xicc/tiffgamut
Summary
Create a gamut file or VRML file of the color gamut of the
contents of a set of TIFF image.
tiffgamut allows creation of
gamut files from the pixel values in a
set of TIFF raster images, as defined by an ICC profile, in L*a*b* or
CIECAM02
Jab
colorspace, and can also represent the gamut as a VRML file. This
can be used for visualizing and comparing the gamut of an image to the
colorspace it is
in, or a colorspace it might get transformed into, and can also be used
to create an image source gamut for use with
collink.
NOTE that if you are creating
an image gamut suitable for use with the collink
-g or -G
flags, or colprof
-g, use the Jab appearance space intent for appearance space gamut
mappings, and the same input viewing
conditions to be used in collink
or colprof
using
the -c flag, i.e. "tiffgamut -pj -cmt sRGB.icm image.tif"
Usage Summary
tiffgamut [-v level]
[profile.icm | embedded.tif] infile1.tif [infile2.tif ...]
-v
Verbose
-d
sres Surface
resolution details 1.0 - 50.0
-w
emit VRML .wrl file as well as CGATS .gam file
-n
Don't add VRML axes or white/black point
-k
Add markers for prim. & sec. "cusp" points
-f perc Filter by popularity,
perc = percent to use
-i
intent p =
perceptual, r = relative colorimetric,
s = saturation, a = absolute (default), d = profile default
-o
order n = normal
(priority: lut > matrix > monochrome)
r = reverse (priority: monochrome >
matrix > lut)
-p oride l =
Lab_PCS (default), j = CIECAM02 Appearance Jab
-c viewcond set
appearance mode and viewing conditions for CIECAM02,
either an enumerated choice, or a parameter:value change
pp - Practical Reflection Print
pe - Print evaluation environment
mt - Monitor in typical work environment
mb - Monitor in bright work environment
md - Monitor in darkened work
environment
jm - Projector in dim environment
jd - Projector in dark environment
pcd - Photo CD - original scene
outdoors
ob - Original scene - Bright Outdoors
cx - Cut Sheet Transparencies on a viewing box
s:surround a = average, m = dim, d = dark,
c = transparency (default average)
w:X:Y:Z Adapted white point
as XYZ (default media white)
w:x:y Adapted white point as
x, y
a:adaptation Adaptation luminance in
cd.m^2
(default 50.0)
b:background Background % of image luminance (default 20)
f:flare Flare
light % of image luminance (default 1)
f:X:Y:Z Flare color as
XYZ (default media white)
f:x:y Flare color as x, y
-O outputfile Override the default output filename &
extension.
Usage Details and Discussion
The -v flag dumps out the ICC profile header information.
The -d parameter controls the level of detail displayed in the
surface. The parameter roughly corresponds to a deltaE value, so
smaller
values
give greater detail. The default value is around 10, and is a good
place
to start. Small values may take a lot of time to generate, and will
produce
big files.
The -w flag causes a VRML file to be produced, as well as a
gamut file.
The -n flag suppresses the L*a*b* axes being created in
the
VRML.
The -k flag adds markers for
each of the primary and secondary "cusp" points (Red, Yellow, Green,
Cyan, Blue & Magenta). No markers will be displayed if the cusps
cannot be determined.
The -f perc parameter turns on filtering of
the raster colors. The colors from the image are clustered, and then
sorted according to popularity, and then the perc most common percentage of
colors are used to create the gamut surface. This may be useful in
creating a source gamut mapping surface that favors the important
colors within an image, and doesn't attempt to compress the color
reproduction in order to reproduce the little used colors. A value of perc of 90 or 80 may be a good place
to start. Note that the filtering is performed independently on each
raster image processed, with the final gamut being the union of all the
filtered image gamuts.
The -i flag selects the intent transform used for a lut based
profile. It also selects between relative and absolute colorimetric for
non-lut base profiles. Note that anything other than colorimetric may
not represent the
native capabilities of the device. The default intent will be absolute
colorimetic for L*a*b* output, and CIECAM02 appearance for Jab output.
An ICC profile is allowed to contain more than the minimum number of
elements or table needed to describe a certain transform, and may
contain redundant descriptions. By default, LUT based table
information will be used first if present, followed by matrix/shaper
information, and only using monochrome
information if it is all that is present. The -o flag, reverses
this
order.
-p: By default the gamut will
be created in L*a*b* colorspace. If -pj is selected, then CIECAM02
appearance space Jab will be used for the output, and the viewing
conditions will be taken into account. Jab space is what is normally
needed to be compatible with the default intents used in colprof.
Note that the CIECAM02 output space selection by default uses
the colorimetric transform of the profile resulting in the appearance
of the native device, but that the perceptual or
saturation transforms may be used by selecting them using the -i parameter, which may give a
different result with some profiles. This may be desirable if an image
is to be transformed through the perceptual or saturation tables of a
profile as part of a link with an Argyll generated output profile,
since it will then represent the apparent gamut of the image when
subject to these tables. If the absolute colorimetric intent is chosen
using -ia in combinations with
-pj, then Jab with
a fixed white reference is used, which emulates an absolute CIECAM02
Jab
appearance space.
The -c parameter sets the
output space to CIECAM02 appearance Jab values, and also allows
choosing
a set of viewing conditions, either by choosing a typical viewing
environment, or controlling
particular viewing condition parameters. This is only functional if an
ICC profile is provided.
The -O parameter allows the
output file name & extension to be specified independently of the
last tiff
filename. Note that the full filename must be specified, including the
extension.
If the TIFF files are in a device space (ie. RGB, CMYK etc.), then it
is
necessary to supply an ICC profile to translate the device space values
to a CIE space value such as L*a*b* or CIECAM02 Jab space for creating
a gamut surface. For the ICC profile provided it is then possible to
select exactly what type of conversion is used. A TIFF file with an
embeded ICC profile may be supplied as the profile argument - e.g. to
get the gamut of a tiff file that contains an embedded profile use
something like:
tiffgamut image.tif image.tif
If a TIFF file is
already in a CIE space such as CIELab or ICCLab, then it is not
necessary to select an ICC profile, although a PCS to PCS
colorspace profile may be chosen. All the TIFF files
must be in the same colorspace.
One or more TIFF files may be specified, and the gamut is the union of
the gamuts of each file. This is useful for creating an image specific
gamut mapping that can be applied to a set of images with consistent
results between the images. Note that the output gamut file name will
by default be taken from the last TIFF file specified, with the .gam
extension added automatically. The -O
parameter will override this default.
NOTES
The white and black points put in the gamut are the colorspace white
and black points. For the purposes of latter gamut mapping, it is
assumed that the image should retain it's position within the
colorspace dynamic range. For an L*a*b* image, the values value 100,0,0
and 0,0,0 for white and black are assumed. An image in L*a*b* should be
adjusted be neutral to, and sit within the dynamic range of those white
and black points.