TIFF 6.0 Specification
Final—June 3, 1992
YC
b
C
r
Positioning = 1
YC
b
C
r
Positioning = 2
Luminance samples
Chrominance samples
Proper subsampling of the chrominance components incorporates an anti-aliasing
filter that reduces the spectral bandwidth of the full-resolution samples. The type
of filter used for subsampling determines the value of the YC
b
C
r
Positioning field.
For YC
b
C
r
Positioning = 1 (centered), subsampling of the chrominance compo-
nents can easily be accomplished using a symmetrical digital filter with an even
number of taps (coefficients). A commonly used filter for 2:1 subsampling utilizes
two taps (1/2,1/2).
For YC
b
C
r
Positioning = 2 (cosited), subsampling of the chrominance components
can easily be accomplished using a symmetrical digital filter with an odd number
of taps. A commonly used filter for 2:1 subsampling utilizes three taps (1/4,1/2,1/4).
The default value of this field is 1.
Ordering of Component Samples
This section defines the ordering convention used for Y, C
b
, and C
r
component
samples when the PlanarConfiguration field value = 1 (interleaving). For
PlanarConfiguration = 2, component samples are stored as 3 separate planes, and
the ordering is the same as that used for other PhotometricInterpretation field
values.
For PlanarConfiguration = 1, the component sample order is based on the subsam-
pling factors,
ChromaSubsampleHoriz
and
ChromaSubsampleVert,
defined by
the YC
b
C
r
SubSampling field. The image data within a TIFF file is comprised of
one or more “data units”, where a data unit is defined to be a sequence of samples:
• one or more Y samples
• a C
b
sample
• a C
r
sample
The Y samples within a data unit are specified as a two-dimensional array having
ChromaSubsampleVert
rows of
ChromaSubsampleHoriz
samples.
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