Posted by
Jeremy Adler on
Mar 24, 2016; 11:05am
URL: http://imagej.273.s1.nabble.com/Re-jpeg-artifacts-the-Glasbey-LUT-tp5016000.html
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_imagingRegards,
Curtis
--
Curtis Rueden
LOCI software architect -
http://loci.wisc.edu/softwareImageJ2 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
>
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http://imagej.nih.gov/ij/list.html>
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