Possible bug when drawing in composite images?

Posted by Peter van Loon on Apr 22, 2015; 8:01am
URL: http://imagej.273.s1.nabble.com/Possible-bug-when-drawing-in-composite-images-tp5012564.html

Hi,
I found a strange behavior when drawing in composite images in combination with an adapted gray LUT.

Situation:
I like to make some manual corrections in several layers of a composite image. The first 3 layers contain the RGB channels of the image. The fourth channel contains a binary mask. This mask is used to manual edit the areas to be measured. I linked this channel to an adapted Grays LUT. Index 255 is set to the color 255,0,255 (Magenta).
When I use the Paintbrush tool and set the Foreground color to white (255), the painted area has the value 254 instead of 255! This happens when the picture is in composite or color mode (Channels tool). However when I change to Grayscale mode (channels tool) once and go back to composite or color mode. The next edits have the value 255. It looks like a bug? My workaround is now to change for a moment to the grayscale mode and go back to composite and start drawing then. Maybe there are better solutions?

I attached the lut file: Gray_Magenta.lut

Regards,
Peter