TIFF 6.0 Specification
Final—June 3, 1992
C
r
= ( R - Y ) / ( 2 - 2 *
LumaRed
)
R, G, and B may be computed from YC
b
C
r
as follows:
R = C
r
* ( 2 - 2 *
LumaRed
) + Y
G = ( Y -
LumaBlue
* B -
LumaRed
* R ) /
LumaGreen
B = C
b
* ( 2 - 2 *
LumaBlue
) + Y
In disciplines such as printing, film, and video, there are practical reasons to pro-
vide footroom codes below the ReferenceBlack code and headroom codes above
ReferenceWhite code. In such cases the values of the transformation matrix used
to convert from YC
b
C
r
to RGB must be multiplied by a scale factor to produce
full-range RGB values. These scale factors depend on the reference ranges speci-
fied by the ReferenceBlackWhite field. See the ReferenceBlackWhite and
TransferFunction fields for more details.
The values coded by this field will typically reflect the transformation specified
by a standard for YC
b
C
r
encoding. The following table contains examples of com-
monly used values.
Standard
CCIR Recommendation 601-1
CCIR Recommendation 709
LumaRed
LumaGreen
LumaBlue
299 / 1000
587 / 1000 114 / 1000
2125 / 10000 7154 / 10000 721 / 10000
The default values for this field are those defined by CCIR Recommendation 601-
1: 299/1000, 587/1000 and 114/1000, for
LumaRed, LumaGreen
and
LumaBlue,
respectively.
YC
b
C
r
SubSampling
Tag
= 530 (212.H)
Type = SHORT
N
=2
Specifies the subsampling factors used for the chrominance components of a
YC
b
C
r
image. The two fields of this field,
YC
b
C
r
SubsampleHoriz
and
YC
b
C
r
SubsampleVert,
specify the horizontal and vertical subsampling factors
respectively.
The two fields of this field are defined as follows:
Short 0:
YC
b
C
r
SubsampleHoriz:
1 = ImageWidth of this chroma image is equal to the ImageWidth of the associated
luma image.
2 = ImageWidth of this chroma image is halfthe ImageWidth of the associated luma
image.
4 = ImageWidth of this chroma image is one-quarter the ImageWidth of the associ-
ated luma image.
Short 1:
YC
b
C
r
SubsampleVert:
1 = ImageLength (height) of this chroma image is equal to the ImageLength of the
associated luma image.
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