src/tiff/man/TIFFReadDirectory.3tiff

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  24 .if n .po 0
  25 .TH TIFFReadDirectory 3TIFF "October 15, 1995" "libtiff"
  26 .SH NAME
  27 TIFFReadDirectory \- get the contents of the next directory in an open
  28 .SM TIFF
  29 file
  30 .SH SYNOPSIS
  31 .B "#include <tiffio.h>"
  32 .sp
  33 .BI "int TIFFReadDirectory(TIFF *" tif ")"
  34 .SH DESCRIPTION
  35 Read the next directory in the specified file and make it the current
  36 directory. Applications only need to call
  37 .I TIFFReadDirectory
  38 to read multiple subfiles in a single
  39 .SM TIFF
  40 file\(em
  41 the first directory in a file is automatically read when
  42 .IR TIFFOpen
  43 is called.
  44 .SH NOTES
  45 If the library is compiled with
  46 .SM STRIPCHOP_SUPPORT
  47 enabled, then images that have a single uncompressed strip or tile of data are
  48 automatically treated as if they were made up of multiple strips or tiles of
  49 approximately 8 kilobytes each. This operation is done only in-memory; it does
  50 not alter the contents of the file. However, the construction of the ``chopped
  51 strips'' is visible to the application through the number of strips [tiles]
  52 returned by
  53 .I TIFFNumberOfStrips
  54 [\c
  55 .IR TIFFNumberOfTiles ].
  56 .SH "RETURN VALUES"
  57 If the next directory was successfully read, 1 is returned. Otherwise, 0 is
  58 returned if an error was encountered, or if there are no more directories to
  59 be read.
  60 .SH DIAGNOSTICS
  61 All error messages are directed to the
  62 .IR TIFFError (3TIFF)
  63 routine.
  64 All warning messages are directed to the
  65 .IR TIFFWarning (3TIFF)
  66 routine.
  67 .PP
  68 \fBSeek error accessing TIFF directory\fP.
  69 An error occurred while positioning to the location of the
  70 directory.
  71 .PP
  72 \fBWrong data type %d for field "%s"\fP.
  73 The tag entry in the directory had an incorrect data type.
  74 For example, an
  75 .I ImageDescription
  76 tag with a
  77 .SM SHORT
  78 data type.
  79 .PP
  80 \fBTIFF directory is missing required "%s" field\fP.
  81 The specified tag is required to be present by the
  82 .SM TIFF
  83 5.0 specification, but is missing.
  84 The directory is (usually) unusable.
  85 .PP
  86 \fB%s: Rational with zero denominator\fP.
  87 A directory tag has a
  88 .SM RATIONAL
  89 value whose denominator is zero.
  90 .PP
  91 \fBIncorrect count %d for field "%s" (%lu, expecting %lu); tag ignored\fP.
  92 The specified tag's count field is bad.
  93 For example, a count other than 1 for a
  94 .I SubFileType
  95 tag.
  96 .PP
  97 \fBCannot handle different per-sample values for field "%s"\fP.
  98 The tag has
  99 .I SamplesPerPixel
 100 values and they are not all the same; e.g.
 101 .IR BitsPerSample .
 102 The library is unable to handle images of this sort.
 103 .PP
 104 \fBCount mismatch for field "%s"; expecting %d, got %d\fP.
 105 The count field in a
 106 tag does not agree with the number expected by the library.
 107 This should never happen, so if it does, the library refuses to
 108 read the directory.
 109 .PP
 110 \fBInvalid TIFF directory; tags are not sorted in ascending order\fP.
 111 The directory tags are not properly sorted as specified
 112 in the
 113 .SM TIFF
 114 5.0 specification.
 115 This error is not fatal.
 116 .PP
 117 \fBIgnoring unknown field with tag %d (0x%x)\fP.
 118 An unknown tag was encountered in the directory;
 119 the library ignores all such tags.
 120 .PP
 121 \fBTIFF directory is missing required "ImageLength" field\fP.
 122 The image violates the specification by not having a necessary field.
 123 There is no way for the library to recover from this error.
 124 .PP
 125 \fBTIFF directory is missing required "PlanarConfig" field\fP.
 126 The image violates the specification by not having a necessary field.
 127 There is no way for the library to recover from this error.
 128 .PP
 129 \fBTIFF directory is missing required "StripOffsets" field\fP.
 130 The image has multiple strips, but is missing the tag that
 131 specifies the file offset to each strip of data.
 132 There is no way for the library to recover from this error.
 133 .PP
 134 \fBTIFF directory is missing required "TileOffsets" field\fP.
 135 The image has multiple tiles, but is missing the tag that
 136 specifies the file offset to each tile of data.
 137 There is no way for the library to recover from this error.
 138 .PP
 139 \fBTIFF directory is missing required "StripByteCounts" field\fP.
 140 The image has multiple strips, but is missing the tag that
 141 specifies the size of each strip of data.
 142 There is no way for the library to recover from this error.
 143 .PP
 144 \fBTIFF directory is missing required "StripByteCounts" field, calculating from imagelength\fP.
 145 The image violates the specification by not having a necessary field.
 146 However, when the image is comprised of only one strip or tile, the
 147 library will estimate the missing value based on the file size.
 148 .PP
 149 \fBBogus "StripByteCounts" field, ignoring and calculating from imagelength\fP.
 150 Certain vendors violate the specification by writing zero for
 151 the StripByteCounts tag when they want to leave the value
 152 unspecified.
 153 If the image has a single strip, the library will estimate
 154 the missing value based on the file size.
 155 .SH "SEE ALSO"
 156 .BR TIFFOpen (3TIFF),
 157 .BR TIFFWriteDirectory (3TIFF),
 158 .BR TIFFSetDirectory (3TIFF),
 159 .BR TIFFSetSubDirectory (3TIFF),
 160 .BR libtiff (3TIFF)
 161 .PP
 162 Libtiff library home page:
 163 .BR http://www.remotesensing.org/libtiff/