src/tiff/man/TIFFReadScanline.3tiff

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