Re: jpeg artifacts, the Glasbey LUT

Posted by ctrueden on Mar 24, 2016; 12:10pm
URL: http://imagej.273.s1.nabble.com/Re-jpeg-artifacts-the-Glasbey-LUT-tp5016000p5016002.html

Hi Jeremy,

The glasbey LUT is included with Fiji.

See also http://imagej.net/Glasbey

I also posted my macro to http://imagej.net/Principles in the JPEG section;
if you want to eliminate the dependency on glasbey then by all means: edit
away.

Regards,
Curtis
On Mar 24, 2016 6:17 AM, "Jeremy Adler" <[hidden email]> wrote:

> Hej Curtis,
>
> Your macro does the job but I am confused by the reference to the glasbey
> LUT
>
> My version of FIJI (1.50h) has a glasbey inverted LUT, it this what you
> meant or is there a glasbey LUT somewhere else ?
>
> When I look at the glasbey inverted LUT with a 256 step greyscale ramp -
> it seems to have no obvious structure. What is its purpose ?
> If the intention is to highlight the small differences in pixel values
> between the original and jpegged image then Image Adjust/Brightness &
> Contrast would do the job especially when combined with the 16 colors LUT
>
>
> -----Original Message-----
> From: ImageJ Interest Group [mailto:[hidden email]] On Behalf Of
> Curtis Rueden
> Sent: den 23 mars 2016 20:41
> To: [hidden email]
> Subject: Re: jpeg artifacts
>
> Hi John,
>
> > can someone supply a definitive, reproducible example that I and my
> > team can use as a test case?
>
> Here is a macro which demonstrates the issue:
>
> ----------
> // load Boats
> run("Boats (356K)");
> run("Out [-]");
> rename("Original");
>
> // convert to JPEG
> run("Duplicate...", " ");
> run("Out [-]");
> run("Save As JPEG... [j]", "jpeg=85");
> run("Revert");
> rename("JPEG");
>
> // compute the difference
> imageCalculator("Subtract create 32-bit", "Original","JPEG"); run("Out
> [-]"); rename("Difference");
>
> // display windows side by side
> run("Tile");
>
> // highlight artifacts using Glasbey LUT selectWindow("Original");
> run("glasbey"); selectWindow("JPEG"); run("glasbey");
> selectWindow("Difference");
> ----------
>
> See also
>
> http://imagej.net/Principles#Why_.28lossy.29_JPEGs_should_not_be_used_in_imaging
>
> Regards,
> Curtis
>
> --
> Curtis Rueden
> LOCI software architect - http://loci.wisc.edu/software
> ImageJ2 lead, Fiji maintainer - http://imagej.net/User:Rueden Did you
> know ImageJ has a forum? http://forum.imagej.net/
>
>
> On Wed, Mar 23, 2016 at 1:30 PM, John Brear <
> [hidden email]> wrote:
>
> > 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
> >
>
> --
> ImageJ mailing list: http://imagej.nih.gov/ij/list.html
>
> --
> ImageJ mailing list: http://imagej.nih.gov/ij/list.html
>

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