Re: Possible bug when drawing in composite images?

Posted by Rasband, Wayne (NIH/NIMH) [E] on Apr 23, 2015; 3:42am
URL: http://imagej.273.s1.nabble.com/Possible-bug-when-drawing-in-composite-images-tp5012564p5012576.html

On Apr 22, 2015, at 4:01 AM, Peter van Loon <[hidden email]> wrote:

>
> 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?

Set the foreground color to magenta (255,0,255) and the paintbrush tool will work as expected with your gray_magenta LUT. A magenta foreground color matches the magenta entry in the LUT, which has an index of 255. A white foreground color (255,255,255) matches the whitest entry in the LUT, which has an index of 254.

-wayne


> I attached the lut file:  Gray_Magenta.lut
> <http://imagej.1557.x6.nabble.com/file/n5012564/Gray_Magenta.lut>  
>
> Regards,
> Peter
>
> --
> View this message in context: http://imagej.1557.x6.nabble.com/Possible-bug-when-drawing-in-composite-images-tp5012564.html
> Sent from the ImageJ mailing list archive at Nabble.com.

--
ImageJ mailing list: http://imagej.nih.gov/ij/list.html