P3D Re: JPG and destruction

[jacob@xxxxxxxxxxxxxx (Gabriel Jacob)]

Boris Starosta writes,
>My turn!

Well it's about time! Now it's mine. ;-)

>Ole's ad hominem attack on the Chinese aside, I can comment only on my
>personal subjective experiences with JPEG, which have been both very good
>(as far as image quality goes), and very bad (as far as getting others to
>accept the high quality of such files).  People seem to be biased against
>JPEG.

Not me! I love jpeg and most on this list, I think do also. There has
been some arguements trying to explain why jpeg is detrimental to 3-D,
but I still don't buy it. First of all, the proof is in the puddding.

What I have noticed is that, whatever algorithm the specific software
is using, it doesn't degrade stereo-pairs at low compression settings.
I think anyone would be hard pressed to see any degradation of a jpeg
stereo-pair vs. a non-lossy stereo-pair such as a bmp. As for anaglyphs
that is another matter, see below.

Jon Siragusa writes,
>Also remember that all JPEG compressors are not created equal!
>We have found that quality and file size vary from compressor
>to compressor.  Try out a few different programs and see which
>ones give you the best results at the highest quality setting. 
  
And Tom Deering writes,
>There is no one single JPEG compression. There is a standard
>set of rules, with some optional parts. The JPEG standard does not
>specify exactly how the compressing or decompressing software will
>behave. The programmer can choose a fast-but-less-acurate algorithm,
>or a slower-but-more-accurate algorithm.  This is true for
>compressing and decompressing.  There is a big difference in JPEGing
>software.

Thank you both gentlemen! That has always been my suspicion. I have
noticed that different JPEG compressors have a big effect on a 
anagyph image. The less efficient compressors leaving all kinds of
artifacts in the image even at the lowest compression setting.
I have tried a few but wasn't too happy with them.

Boris writes,
>The images on my site, including anaglyphs, are also all JPEGs
>(www.starosta.com/3dshowcase), saved generally as medium quality, medium
>compression files.  When I save at high quality, which can still give a
>compression ratio of close to 10:1, it impossible to detect JPEG artifacts
>without significant enlargement of the image.

Very true. I noticed your jpeg anaglyphs were of very good quality.
(I do take issue with the stereo window, but that is another matter.)  

Another good point as Boris points out is if the anaglyph image is made
with digital cameras that use jpeg files. This complicates matters and
no matter how good the compressor is, the image won't be opitimal.

Gabriel


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

End of PHOTO-3D Digest 2690
***************************