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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 − 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 <tiffio.h></b></p> | |
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<p><b>#define TIFFGetR(abgr)</b></p> | |
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<p><b>((abgr) & 0xff)</b></p> | |
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<p><b>#define TIFFGetG(abgr)</b></p> | |
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<p><b>(((abgr) >> 8) & 0xff)</b></p> | |
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<p><b>#define TIFFGetB(abgr)</b></p> | |
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<p><b>(((abgr) >> 16) & 0xff)</b></p> | |
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<p><b>#define TIFFGetA(abgr)</b></p> | |
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<p><b>(((abgr) >> 24) & 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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<a name="DESCRIPTION"></a> | |
<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’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’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 "PhotometricInterpretation" | |
tag</b>. The image did not have a tag that describes how to | |
display the data.</p> | |
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<p><b>No "PhotometricInterpretation" 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 "PhotometricInterpretation" 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 "Colormap" 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&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.remotesensing.org/libtiff/</b></p> | |
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