TIFF 6.0 Specification
Final—June 3, 1992
Organizational Changes
• To make the organization more consistent and expandable, appendices were
transformed into numbered sections.
• The document was divided into two parts—Baseline and Extensions—to help
developers make better and more consistent implementation choices. Part 1,
the Baseline section, describes those features that all general-purpose TIFF
readers should support. Part 2, the Extensions section, describes a number of
features that can be used by special or advanced applications.
• An index and table of contents were added.
Changes in Requirements
• To illustrate a Baseline TIFF file earlier in the document, the material from
Appendix G (“TIFF Classes”) in Revision 5 was integrated into the main body
of the specification . As part of this integration, the TIFF Classes terminology
was replaced by the more monolithic Baseline TIFF terminology. The intent
was to further encourage all mainstream TIFF readers to support the Baseline
TIFF requirements for bilevel, grayscale, RGB, and palette-color images.
• Due to licensing issues, LZW compression support was moved out of the “Part
1: Baseline TIFF” and into “Part 2: Extensions.”
• Baseline TIFF requirements for bit depths in palette-color images were weak-
ened a bit.
Changes in Terminology
In previous versions of the specification, the term “tag” reffered both to the identi-
fying number of a TIFF field and to the entire field. In this version, the term “tag”
refers only to the identifying number. The term “field” refers to the entire field,
including the value.
Compatibility
Every attempt has been made to add functionality in such a way as to minimize
compatibility problems with files and software that were based on earlier versions
of the TIFF specification. The goal is that TIFF files should never become obso-
lete and that TIFF software should not have to be revised more frequently than
absolutely necessary. In particular, Baseline TIFF 6.0 files will generally be read-
able even by older applications that assume TIFF 5.0 or an earlier version of the
specification.
However, TIFF 6.0 files that use one of the major new extensions, such as a new
compression scheme or color space, will not be successfully read by older soft-
ware. In such cases, the older applications must gracefully give up and refuse to
import the image, providing the user with a reasonably informative message.
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