src/tiff/man/TIFFReadScanline.3tiff

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  25 .if n .po 0
  26 .TH TIFFReadScanline 3TIFF "October 15, 1995" "libtiff"
  27 .SH NAME
  28 TIFFReadScanline \- read and decode a scanline of data from an open
  29 .SM TIFF
  30 file
  31 .SH SYNOPSIS
  32 .B "#include <tiffio.h>"
  33 .sp
  34 .BI "int TIFFReadScanline(TIFF *" tif ", tdata_t " buf ", uint32 " row ", tsample_t " sample ")"
  35 .SH DESCRIPTION
  36 Read the data for the specified row into the (user supplied) data buffer
  37 .IR buf .
  38 The data are returned decompressed and, in the native byte- and bit-ordering,
  39 but are otherwise packed (see further below). The buffer must be large enough
  40 to hold an entire scanline of data. Applications should call the routine
  41 .IR TIFFScanlineSize
  42 to find out the size (in bytes) of a scanline buffer.
  43 The
  44 .I row
  45 parameter is always used by
  46 .IR TIFFReadScanline ;
  47 the
  48 .I sample
  49 parameter is used only if data are organized in separate planes (\c
  50 .IR PlanarConfiguration =2).
  51 .SH NOTES
  52 The library attempts to hide bit- and byte-ordering differences between the
  53 image and the native machine by converting data to the native machine order.
  54 Bit reversal is done if the
  55 .I FillOrder
  56 tag is opposite to the native machine bit order. 16- and 32-bit samples are
  57 automatically byte-swapped if the file was written with a byte order opposite
  58 to the native machine byte order,
  59 .PP
  60 In C++ the
  61 .I sample
  62 parameter defaults to 0.
  63 .SH "RETURN VALUES"
  64 .IR TIFFReadScanline
  65 returns \-1 if it detects an error; otherwise 1 is returned.
  66 .SH DIAGNOSTICS
  67 All error messages are directed to the
  68 .IR TIFFError (3TIFF)
  69 routine.
  70 .PP
  71 .BR "Compression algorithm does not support random access" .
  72 Data was requested in a non-sequential order from a file that uses a
  73 compression algorithm and that has
  74 .I RowsPerStrip
  75 greater than one.
  76 That is, data in the image is stored in a compressed form, and with multiple
  77 rows packed into a strip. In this case, the library does not support random
  78 access to the data. The data should either be accessed sequentially, or the
  79 file should be converted so that each strip is made up of one row of data.
  80 .SH BUGS
  81 Reading subsampled YCbCR data does not work correctly because, for
  82 .IR PlanarConfiguration =2
  83 the size of a scanline is not calculated on a per-sample basis, and for
  84 .IR PlanarConfiguration =1
  85 the library does not unpack the block-interleaved samples; use the strip- and
  86 tile-based interfaces to read these formats.
  87 .SH "SEE ALSO"
  88 .BR TIFFOpen (3TIFF),
  89 .BR TIFFReadEncodedStrip (3TIFF),
  90 .BR TIFFReadRawStrip (3TIFF),
  91 .BR libtiff (3TIFF)
  92 .PP
  93 Libtiff library home page:
  94 .BR http://www.remotesensing.org/libtiff/