[argyllcms] Determining proper error value for -r
- From: Ben Goren <ben@xxxxxxxxxxxxxxxx>
- To: argyllcms@xxxxxxxxxxxxx
- Date: Tue, 23 May 2006 07:16:14 -0700
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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