFReadRGBATile &minus; read and decode an image tile
into a fixed-format raster</p>
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<a name="SYNOPSIS"></a>
<h2>SYNOPSIS</h2>
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<p><b>#include &lt;tiffio.h&gt;</b></p>
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<p><b>#define TIFFGetR(abgr)</b></p>
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<p><b>((abgr) &amp; 0xff)</b></p>
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<p><b>#define TIFFGetG(abgr)</b></p>
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<p><b>(((abgr) &gt;&gt; 8) &amp; 0xff)</b></p>
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<p><b>#define TIFFGetB(abgr)</b></p>
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<p><b>(((abgr) &gt;&gt; 16) &amp; 0xff)</b></p>
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<p><b>#define TIFFGetA(abgr)</b></p>
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<p><b>(((abgr) &gt;&gt; 24) &amp; 0xff)</b></p>
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<p><b>int TIFFReadRGBATile(TIFF *</b><i>tif</i><b>,
uint32</b> <i>x</i><b>, uint32</b> <i>y</i><b>, uint32
*</b><i>raster</i><b>)</b></p>
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<h2>DESCRIPTION</h2>
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<p><i>TIFFReadRGBATile</i> reads a single tile of a
tile-based image into memory, storing the result in the user
supplied RGBA <i>raster</i>. The raster is assumed to be an
array of width times length 32-bit entries, where width is
the width of a tile (TIFFTAG_TILEWIDTH) and length is the
height of a tile (TIFFTAG_TILELENGTH).</p>
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<p>The <i>x</i> and <i>y</i> values are the offsets from the
top left corner to the top left corner of the tile to be
read. They must be an exact multiple of the tile width and
length.</p>
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<p>Note that the raster is assume to be organized such that
the pixel at location (<i>x</i>,<i>y</i>) is
<i>raster</i>[<i>y</i>*<i>width</i>+<i>x</i>]; with the
raster origin in the <i>lower-left hand corner</i> of the
tile. That is bottom to top organization. Edge tiles which
partly fall off the image will be filled out with
appropriate zeroed areas.</p>
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<p>Raster pixels are 8-bit packed red, green, blue, alpha
samples. The macros <i>TIFFGetR</i>, <i>TIFFGetG</i>,
<i>TIFFGetB</i>, and <i>TIFFGetA</i> should be used to
access individual samples. Images without Associated Alpha
matting information have a constant Alpha of 1.0 (255).</p>
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<p>See the <i>TIFFRGBAImage</i>(3TIFF) page for more details
on how various image types are converted to RGBA values.</p>
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<a name="NOTES"></a>
<h2>NOTES</h2>
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<p>Samples must be either 1, 2, 4, 8, or 16 bits.
Colorimetric samples/pixel must be either 1, 3, or 4 (i.e.
<i>SamplesPerPixel</i> minus <i>ExtraSamples</i>).</p>
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<p>Palette image colormaps that appear to be incorrectly
written as 8-bit values are automatically scaled to
16-bits.</p>
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<p><i>TIFFReadRGBATile</i> is just a wrapper around the more
general <i>TIFFRGBAImage</i>(3TIFF) facilities. It&rsquo;s
main advantage over the similar <i>TIFFReadRGBAImage()</i>
function is that for large images a single buffer capable of
holding the whole image doesn&rsquo;t need to be allocated,
only enough for one tile. The <i>TIFFReadRGBAStrip()</i>
function does a similar operation for stripped images.</p>
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<a name="RETURN VALUES"></a>
<h2>RETURN VALUES</h2>
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<p>1 is returned if the image was successfully read and
converted. Otherwise, 0 is returned if an error was
encountered.</p>
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<a name="DIAGNOSTICS"></a>
<h2>DIAGNOSTICS</h2>
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<p>All error messages are directed to the
<i>TIFFError</i>(3TIFF) routine.</p>
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<p><b>Sorry, can not handle %d-bit pictures</b>. The image
had <i>BitsPerSample</i> other than 1, 2, 4, 8, or 16.</p>
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<p><b>Sorry, can not handle %d-channel images</b>. The image
had <i>SamplesPerPixel</i> other than 1, 3, or 4.</p>
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<p><b>Missing needed &quot;PhotometricInterpretation&quot;
tag</b>. The image did not have a tag that describes how to
display the data.</p>
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<p><b>No &quot;PhotometricInterpretation&quot; tag, assuming
RGB</b>. The image was missing a tag that describes how to
display it, but because it has 3 or 4 samples/pixel, it is
assumed to be <small>RGB.</small></p>
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<p><b>No &quot;PhotometricInterpretation&quot; tag, assuming
min-is-black</b>. The image was missing a tag that describes
how to display it, but because it has 1 sample/pixel, it is
assumed to be a grayscale or bilevel image.</p>
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<p><b>No space for photometric conversion table</b>. There
was insufficient memory for a table used to convert image
samples to 8-bit <small>RGB.</small></p>
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<p><b>Missing required &quot;Colormap&quot; tag</b>. A
Palette image did not have a required <i>Colormap</i>
tag.</p>
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<p><b>No space for tile buffer</b>. There was insufficient
memory to allocate an i/o buffer.</p>
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<p><b>No space for strip buffer</b>. There was insufficient
memory to allocate an i/o buffer.</p>
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<p><b>Can not handle format</b>. The image has a format
(combination of <i>BitsPerSample</i>,
<i>SamplesPerPixel</i>, and
<i>PhotometricInterpretation</i>) that
<i>TIFFReadRGBAImage</i> can not handle.</p>
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<p><b>No space for B&amp;W mapping table</b>. There was
insufficient memory to allocate a table used to map
grayscale data to <small>RGB.</small></p>
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<p><b>No space for Palette mapping table</b>. There was
insufficient memory to allocate a table used to map data to
8-bit <small>RGB.</small></p>
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<a name="SEE ALSO"></a>
<h2>SEE ALSO</h2>
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<p><b>TIFFOpen</b>(3TIFF), <b>TIFFRGBAImage</b>(3TIFF),
<b>TIFFReadRGBAImage</b>(3TIFF),
<b>TIFFReadRGBAStrip</b>(3TIFF), <b>libtiff</b>(3TIFF)</p>
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<p>Libtiff library home page:
<b>http://www.simplesystems.org/libtiff/</b></p>
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