libtiff/html/man/TIFFReadRGBATile.3tiff.html
Bob Friesenhahn c3402403ea * html/man/Makefile.am (htmldoc): Fix htmldoc rule so that it can
be used if build directory is not the same as source directory.
* man/{TIFFGetField.3tiff, man/TIFFSetField.3tiff}: Documented
TIFFTAG_PHOTOSHOP, TIFFTAG_RICHTIFFIPTC, and TIFFTAG_XMLPACKET,
and re-sorted tag names in alphabetical order.
2006-01-02 23:50:44 +00:00

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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>
<hr>
<a name="NAME"></a>
<h2>NAME</h2>
<p style="margin-left:11%; margin-top: 1em">TIFFReadRGBATile
&minus; read and decode an image tile into a fixed-format
raster</p>
<a name="SYNOPSIS"></a>
<h2>SYNOPSIS</h2>
<p style="margin-left:11%; margin-top: 1em"><b>#include
&lt;tiffio.h&gt;</b></p>
<table width="100%" border=0 rules="none" frame="void"
cellspacing="0" cellpadding="0">
<tr valign="top" align="left">
<td width="11%"></td>
<td width="-3%">
<p valign="top"><b>#define TIFFGetR(abgr)</b></p></td>
<td width="30%"></td>
<td width="8%"></td>
<td width="54%">
<p valign="top"><b>((abgr) &amp; 0xff)</b></p></td>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="-3%">
<p valign="top"><b>#define TIFFGetG(abgr)</b></p></td>
<td width="30%"></td>
<td width="8%"></td>
<td width="54%">
<p valign="top"><b>(((abgr) &gt;&gt; 8) &amp; 0xff)</b></p></td>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="-3%">
<p valign="top"><b>#define TIFFGetB(abgr)</b></p></td>
<td width="30%"></td>
<td width="8%"></td>
<td width="54%">
<p valign="top"><b>(((abgr) &gt;&gt; 16) &amp;
0xff)</b></p> </td>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="-3%">
<p valign="top"><b>#define TIFFGetA(abgr)</b></p></td>
<td width="30%"></td>
<td width="8%"></td>
<td width="54%">
<p valign="top"><b>(((abgr) &gt;&gt; 24) &amp;
0xff)</b></p> </td>
</table>
<p style="margin-left:11%; margin-top: 1em"><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>
<a name="DESCRIPTION"></a>
<h2>DESCRIPTION</h2>
<p style="margin-left:11%; margin-top: 1em"><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>
<p style="margin-left:11%; margin-top: 1em">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>
<p style="margin-left:11%; margin-top: 1em">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>
<p style="margin-left:11%; margin-top: 1em">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>
<p style="margin-left:11%; margin-top: 1em">See the
<i>TIFFRGBAImage</i>(3TIFF) page for more details on how
various image types are converted to RGBA values.</p>
<a name="NOTES"></a>
<h2>NOTES</h2>
<p style="margin-left:11%; margin-top: 1em">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>
<p style="margin-left:11%; margin-top: 1em">Palette image
colormaps that appear to be incorrectly written as 8-bit
values are automatically scaled to 16-bits.</p>
<p style="margin-left:11%; margin-top: 1em"><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>
<a name="RETURN VALUES"></a>
<h2>RETURN VALUES</h2>
<p style="margin-left:11%; margin-top: 1em">1 is returned
if the image was successfully read and converted. Otherwise,
0 is returned if an error was encountered.</p>
<a name="DIAGNOSTICS"></a>
<h2>DIAGNOSTICS</h2>
<p style="margin-left:11%; margin-top: 1em">All error
messages are directed to the <i>TIFFError</i>(3TIFF)
routine.</p>
<p style="margin-left:11%; margin-top: 1em"><b>Sorry, can
not handle %d-bit pictures</b>. The image had
<i>BitsPerSample</i> other than 1, 2, 4, 8, or 16.</p>
<p style="margin-left:11%; margin-top: 1em"><b>Sorry, can
not handle %d-channel images</b>. The image had
<i>SamplesPerPixel</i> other than 1, 3, or 4.</p>
<p style="margin-left:11%; margin-top: 1em"><b>Missing
needed &quot;PhotometricInterpretation&quot; tag</b>. The
image did not have a tag that describes how to display the
data.</p>
<p style="margin-left:11%; margin-top: 1em"><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>
<p style="margin-left:11%; margin-top: 1em"><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>
<p style="margin-left:11%; margin-top: 1em"><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>
<p style="margin-left:11%; margin-top: 1em"><b>Missing
required &quot;Colormap&quot; tag</b>. A Palette image did
not have a required <i>Colormap</i> tag.</p>
<p style="margin-left:11%; margin-top: 1em"><b>No space for
tile buffer</b>. There was insufficient memory to allocate
an i/o buffer.</p>
<p style="margin-left:11%; margin-top: 1em"><b>No space for
strip buffer</b>. There was insufficient memory to allocate
an i/o buffer.</p>
<p style="margin-left:11%; margin-top: 1em"><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>
<p style="margin-left:11%; margin-top: 1em"><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>
<p style="margin-left:11%; margin-top: 1em"><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>
<a name="SEE ALSO"></a>
<h2>SEE ALSO</h2>
<p style="margin-left:11%; margin-top: 1em"><b>TIFFOpen</b>(3TIFF),
<b>TIFFRGBAImage</b>(3TIFF),
<b>TIFFReadRGBAImage</b>(3TIFF),
<b>TIFFReadRGBAStrip</b>(3TIFF), <b>libtiff</b>(3TIFF)</p>
<p style="margin-left:11%; margin-top: 1em">Libtiff library
home page: <b>http://www.remotesensing.org/libtiff/</b></p>
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