That Truck Again

[P3D Dylan The Hippy Wabbit <spacey@xxxxxxxxxxxxx>]

Hi Folks,

John Gross said:-

>I agreed that high resolution JPEG images with 0% compression
>might yield good quality.  If  you don't compress the images with JPEG,
>then why use it;  there are image compression techniques which will
>provide compression without any loss of quality.

Actually 0% compression is a bit of a misnomer.  Considerable compression
is achieved on the minimal setting, some of it lossy.  You can actually
tweak the setting a bit higher than that and get quite a lot more
compression for invisible loss of data.  Just choose the setting that
suits your taste and budget.  If you want the techie details there is a
JPEG FAQ out there somewhere.

>On the other hand, lossy compression techniques, such as JPEG and JPS,
>when they don^Rt find enough redundancy in an image,  blur the colors to
>create some.  Apply the name list metaphor to JPEG, and Jonathan Gross
>and Larry Berlin might come out John Grossman and Lance Berman.  Close
>enough?

That's not a very good comparison.  We are very intolerant of variations
in spelling.  Well, mostly.  That's why we use lossless compression on
text files.  However, I defy you to spot the difference between #F0F0F0
and #F0F0F1.  Especially if they are fluctuating at a high frequency
between those values.  (For those not used to referring to colours as
hexadecimal numbers that's grey and grey with a *very* faint touch of
blue.)

JPEG was very carefully designed to lose only data that your eye/brain
combination will lose anyway.  At least at moderate compression settings.

It will have to do until server storage, bandwidth and high res high
refresh monitors become more affordable.  Then we can still use JPEG to
send *even larger* pictures around.

So!  Are you, or any one else, up for a blind testing?  What I propose is
that I scan one of my pairs at a moderate resolution, something you can
probably display side by side on most monitors.  (400 pixels wide
perhaps?)  Then I save it at varying compression ratios, all from the
original.  No decompression/recompression artifacts thank you.  With some
monkeying around I should be able to disguise the varying file lengths and
creation times.  Then any one interested can try to sort them in order
without being told the compression settings.

Just a couple of questions.  Would separate left and right images be
preferred or a cross-eyed JPS?  Also, I don't know too much stats, so
perhaps some one could advise me on an easy way to handle the results.  I
was thinking in terms of a goodness of fit test.

Dave

______________________________________________________________________________

When you break rules break 'em good and hard.   - Terry Pratchett


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