153 lines
5.0 KiB
HTML
153 lines
5.0 KiB
HTML
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<meta name="generator" content="groff -Thtml, see www.gnu.org">
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<title>TIFFReadScanline</title>
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<body>
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<h1 align=center>TIFFReadScanline</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="#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="#BUGS">BUGS</a><br>
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<a href="#SEE ALSO">SEE ALSO</a><br>
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<hr>
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<!-- Creator : groff version 1.18 -->
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<!-- CreationDate: Mon Oct 7 17:36:20 2002 -->
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<a name="NAME"></a>
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<h2>NAME</h2>
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<p>TIFFReadScanline − read and decode a scanline of
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data from an open <small>TIFF</small> file</p>
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</td>
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</table></p>
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<a name="SYNOPSIS"></a>
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<h2>SYNOPSIS</h2>
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<p><b>#include <tiffio.h><br>
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int TIFFReadScanline(TIFF* tif, tdata_t buf, uint32 row,
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tsample_t sample)</b></p>
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</td>
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<a name="DESCRIPTION"></a>
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<h2>DESCRIPTION</h2>
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<p>Read the data for the specified row into the (user
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supplied) data buffer <i>buf</i>. The data are returned
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decompressed and, in the native byte- and bit-ordering, but
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are otherwise packed (see further below). The buffer must be
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large enough to hold an entire scanline of data.
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Applications should call the routine <i>TIFFScanlineSize</i>
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to find out the size (in bytes) of a scanline buffer. The
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<i>row</i> parameter is always used by
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<i>TIFFReadScanline</i>; the <i>sample</i> parameter is used
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only if data are organized in separate planes
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(<i>PlanarConfiguration</i>=2).</p>
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</td>
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<a name="NOTES"></a>
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<h2>NOTES</h2>
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<p>The library attempts to hide bit- and byte-ordering
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differences between the image and the native machine by
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converting data to the native machine order. Bit reversal is
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done if the <i>FillOrder</i> tag is opposite to the native
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machine bit order. 16- and 32-bit samples are automatically
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byte-swapped if the file was written with a byte order
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opposite to the native machine byte order,</p>
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<p>In C++ the <i>sample</i> parameter defaults to 0.</p>
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</td>
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</table></p>
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<a name="RETURN VALUES"></a>
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<h2>RETURN VALUES</h2>
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<td width="8%"></td>
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<td width="91%">
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<p><i>TIFFReadScanline</i> returns −1 if it detects an
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error; otherwise 1 is returned.</p>
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</td>
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</table></p>
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<a name="DIAGNOSTICS"></a>
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<h2>DIAGNOSTICS</h2>
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<p>All error messages are directed to the
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<i>TIFFError</i>(3T) routine.</p>
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<p><b>Compression algorithm does not support random
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access</b>. Data was requested in a non-sequential order
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from a file that uses a compression algorithm and that has
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<i>RowsPerStrip</i> greater than one. That is, data in the
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image is stored in a compressed form, and with multiple rows
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packed into a strip. In this case, the library does not
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support random access to the data. The data should either be
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accessed sequentially, or the file should be converted so
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that each strip is made up of one row of data.</p>
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</td>
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</table></p>
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<a name="BUGS"></a>
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<h2>BUGS</h2>
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<td width="8%"></td>
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<td width="91%">
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<p>Reading subsampled YCbCR data does not work correctly
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because, for <i>PlanarConfiguration</i>=2 the size of a
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scanline is not calculated on a per-sample basis, and for
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<i>PlanarConfiguration</i>=1 the library does not unpack the
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block-interleaved samples; use the strip- and tile-based
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interfaces to read these formats.</p>
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</td>
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</table></p>
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<a name="SEE ALSO"></a>
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<h2>SEE ALSO</h2>
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<td width="8%"></td>
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<td width="91%">
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<p><i>libtiff</i>(3T), <i>TIFFOpen</i>(3T),
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<i>TIFFReadEncodedStrip</i>(3T),
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<i>TIFFReadRawStrip</i>(3T)</p>
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</td>
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</table></p>
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<hr>
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</body>
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</html>
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