Re: COlor Picker seems odd at highest and lowest values in gradient section

Posted by Wayne Rasband-2 on Sep 01, 2020; 8:29pm
URL: http://imagej.273.s1.nabble.com/COlor-Picker-seems-odd-at-highest-and-lowest-values-in-gradient-section-tp5023896p5023906.html

> On Aug 31, 2020, at 9:45 AM, Bill Christens-Barry <[hidden email]> wrote:
>
> Hi,
>
> I've noticed what I think is a changed behavior of the Color Picker concerning its leftmost section that displays as a grayscale gradient. In that section, low values are displayed as dark at the top and high values displayed as light at the bottom.
>
> In macOS 10.14.6 (Mojave), to pick the lowest value (0) you must pick just beneath the highest value in the gradient. The lowest value that can be picked at the top of the gradient is not 0 but is 1.

I am not able to reproduce this problem but the Color Picker in the ImageJ 1.53e12 daily build adds a 2 pixel high row of black pixels at the top of the canvas that makes it easier to pick black. You can also click on the “reset” icon in the lower right corner to set foreground to white and background to black.

-wayne

> This behavior also holds for different image types and how their values are displayed numerically. Moreover, if you click in the regions above or beneath the gradient near its lowest or highest values, the lowest non-zero value (1) or the highest value (255), respectively, is selected.
>
> This seems counterintuitive; would it be better to have the lowest value be at the top of the gradient region? I wonder if this might be a regression, perhaps due to a non-zero based 8-bit index rollover (255 + 1 = 0).
>
> On Windows 10 this behavior is slightly different.
>
> Bill

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