Re: Titanic 3D images

[P3D John Ohrt <johrt@xxxxxxx>]

P3D Paul Talbot wrote:
> 
> Re: John Ohrt suggests using 100% setting to achieve lossless JPEG.
> 
> This is not at all true, according to the JPEG FAQ!  In deference to
> the list charter, I won't post  the details here, but anyone who is
> interested in more information can contact me off list.


First, my thanks for being so tactful.

What the FAQ says is not true, but then what I said may not be true.

I assumed that since the only jpeg compressor I use produces a lossless
compressed file with a quality setting of 100, that all others do.

I have used PmView, an OS/2 app that is a great general purpose veiwer
and contains a very capable and very, very fast JPEG encoder.  I haven't
encountered a better encoder yet.

The FAQ on the otherhand suggests that anyone using a quality setting of
100% doesn't know what they are doing.  They are wrong.  Since there is
virtually no reason to use a quality setting above 95 for lossy
compression (the FAQ and I agree here), I think PmView's implementation
of interpretting 100% as an instruction for lossless compression very
intuitive.

To bad the development group didn't have the foresite to specifiy it.
:-)

However, the FAQ and I also agree that with the availability of PNG,
lossless JPEG compression is of little value because PNG has superior
loseless compression algolrithms.

In closing, find out what your JPEG encoder actually does by reading the
documentation and then testing it.  Most implementations are truly
garbage.  A big hint is if it doesn't offer maximum entropy encoding, it
is garbage.  Maximum entropy encoding generates the smallest possible
file, exactly what you want on a web site.

regards, 
--
John Ohrt,  Regina, SK, Canada
johrt@xxxxxxx


------------------------------

End of PHOTO-3D Digest 2019
***************************
***************************
 Trouble? Send e-mail to 
 wier@xxxxxxxxxxxxxxx 
 To unsubscribe select one of the following,
 place it in the BODY of a message and send it to:
 listserv@xxxxxxxxxxxxxxx 
   unsubscribe photo-3d
   unsubscribe sell-3d
   unsubscribe mc68hc11
   unsubscribe overland-trails
   unsubscribe icom
 ***************************