TIFF 6.0 Specification
Final—June 3, 1992
Comments on the Bilevel Image Example
• The IFD in this example starts at 14h. It could have started anywhere in the file
providing the offset was an even number greater than or equal to 8 (since the
TIFF header is always the first 8 bytes of a TIFF file).
• With 16 rows per strip, there are 188 strips in all.
• The example uses a number of optional fields such as DateTime. TIFF readers
must safely skip over these fields if they do not understand or do not wish to
use the information. Baseline TIFF readers must not require that such fields be
present.
• To make a point, this example has highly-fragmented image data. The strips of
the image are not in sequential order. The point of this example is to illustrate
that strip offsets must not be ignored. Never assume that strip N+1 follows
strip N on disk. It is not required that the image data follow the IFD informa-
tion.
Required Fields for Bilevel Images
Here is a list of required fields for Baseline TIFF bilevel images. The fields are
listed in numerical order, as they would appear in the IFD. Note that the previous
example omits some of these fields. This is permitted because the fields that were
omitted each have a default and the default is appropriate for this file.
TagName
ImageWidth
ImageLength
Compression
PhotometricInterpretation
StripOffsets
RowsPerStrip
StripByteCounts
XResolution
YResolution
ResolutionUnit
Decimal Hex
256
257
259
262
273
278
279
282
283
296
100
101
103
106
111
116
117
11A
11B
128
Type
SHORT or LONG
SHORT or LONG
SHORT
SHORT
SHORT or LONG
SHORT or LONG
LONG or SHORT
RATIONAL
RATIONAL
SHORT
Value
1, 2 or 32773
0 or 1
1, 2 or 3
Baseline TIFF bilevel images were called TIFF Class B images in earlier versions
of the TIFF specification.
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