How to measure intensity of each RGB channel in 1 RGB of 1 ROI?

Hi, guys!
With merged rgb image, can I draw 1 ROI (eg. cell shape according to green actin) then measure the intensity of blue and red seperately in this ROI? If so, how can I do it?
Thanks!

Hello Zonghan -

I assume that you start with a single RGB color image (not a
multi-slice stack).

The simplest way is to run Image > Type > RGB Stack
This will give you a three-slice stack, with each slice being
one color channel.

Now draw your ROI on the (first slice of the) the stack. (This
ROI will automatically be used for all slices.)

Run Analyze > Measure while the stack is displaying its
first (red) slice. The “Mean” column of the Results will be the
mean red intensity within the ROI. Now scroll to the second
(green) slice and run Measure again. This will give you the
mean green intensity. Repeating this for the blue slice will
give you the blue intensity.

Thanks, mm