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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>revfix</title>
<meta http-equiv="content-type"
content="text/html; charset=ISO-8859-1">
<meta name="author" content="Graeme Gill">
</head>
<body>
<h2><b>xicc/revfix</b></h2>
<h3>Summary</h3>
Regenerate a CLUT device profiles B2A table data by inverting the A2B
table.<br>
<h3>Usage Summary</h3>
<small><span style="font-family: monospace;">revfix [-options] iccin
iccout</span><br style="font-family: monospace;">
<span style="font-family: monospace;"> -v
Verbose</span><br
style="font-family: monospace;">
<span style="font-family: monospace;"> -0
Process perceptual</span><br
style="font-family: monospace;">
<span style="font-family: monospace;"> -1
Process absolute/relative colorimetric</span><br
style="font-family: monospace;">
<span style="font-family: monospace;"> -2
Process saturation</span><br
style="font-family: monospace;">
<span style="font-family: monospace;"> -r res
Override BtoA1
CLUT res.</span><br style="font-family: monospace;">
<span style="font-family: monospace;"> </span><a
style="font-family: monospace;" href="#k">-k</a><span
style="font-family: monospace;"> [ezhxr]
e =
same K as existing BtoA table (def)</span><br
style="font-family: monospace;">
<span style="font-family: monospace;">
z =
zero, h = 0.5 K, x = max K, r = ramp K</span><br
style="font-family: monospace;">
<span style="font-family: monospace;"> </span><a
style="font-family: monospace;" href="#kp">-k p stle stpo enle enpo
shape</a><br style="font-family: monospace;">
<span style="font-family: monospace;">
p =
curve parameters</span><br style="font-family: monospace;">
<span style="font-family: monospace;">
stle: K
level at White 0.0 - 1.0</span><br style="font-family: monospace;">
<span style="font-family: monospace;">
stpo:
start point of transition Wh 0.0 - Bk 1.0</span><br
style="font-family: monospace;">
<span style="font-family: monospace;">
enpo:
End point of transition Wh 0.0 - Bk 1.0</span><br
style="font-family: monospace;">
<span style="font-family: monospace;">
enle: K level at Black 0.0 - 1.0</span><br
style="font-family: monospace;">
<span style="font-family: monospace;">
shape:
1.0 = straight, 0.0-1.0 concave, 1.0-2.0
convex</span><br style="font-family: monospace;">
<span style="font-family: monospace;"> </span><a
style="font-family: monospace;" href="#K">-K parameters</a><span
style="font-family: monospace;"> Same as
-k, but
target is K locus rather than K value itself</span><br
style="font-family: monospace;">
<span style="font-family: monospace;"> </span><a
style="font-family: monospace;" href="#l">-l tlimit</a><span
style="font-family: monospace;">
set total ink limit, 0
- 400%
(estimate by default)</span><br style="font-family: monospace;">
<span style="font-family: monospace;"> </span><a
style="font-family: monospace;" href="#L">-L klimit</a><span
style="font-family: monospace;">
set black ink limit, 0
- 100%
(estimate by default)</span><br style="font-family: monospace;">
<span style="font-family: monospace;"> </span><a
style="font-family: monospace;" href="#p">-p aprof.icm</a><span
style="font-family: monospace;">
Include abstract
profile in output tables</span></small><br>
<h3>Usage Details and Discussion</h3>
Existing ICC profiles may not contain accurately inverted AtoB table
data in their B2A tables, and this tool provides a means of
addressing this, or regenerating the B2A information with a different
black generation and/or ink limit, or applying an abstract correction
profile to the B2A table, without completely recreating the profile.<br>
<br>
Currently <b>revfix</b> does not support creating real perceptual or
saturation B2A tables, but can only create relative colorimetric
tables. It also will not handle CLUT profile that use a matrix element
in them.<br>
<br>
<b>-v</b> Turn on verbose mode. Gives progress information as the
table is created. Since B2A tables can take a long time to generate,
this is often useful to monitor progress.<br>
<br>
The B2A table to be re-creating can be specified by using the <b>-0</b>,
<b>-1</b>, and <b>-2</b>f lags. Normally only the <b>-1</b> flag
should be specified, but the perceptual and saturation tables can be
replaces instead/as well, if their respective flags are specified.<br>
<br>
Normally the re-created B2A table will have the same CLUT resolution as
the existing table, but this can be overridden by using the <b>-r</b>
flag.
Typically a resolution of 9 might be used for a medium quality CMYK
table,
with 17 being used for a high quality CMYK table. For an RGB profile, a
resolution of 17 might be used for a medium quality table, and 33 being
used for a high quality table.<br>
<tt></tt><br>
<a name="k"></a> -<b>k</b> parameter sets the target level of black (K)
when creating a B2A CMYK output tables. This is often called a black
level, a black inking rule, black generation, or under color
removal. These set the target black level.<br>
<br>
Possible arguments to the <b>-k</b> flag are:<br>
<br>
<b> -kz</b> selects minimum black (0.0)<br>
<b> -kh</b> selects a black value of 0.5<br>
<b> -kx</b> selects the maximum possible black (1.0)<br>
<b> -kr</b> selects a linear black ramp, starting at minimum black for
highlight, and maximum black for shadow (equivalent to -kp 0 0 1 1 1).
This is the default.<br>
<br>
<b><a name="kp"></a>-k p stle stpo enpo enle shape</b> allows an
arbitrary black value ramp to be defined, consisting of a starting
value (stle) for highlights, a breakpoint L value (stpo) where it
starts to transition to the shadow level, an end breakpoint L (enpo)
where it flattens out again, and the finishing black level (enle) for
the shadows. There is also a curve parameter, that modifies the
transition from stle to enle to either be concave (ie. the
transition starts gradually and and finished more abruptly) using
values 0.0-1.0, with 0.0 being most concave, or convex (the transition
starts more abruptly but finishes gradually), using values 1.0-2.0,
with 2.0 being the most convex.<br>
<br>
Typical black value generation curve with parameters something
like: -kp 0 .1 .9 1 .5<br>
<br>
<tt> 1.0 K |
enpo<br>
| _______
enle<br>
| /<br>
| /<br>
| /<br>
| /<br>
stle
| ------/<br>
+-------------------<br>
0.0 K
0.0 stpo 1.0<br>
White
Black<br>
</tt>
<br>
For minimum sensitivity of printed output to the lighting spectrum, it
currently seems best to use the maximum possible black, but other black
generation levels (ie. 0.3 to 0.5) may well be preferred if one wants
to
minimize the noisy appearance of black on an inkjet device, or
if the banding behaviour or other rendering flaws of the printer is to
be minimized. <br>
<br>
The <a href="xicclu.html">xicclu</a> tool can be used to plot out
the resulting black level for a given set of parameters, by using the <a
href="xicclu.html#g">-g</a> flag of a profile already created from the
same .ti3 file.<br>
<br>
<a name="K"></a> <span style="font-weight: bold;">-K parameters.</span>
Any of the <span style="font-weight: bold;">-k</span> options above
can use the <span style="font-weight: bold;">-K</span> version, in
which rather than a black value target being defined by the inking
rule, a black <span style="text-decoration: underline;">locus</span>
target is defined. For each lookup, the minimum possible black level
and the maximum possible black level is determined, the former
corresponding to a locus target of 0, and the latter corresponding to a
locus target of 1. For instance, at
the
white point, no black will be used in the output, even if the black
locus specifies a maximum (since the maximum amount of black that
can be used to print white is actually zero). Similarly, at the black
point, black may well be used, even if the black locus specifies
zero black (since a certain amount of black is needed to achieve the
desired density of color). <br>
<tt> </tt><br>
<a name="l"></a>The <b>-l</b> <i>tlimit</i> parameter sets the ink
limit (TAC, Total
Area Coverage) for the CMYK separation, as a total percentage from 0%
to 400%. By default, this value will be estimated from the profile. The
limit value should generally be set a little below the value used in
the test chart
generation, to avoid the very edges of the gamut. If the test chart ink
limit has been chosen to be a little beyond an acceptable level, then
this
number should be the acceptable level. Although limits can be set below
200%, this will generally restrict the color gamut noticeably, as fully
saturated
secondary colors will not be reproduced. Values are between 220% and
300%
for typical printing devices. The ink limit
will be in final calibrated device values if the profile includes
calibration information.<br>
<br>
<br>
<a name="L"></a> The <b>-L</b> <i>klimit</i> parameter sets the black
channel ink limit for the CMYK separation, as a total percentage from
0%
to 100%. By default, this value will be estimated from the profile. For
printing press like devices, this can be used to prevent
the
black channel screening pattern "filling in". Typical values might be
from
95% to 99%. The ink limit
will be in final calibrated device values if the profile includes
calibration information.<br>
<br>
<br>
The <b><a name="p"></a>-p</b> option allows specifying an abstract
profile be applied to all of the output tables. An abstract
profile is a way of specifying a color adjustment in a device
independent way. The abstract profile might have been created using one
of the <span style="font-weight: bold;">tweak</span> tools, such as <a
href="refine.html">refine</a>.<br>
<br>
<br>
<br>
<br>
<br>
</body>
</html>
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