On Wed, 2008-01-23 at 17:09 -0600, Leonard Evens wrote:
> Gimp 2.4.3 allows color proofing but provides no mechanism for using a
> printer profile to actually print.   I presume there are weighty issues
> involved in doing such a thing.
> But in principle, it is not to difficult to do it in an ad hoc manner.
> All you have to do is modify the image using the print profile to do so
> and then print the result.  I've managed to do it as follows.  I created
> my print profile using a measuring device and the argyll suite of
> command line programs.  argyll also includes a program cctiff for
> modifying a tiff file given source and destination profiles.   The lcms
> package also contains a similar program tifficc (also jpegicc).   I've
> used both these programs to modify a tiff file (assuming sRGB as the
> source profile) and then printed them using photoprint.   I'm pretty
> sure that I could also do the printing using a gimp print plugin, in my
> case, the gimp gutenprint plugin.
> One does have to exercise a little care.  First you have to make sure
> you let the profile do the work and print "uncorrected", and also, you
> have to use the same printing scheme to print that you used for making
> the profile.
> Measuring devices which can read prints are a bit expensive, so not
> everyone will want to go that route, but there are people who will
> produce a profile for you at modest cost.  Look in particular at
> www.blackfiveservices.co.uk/photoprint.shtml

I've since learned more about this matter from different sources.

I will try to describe it, but my discussion may still contain some
inaccuracies, and I hope I will be corrected, with attendant detail,
where necessary.

There may be some advantage to using photoprint and letting it do
everything, including conversions from profiles.  Namely, although it
seems that all the conversion programs do their arithmetic with the same
high precision, programs such as cctiff will yield a file with 8 bit
depth if you start with such a file (as, for example, output from gimp).
That is what you will send to the printer. But photoprint, as I
understand it, even if presented with an 8 bit depth file, will send the
printer information in 16 bit depth. There won't be any intermediate
rounding before doing so.  This may make some difference, depending on
what the printer driver does

Of course, one could convert the gimp file with 8 bit depth to an image
with 16 bit depth using ImageMagick, and then apply cctiff to get a 16
bit depth result.  But then you would have to find a means of printing
the image without losing whatever advantage 16 bit depth might offer at
that point. I haven't yet figured out exactly how to do this without
using photoprint, in which case you might as well have it handle the
profiles. But is is clearly possible to do.  All one has to do is create
a tool which does the same thing photoprint does without having to go
its interface.

Unfortunately, photoprint is still a work in progress, and there is
little documentation available.  I managed to build it despite not being
able to find any guidance about to how to do it.  If I remember
correctly, the usual sequence: configure, make, make install
worked, but there may have been some glitches along the way.  After
it is built, how to use it is supposed to be clear from the interface,
but I didn't find it so.  It is probably clear to an expert who is
thoroughly familiar with color management.  But for someone like me who
is still learning, it is a challenge.  I think I now know how to use it,
but it was only by going through the process "manually" with cctiff that
it became clear.  So for those who might be challenged by setting up
photoprint, it might be useful to have an alternative, and that was
partly my reason for bringing this up.

Again, any corrections to what I said would be appreciated.

Leonard Evens <[EMAIL PROTECTED]>
Mathematics Department, Northwestern University

Gimp-user mailing list

Reply via email to