TIFFReadScanline(3tiff)

1TIFFReadScanline(3TIFF)                                TIFFReadScanline(3TIFF)
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NAME

6       TIFFReadScanline - read and decode a scanline of data from an open TIFF
7       file
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SYNOPSIS

10       #include <tiffio.h>
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12       int TIFFReadScanline(TIFF *tif, tdata_t buf, uint32 row, tsample_t sam‐
13       ple)
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DESCRIPTION

16       Read  the data for the specified row into the (user supplied) data buf‐
17       fer buf.  The data are returned decompressed and, in the  native  byte-
18       and  bit-ordering,  but  are  otherwise packed (see further below). The
19       buffer must be large enough to hold an entire scanline of data.  Appli‐
20       cations  should  call the routine TIFFScanlineSize to find out the size
21       (in bytes) of a scanline buffer.  The row parameter is always  used  by
22       TIFFReadScanline;  the  sample parameter is used only if data are orga‐
23       nized in separate planes (PlanarConfiguration=2).
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NOTES

26       The library attempts to hide bit- and byte-ordering differences between
27       the  image  and  the  native  machine  by converting data to the native
28       machine order.  Bit reversal is done if the FillOrder tag  is  opposite
29       to  the  native machine bit order. 16- and 32-bit samples are automati‐
30       cally byte-swapped if the file was written with a byte  order  opposite
31       to the native machine byte order,
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33       In C++ the sample parameter defaults to 0.
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RETURN VALUES

36       TIFFReadScanline  returns  -1  if  it  detects an error; otherwise 1 is
37       returned.
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DIAGNOSTICS

40       All error messages are directed to the TIFFError(3TIFF) routine.
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42       Compression  algorithm  does  not  support  random  access.   Data  was
43       requested in a non-sequential order from a file that uses a compression
44       algorithm and that has RowsPerStrip greater than one.  That is, data in
45       the image is stored in a compressed form, and with multiple rows packed
46       into a strip. In this case, the library does not support random  access
47       to  the  data.  The data should either be accessed sequentially, or the
48       file should be converted so that each strip is made up of  one  row  of
49       data.
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BUGS

52       Reading subsampled YCbCR data does not work correctly because, for Pla‐
53       narConfiguration=2 the size of a scanline is not calculated on  a  per-
54       sample basis, and for PlanarConfiguration=1 the library does not unpack
55       the block-interleaved samples; use the strip- and tile-based interfaces
56       to read these formats.
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