Posted by
Herbie on
Mar 24, 2016; 10:46am
URL: http://imagej.273.s1.nabble.com/jpeg-artifacts-tp5015994p5015999.html
John,
apart from the clearcut visualizations by Curtis and Michael I'm puzzled
by your question:
"Is this advice still current?"
JPEG is a _lossy_ compression technique that was standardized back in
1992/94 (ISO/IEC 10918-1:1994):
<
http://www.iso.org/iso/iso_catalogue/catalogue_tc/catalogue_detail.htm?csnumber=18902>
Why do you think things have changed since?
A standard is a standard, is a standard, ...
PNG is a nice alternative (standardized in 2004) for _lossless_ compression.
<
https://en.wikipedia.org/wiki/Portable_Network_Graphics>
In general lossy compression is unsuited for scientific image processing
and analyses. And please keep in mind that processing JPEG images and
again compressing them as JPEGs gives rise to further artifacts (for
exceptions see <
https://en.wikipedia.org/wiki/JPEG>)!
Best
Herbie
::::::::::::::::::::::::::::::::::::::::
Am 23.03.16 um 19:30 schrieb John Brear:
> Hi, I am relatively new to ImageJ - investigating its suitability for
> quantitative metallography, particularly precipitate particle
> characterisation. My apologies, therefore, if I am treading on
> well-worn ground.
>
> In the user guide I see strong warnings against using jpeg images,
> see 'Noteworthy II, X'. However, I cannot reproduce the effects
> described, neither using the exmple image of the mandril/baboon
> (which is supplied as a jpeg anyway??), nor using my own images. I
> have tried comparing bmp, jpg, tif, gif, png.
>
> Is this advice still current? If so, can someone supply a definitive,
> reproducible example that I and my team can use as a test case?
>
> Thanks in anticipation, Best wishes, John
>
> -- ImageJ mailing list:
http://imagej.nih.gov/ij/list.html>
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