Re: Enhance Contrast with 16 bit images only uses 256 bins

Posted by Rasband, Wayne (NIH/NIMH) [E] on Dec 03, 2010; 9:50pm
URL: http://imagej.273.s1.nabble.com/Enhance-Contrast-with-16-bit-images-only-uses-256-bins-tp3686304p3686305.html

On Dec 2, 2010, at 4:45 AM, Charles Brossollet wrote:

> Hello,
>
> I have problems using contrast enhancement on 16 bit gray-level images. My
> images have 99% of pixel values in the 5% of true min-max range, so an
> histogram with 256 bins will have huge pixel counts on a few bins. This
> gives inappropriate contrast enhancement since it seems that ImageJ uses 256
> bin histogram for this function.
>
> I have an example image here:
> http://dl.dropbox.com/u/2539804/TD1.tif
>
> Good LUT range for this image is about 5 to 250 levels, but the "enhance
> contrast" with 0,35 gives 3 to 743, leading to a poorly contrasted display.
> INMHO computing histogram on more bins should solve the problem

The Process>Enhance Contrast command in the 1.44l daily build uses 65536 bin histograms with 16-bit images.

-wayne