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2 <!-- CreationDate: Sat Feb 24 18:37:17 2007 -->
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7 <title>TIFFReadScanline</title>
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10
11 <h1 align=center>TIFFReadScanline</h1>
12 <a href="#NAME">NAME</a><br>
13 <a href="#SYNOPSIS">SYNOPSIS</a><br>
14 <a href="#DESCRIPTION">DESCRIPTION</a><br>
15 <a href="#NOTES">NOTES</a><br>
16 <a href="#RETURN VALUES">RETURN VALUES</a><br>
17 <a href="#DIAGNOSTICS">DIAGNOSTICS</a><br>
18 <a href="#BUGS">BUGS</a><br>
19 <a href="#SEE ALSO">SEE ALSO</a><br>
20
21 <hr>
22 <a name="NAME"></a>
23 <h2>NAME</h2>
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30 <p>TIFFReadScanline &minus; read and decode a scanline of
31 data from an open <small>TIFF</small> file</p>
32 </td>
33 </table>
34 <a name="SYNOPSIS"></a>
35 <h2>SYNOPSIS</h2>
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42 <p><b>#include &lt;tiffio.h&gt;</b></p>
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44 <p><b>int TIFFReadScanline(TIFF *</b><i>tif</i><b>,
45 tdata_t</b> <i>buf</i><b>, uint32</b> <i>row</i><b>,
46 tsample_t</b> <i>sample</i><b>)</b></p>
47 </td>
48 </table>
49 <a name="DESCRIPTION"></a>
50 <h2>DESCRIPTION</h2>
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57 <p>Read the data for the specified row into the (user
58 supplied) data buffer <i>buf</i>. The data are returned
59 decompressed and, in the native byte- and bit-ordering, but
60 are otherwise packed (see further below). The buffer must be
61 large enough to hold an entire scanline of data.
62 Applications should call the routine <i>TIFFScanlineSize</i>
63 to find out the size (in bytes) of a scanline buffer. The
64 <i>row</i> parameter is always used by
65 <i>TIFFReadScanline</i>; the <i>sample</i> parameter is used
66 only if data are organized in separate planes
67 (<i>PlanarConfiguration</i>=2).</p>
68 </td>
69 </table>
70 <a name="NOTES"></a>
71 <h2>NOTES</h2>
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78 <p>The library attempts to hide bit- and byte-ordering
79 differences between the image and the native machine by
80 converting data to the native machine order. Bit reversal is
81 done if the <i>FillOrder</i> tag is opposite to the native
82 machine bit order. 16- and 32-bit samples are automatically
83 byte-swapped if the file was written with a byte order
84 opposite to the native machine byte order,</p>
85 <!-- INDENTATION -->
86 <p>In C++ the <i>sample</i> parameter defaults to 0.</p>
87 </td>
88 </table>
89 <a name="RETURN VALUES"></a>
90 <h2>RETURN VALUES</h2>
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97 <p><i>TIFFReadScanline</i> returns &minus;1 if it detects an
98 error; otherwise 1 is returned.</p>
99 </td>
100 </table>
101 <a name="DIAGNOSTICS"></a>
102 <h2>DIAGNOSTICS</h2>
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109 <p>All error messages are directed to the
110 <i>TIFFError</i>(3TIFF) routine.</p>
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112 <p><b>Compression algorithm does not support random
113 access</b>. Data was requested in a non-sequential order
114 from a file that uses a compression algorithm and that has
115 <i>RowsPerStrip</i> greater than one. That is, data in the
116 image is stored in a compressed form, and with multiple rows
117 packed into a strip. In this case, the library does not
118 support random access to the data. The data should either be
119 accessed sequentially, or the file should be converted so
120 that each strip is made up of one row of data.</p>
121 </td>
122 </table>
123 <a name="BUGS"></a>
124 <h2>BUGS</h2>
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131 <p>Reading subsampled YCbCR data does not work correctly
132 because, for <i>PlanarConfiguration</i>=2 the size of a
133 scanline is not calculated on a per-sample basis, and for
134 <i>PlanarConfiguration</i>=1 the library does not unpack the
135 block-interleaved samples; use the strip- and tile-based
136 interfaces to read these formats.</p>
137 </td>
138 </table>
139 <a name="SEE ALSO"></a>
140 <h2>SEE ALSO</h2>
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147 <p><b>TIFFOpen</b>(3TIFF),
148 <b>TIFFReadEncodedStrip</b>(3TIFF),
149 <b>TIFFReadRawStrip</b>(3TIFF), <b>libtiff</b>(3TIFF)</p>
150 <!-- INDENTATION -->
151 <p>Libtiff library home page:
152 <b>http://www.remotesensing.org/libtiff/</b></p>
153 </td>
154 </table>
155 <hr>
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