[argyllcms] Determining proper error value for -r

First, it  wouldn't surprise  me in the  slightest if  I'm missing
something  completely obvious,  smoking crack,  or otherwise  just
plain  out  of  my   gourd. Corrections,  suggestions,  etc.,  are
perfectly welcome.

Anyway, it  occurred to  me that  the best way  to figure  out the
proper error value to use for the -r option of profile would be to
print out  a chart  with a  bunch of patches  of the  same colors,
measure it,  and then  figure out what  the standard  deviation is
(and convert  that into a  percentage). So, that's exactly  what I
did: I created  a 39-patch  chart, did  a copy /  paste in  a text
editor (with some editing) to make  eight copies of the patch set,
printed it, measured  it, imported the results  into an OpenOffice
spreadsheet, and fiddled around with it until I came up with about
a third  of one  percent as  the error--which is  in line  with my
eyeball guesses. (I'll be  doing some more testing  later today to
further confirm and explore all this.)

I'm also pretty sure that that value  would be much too low for my
parents' cheap  color laser printer,  and probably a bit  too high
for ``real'' paper  (I did this on plain paper  just to figure out
if it even made sense to  do in the first place). I'm also curious
to learn just how much of an impact patch size has on accuracy.

However,  it  also occurs  to  me  that  this same  process  could
probably be  done better and  easier by Argyll itself,  and here's
how I imagine it working:

There'd be a new flag to  targen, similar to the existing -e flag,
that tells  how many times to  repeat /all/ patches, not  just the
white ones. When profile is fed  a chart with repeated patches, it
calculates the  appropriate value for  -r itself, uses  that, then
creates a  profile and  reports the recommended  value for  -r for
future use. You  can then  use the generated  profile with  the -c
option of targen or just toss it entirely.

So, is  this something that  I can entice somebody  <avoids making
eye  contact with  Graeme but  can't help  looking in  his general
direction> with the requisite C skills into adding to Argyll? Does
it even make sense to do it in the first place?

Cheers,

b&

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