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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>printcal</title>
<meta http-equiv="content-type" content="text/html;
charset=windows-1252">
<meta name="author" content="Graeme W. Gill">
</head>
<body>
<h2> profile/printcal</h2>
<h3>Summary</h3>
Create a printer linearization calibration file from <a
href="File_Formats.html#.ti3">.ti3</a> test chart patch values.<br>
<br>
This is often very useful in preparing a raw printer for profiling,
by establishing per-channel ink limits, and linearizing the channel
response.<br>
It is typically not so useful when used with "RGB" printers, since
these already have a well controlled response, and the RGB channels
are not native colorant channels.<br>
<h3>Usage Summary</h3>
<span style="font-family: monospace;">printcal</span><small
style="font-family: monospace;"> [-<i>options</i>] [prevcal]
inoutfile<br>
<a href="#v">-v verbosity</a>
Set verbosity level<br>
</small><small style="font-family: monospace;"> <a href="#p">-p
[2]</a> Plot
graphs.<br>
<a moz-do-not-send="true" href="#w">-w</a>
Save colorant 3D plot to inoutname_r.x3d.html and
inoutname_c.x3d.html<br>
<a href="#i">-i</a>
Initial calibration, set targets,
create .cal<br>
</small><small style="font-family: monospace;"> <a href="#r">-r</a>
Re-calibrate against previous .cal and create new
.cal</small><br style="font-family: monospace;">
<span style="font-family: monospace;"></span><small
style="font-family: monospace;"> <a href="#e">-e</a>
Verify against previous .cal<br>
</small><small style="font-family: monospace;"> <a href="#I">-I</a>
Create imitation target from .ti3 and null
calibration<br>
</small><small style="font-family: monospace;"><tt>
</tt></tt></small> <small style="font-family: monospace;"><a
href="#d">-d</a>
Go through the motions but don't write
any files<br>
<a moz-do-not-send="true" href="#z">-z</a>
res
Resolution of created calibration curves (default 256)<br>
<a moz-do-not-send="true" href="#s">-s</a>
smoothing Extra curve
smoothing (default 1.0)<br style="font-family: monospace;">
</small> <small><span style="font-family: monospace;"> </span><a
style="font-family: monospace;" href="#A">-A "manufacturer"</a><span
style="font-family: monospace;"> Set the manufacturer
description string</span><br style="font-family: monospace;">
<span style="font-family: monospace;"> </span><a
style="font-family: monospace;" href="#M">-M "model"</a><span
style="font-family: monospace;">
Set the model
description string</span><br style="font-family: monospace;">
<span style="font-family: monospace;"> </span><a
style="font-family: monospace;" href="#D">-D "description"</a><span
style="font-family: monospace;"> Set the profile
Description string </span><br style="font-family: monospace;">
<tt> </tt><tt><a href="#C">-C "copyright"</a></tt><tt>
Set the copyright string</tt><tt><br>
</tt><tt> </tt><tt> </tt><tt><a href="#x">-x# percent</a></tt><tt>
Set
initial
maximum device % target (override auto)</tt><tt><br>
</tt></small><small><span style="font-family: monospace;"><small> <a
href="#m">-m# percent</a>
Set initial dev target to % of auto maximum<br>
</small> <a href="#n">-n# deltaE</a>
Set initial white
minimum deltaE target<br>
<a href="#t">-t# percent</a>
Set
initial
50% transfer curve percentage target<br style="font-family:
monospace;">
<span style="font-family: monospace;"> # = c, r,
0 First channel</span><br
style="font-family: monospace;">
<span style="font-family: monospace;">
m,
g,
1
Second channel</span><br style="font-family: monospace;">
<span style="font-family: monospace;">
y,
b,
2
Third channel</span><br style="font-family: monospace;">
<span style="font-family: monospace;">
k,
3
Fourth
channel, etc.<br>
<a href="#a">-a</a>
Create
an
Adobe Photoshop .AMP file as well as a .cal<br
style="font-family: monospace;">
</span><span style="font-family: monospace;"> </span><a
style="font-family: monospace;" href="#p1">prevcal</a><span
style="font-family: monospace;">
Base
name
of previous .cal file for recal or verify.</span><br
style="font-family: monospace;">
<span style="font-family: monospace;"> </span><a
style="font-family: monospace;" href="#p2">inoutname</a><span
style="font-family: monospace;">
Base
name
of input .ti3 file, output .cal file</span><br>
</span><span style="font-family: monospace;"></span></small><small><span
style="font-family: monospace;"></span><span style="font-family:
monospace;"></span><span style="font-family: monospace;"></span></small><br>
<h3>Options<br>
</h3>
<b><a name="v"></a>-v</b> Turn on verbose mode. Gives progress
information as the calibration is created. An argument greater than
1 increases the verbosity. An argument of 2 or greater will also
dump various curve values. Setting verbose will report the ideal
power value to apply to the test chart in targen.<br>
<br>
<a name="p"></a><span style="font-weight: bold;">-p</span> Turns on
plot mode. This causes various graphs to be plotted as the
calibration is created. The channels will be plotted in the graph
colors: Blue, Red, Yellow, Black, Green, Purple, Brown, Orange,
Grey, White. Using <b>-p 2</b> will display extra graphs, such as
relative to absolute Delta E equivalence, and fit of the raw
measurement data.<br>
<br>
<a name="w"></a><span style="font-weight: bold;">-w</span> Save
colorant 3D plot to inoutname_r.x3d.html and inoutname_c.x3d.html.
The first plot is the uncalibrated colorant response, with each cone
representing a 5% increment of raw device values. The second plot is
the calibrated and maximum device value limited response, with each
cone representing 5% increments of the calibrated device values.
Both these plots are in L*a*b* space.<br>
<br>
<a name="i"></a><span style="font-weight: bold;">-i</span> Select
initial calibration mode. Initial calibration mode allows setting
the targets for the calibration, such as maximum device percentage,
minimum white level, and the transfer curve shape. The second last
parameter <span style="font-weight: bold;"><span
style="font-weight: bold;"></span>prevcal</span> is not used in
this mode.<br>
<br>
<a name="r"></a><span style="font-weight: bold;">-r</span> Turns on
re-calibration mode. This is used for calibrations after the initial
one, where the aim is to return the devices response to the same
state as it was after the initial caibration. Parameters that affect
the calibration targets are ignored. The second last parameter <span
style="font-weight: bold;"><span style="font-weight: bold;"></span>prevcal</span>
is used to establish what the targets for the calibration are.<br>
<br>
<a name="e"></a><span style="font-weight: bold;">-e</span> Turns on
verify mode. In this mode the test chart input is verified against
the expected response in the <span style="font-weight: bold;"><span
style="font-weight: bold;"></span>prevcal</span> file. This
means that the test chart <u>has to be printed</u> with the
calibration curves active in the workflow. <b>Note</b> that if a
calibration is created that sets any <small><span
style="font-family: monospace;"><a href="#n"
moz-do-not-send="true">-n# deltaE</a> </span></small>parameters,
then a verification will probably fail, since the trajectories of
each ink from a non-white media color were not actually measured in
the initial calibration.<span style="font-family: monospace;"></span><br>
<br>
<a name="I"></a><span style="font-weight: bold;">-I</span> Similar
to <span style="font-weight: bold;">-i</span>, except that rather
than creating a linear target curve and corresponding calibration,
it takes the given behaviour as an absolute target and create a
corresponding set of calibration curves. This .cal can then be used
to recalibrate a similar device (or the same device at some other
time) to imitate the behaviour of the initial device. The second
last parameter <span style="font-weight: bold;"><span
style="font-weight: bold;"></span>prevcal</span> is not used in
this mode. Parameters that affect the calibration targets are
ignored.<br>
<br>
<a name="d"></a><span style="font-weight: bold;">-d</span> Disables
the writing of any files, causing printcal to go through the motions
without changing anything.<br>
<br>
<a name="z"></a>The <b>-z</b> parameter allows setting the
resolution of the created calibration curves.<br>
<br>
<a name="s"></a>The <b>-s</b> parameter allows setting smoothing
applied to the measured points in creating curves. The default value
is 1.0, and increasing this value (say to 1.5, or 2.0 etc.) will
increase the smoothness at the cost of accuracy. <br>
<br>
<a name="A"></a>The <b>-A</b> parameter allows setting of the
device manufacturer description string in the calibration file. The
parameter should be a string that identifies the manufacturer of the
device being profiled. With most command line shells, it will be
necessary to enclose the parameter with double quotes, so that
spaces and other special characters are included in the parameter,
and not mistaken for the start of another flag or as a final command
line parameters. By default no device manufacturer description
string will be put in the calibration file.<br>
<br>
<a name="M"></a>The <b>-M</b> parameter allows setting of the
device mode description string in the calibration file. The
parameter should be a string that identifies the particular model of
device being profiled. With most command line shells, it will be
necessary to enclose the parameter with double quotes, so that
spaces and other special characters are included in the parameter,
and not mistaken for the start of another flag or as a final command
line parameters. By default no model description string will be put
in the calibration file.<br>
<br>
<a name="D"></a>The <b>-D</b> parameter allows setting of the
profile description string in the calibration file. The parameter
should be a string that describes the device and profile. On many
systems, it will be this string that will be used to identify the
profile from a list of possible profiles. With most command line
shells, it will be necessary to enclose the parameter with double
quotes, so that spaces and other special characters are included in
the parameter, and not mistaken for the start of another flag or as
a final command line parameter. By default no profile description
string will be put in the calibration file.<br>
<br>
<a name="C"></a>The <b>-C</b> parameter allows setting of the
profile copyright string in the calibration file. The parameter
should be a string that describes the copyright (if any) claimed on
the profile being generated. With most command line shells, it will
be necessary to enclose the parameter with double quotes, so that
spaces and other special characters are included in the parameter,
and not mistaken for the start of another flag or as a final command
line parameters. By default no copyright string will be put in the
calibration file.<br>
<br>
<a name="x"></a> The <b>-x</b> parameter allows overriding the
default auto maximum device target value computed from the raw
device response for the initial calibration. The default uses a
heuristic to decide when the response of the device to each channels
colorant value reaches the point of diminishing returns, while the <span
style="font-weight: bold;">-x</span> parameter allows this default
to be overridden. The <span style="font-weight: bold;">-x</span>
parameter can be used multiple times, once for each channel that is
being set. The <span style="font-weight: bold;">-x</span> should be
followed by the channel number between 0 and 15, or the aliases <span
style="font-weight: bold;">r</span>, <span style="font-weight:
bold;">g</span> or <span style="font-weight: bold;">g</span>, or
<span style="font-weight: bold;">c</span>, <span
style="font-weight: bold;">m</span>, <span style="font-weight:
bold;">y</span> or <span style="font-weight: bold;">k,</span> and
the channel number should then be followed by the device value as a
percentage. <span style="font-weight: bold;">NOTE</span> that you
will probably get sub-optimal results if you force a device maximum
that is beyond the point of maximum response of a device channel,
since this will have the effect of <span style="text-decoration:
underline;">reducing</span> the device response. If you want to
set a conservative target to allow for recalibration later, see the
<b>-m</b> flag below.<br>
<br>
<a name="m"></a> The <b>-m</b> parameter allows modifying the
default auto maximum device target value for the initial
calibration. The auto maximum is computed as described above, and is
then scaled by the <b>-m</b> parameter value. Typically this will
be a scale down (ie. <b>90%</b>) to allow some margin to increase
the channel value if the channel density drops in a future
recalibration. Scaling the maximum down will reduce gamut, but
allows scope for stable behaviour using calibration. The <span
style="font-weight: bold;">-m</span> paramater can be used
multiple times, once for each channel that is being set. The <span
style="font-weight: bold;">-m</span> should be followed by the
channel number between 0 and 15, or the aliases <span
style="font-weight: bold;">r</span>, <span style="font-weight:
bold;">g</span> or <span style="font-weight: bold;">g</span>, or
<span style="font-weight: bold;">c</span>, <span
style="font-weight: bold;">m</span>, <span style="font-weight:
bold;">y</span> or <span style="font-weight: bold;">k,</span> and
the channel number should then be followed by the deltaE value.<span
style="font-family: monospace;"></span><br>
<br>
<a name="n"></a> The <b>-n</b> parameter allows overriding the
default minimum deltaE of a colorant to white of 0. This can be used
to set a minimum colorant level in order to emulate media darker or
of a different tint. The <span style="font-weight: bold;">-n</span>
paramater can be used multiple times, once for each channel that is
being set. The <span style="font-weight: bold;">-n</span> should be
followed by the channel number between 0 and 15, or the aliases <span
style="font-weight: bold;">r</span>, <span style="font-weight:
bold;">g</span> or <span style="font-weight: bold;">g</span>, or
<span style="font-weight: bold;">c</span>, <span
style="font-weight: bold;">m</span>, <span style="font-weight:
bold;">y</span> or <span style="font-weight: bold;">k,</span> and
the channel number should then be followed by the deltaE value.<br>
<b>Note</b> that setting a minimum deltaE will probably lead to some
degree of mismatch when attempting to <u>verify</u> a calibration,
since the trajectories of each ink from a non-white media color were
not actually measured in the initial calibration.<span
style="font-family: monospace;"></span><br>
<br>
<a name="t"></a> The <b>-t</b> parameter allows setting a target
linearization curve that is other than purely visual linear. The
default is to create a calibration curve that results in a perfectly
even change in output for each change in the calibrated device
value, as measured by steps in delta E94. The <span
style="font-weight: bold;">-t</span> parameter allows setting a
target curve above or below the perfectly visual linear, by setting
the aim value at 50% input. An aim higher than 50% will cause that
channel to become more intense by the 50% mark, while a value lower
than 50% will cause the channel to become less intense by the 50%
mark than perfectly linear.The <span style="font-weight: bold;">-t</span>
should be followed by the channel number between 0 and 15, or the
aliases <span style="font-weight: bold;">r</span>, <span
style="font-weight: bold;">g</span> or <span style="font-weight:
bold;">g</span>, or <span style="font-weight: bold;">c</span>, <span
style="font-weight: bold;">m</span>, <span style="font-weight:
bold;">y</span> or <span style="font-weight: bold;">k,</span> and
the channel number should then be followed by the device value as a
percentage.<br>
<br>
<a name="a"></a><span style="font-weight: bold;">-a</span> Creates
an Adobe Photoshop <span style="font-weight: bold;">.AMP</span>
format curves file as well as a .cal.<br>
<span style="font-weight: bold;"></span><br>
<a name="p1"></a> The optional second last parameter is the file
base name for a previous <a href="File_Formats.html#CAL">.cal</a>
calibration file, used as the target reference for recalibrate and
verify modes. <br>
<br>
<a name="p2"></a> The final parameter is the file base name for the
<a href="File_Formats.html#.ti3">.ti3</a> input test point data, and
the resulting <a href="File_Formats.html#CAL">.cal</a> calibration
file output. <br>
<h3><a name="DISCUSSION"></a>Discussion</h3>
<span style="font-weight: bold;">Printcal</span> is a tool for
creating per device channel linearization curves for printing
devices.<br>
<br>
As input it takes a .ti3 file containing the results of printing a
test chart on the <span style="text-decoration: underline;">non-color
managed</span>, <span style="text-decoration: underline;">non-calibrated</span>
device, and measuring it. The test chart should consists of step
wedges for each of the device primary colors, from the media white
to full individual colorant intensity.<br>
<br>
For the initial calibration (<span style="font-weight: bold;">-i</span>),
the
range
of device values to be used and the shape of the target
linearization curve are established, as well as creating the first
set of calibration curves. For subsequent re-calibrations (<span
style="font-weight: bold;">-r</span>), the calibration curves aim
to reproduce the same response as the original calibration. If a
test chart is printed with calibration enabled in the worklflow and
then is measured, it can be used to verify the calibration against
the expected response (<span style="font-weight: bold;">-e</span>).<br>
<br>
As each colorant steps through the test wedge patches from media
white, they trace out a measured locus in CIE L*a*b* colorspace.
Each channel response is evaluated by computing the CIE DeltaE to
media white of the response to a change in each individual channel
of each locus. This measure is used to determine when the devices
response to a colorant level is reaching diminishing returns,
setting a maximum colorant value. This measure can also be used to
set a minimum colorant value for the purposes of emulating a
different media color. The default maximum and minimum values for
each colorant can be overridden using the <span style="font-weight:
bold;">-x</span> and <span style="font-weight: bold;">-n</span>
parameters. The automatically determined maximum may be modified
(scaled) using the <b>-m</b> parameter, which can be useful in
allowing some margin for future calibrations to compensate for a
drop in density.<br>
<br>
The actual linearization uses a subtly different measure, which is
the CIE DelataE 94 along each colorant response locus, ensuring that
after linearization each step in colorant value is subjectively
even. The linearization aim can be altered from a purely linear
curve by using the <span style="font-weight: bold;"><span
style="font-weight: bold;">-t</span></span> parameters.<br>
<br>
After the initial calibration, the device can be re-calibrated (<span
style="font-weight: bold;">-r</span>) by printing a calibration
test chart under the same conditions as the initial one, but with
the calibration aimed at reproducing the same response as the
initial calibration, rather that setting new targets.<br>
<br>
The calibration can be verified (<span style="font-weight: bold;">-e</span>)
by printing a calibration test chart on <span
style="text-decoration: underline;">non-color managed</span>, <span
style="text-decoration: underline;"></span>but calibrated device,
the verification evaluating any discrepancy between the device
response achieved, and the device response expected. For a numerical
evaluation the verbose flag (<span style="font-weight: bold;">-v</span>)
should be used, and for a visual evaluation the plot flag (<span
style="font-weight: bold;">-p</span>) should be used. <b>Note</b>
that if a calibration is created that sets any <small><span
style="font-family: monospace;"><a href="#n"
moz-do-not-send="true">-n# deltaE</a> </span></small>parameters,
then a verification will probably fail, since the trajectories of
each ink from a non-white media color were not actually measured in
the initial calibration.<br>
<br>
If there are several devices of the same or similar model, then one
device can be used to set the initial calibration target, and then
the other devices can be re-calibrated against the same .cal file,
to create matching responses.<br>
<br>
An alternative to creating an initial linear target for calibration,
is to use the <span style="font-weight: bold;">-I</span> option
with an initial device, which sets the initial target to be that
devices absolute response. Naturally the corresponding calibration
will be linear (null). The calibration target can then be used with
a recalibrate to return that device to its initial response, or to
make another similar device have the same response. Note though,
that bad things will happen if the imitated devices response is
non-monotonic, or if on re-calibration the device is unable to reach
the same density levels.<br>
<br>
<br>
<br>
<br>
<br>
<br>
<br>
<br>
<br>
<br>
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