Re: information about LUTs and image manipulation

Posted by Wayne Rasband on Jan 10, 2008; 8:55pm
URL: http://imagej.273.s1.nabble.com/information-about-LUTs-and-image-manipulation-tp3697616p3697617.html

> Hi Imagers,
>     In my work with brain images, I convert from a 256-gray LUT to a
> 16-gray LUT. The graphic display of the new LUT works fine.
>
> When I save the 16 gray'ed image and reopen the recently-saved 16 gray
> level image, the display uses 16 levels but the value of each pixel
> corresponds to a value in a 256 gray LUT. That is, the values of the
> pixels in the 16 level image are one of 255.
>
>  What does it take to save the values of the pixels in the displayed
> 16 gray level image as one of 16 values?

One way to do this is to convert the image to RGB using Image>Type>RGB
Color and then convert it back to grayscale using Image>Type>8-bit. You
can create a 16 gray LUT by clicking on "Set" in the Image>Color>Edit
LUT window and entering 16 as the "Number of Colors" and selecting
"Replication" for 'Scale Using".

-wayne