I don't understand what is your problem / your question.

No problem. I will try to clarify.

1. Objective
Draw a text or something else with a flashlight in front of a webcam

2. The way I tried to do it
User can choose a value (brightLimit) which define the brightness limit. This limit allow to keep only high brightness pixels on the screen (PImage screen).
The code I copied/pasted on last post, compare brightness, pixel by pixel, of last live camera frame and screen image. The new screen image displayed is a superimposition of the brightness pixels. Sorry but it's not easy for me to explain that in english.

3. The problem(s)
In the exemple I posted above (png file), we can see "Clem" drawed with mostly white color and some red too (I used a red LED). I would like to have a clean red circle to draw my text.
Two problems : I've got more white than red (which is not so important for me).
The second problem is more annoying : Sometimes, I don't know why, but the red color is much more larger (you can see that on the "L" of "Clem"). It happens on almost every test I do.

4. The question
How can I do to reduce this effect. How can I try to obtain a superimposition of red circles without these kind of  "color explosion" ?

Hope it's  better for you.