I think I got it.  But it seems the center is quite empty but it seens better than mmcdara edge concentration which appears to be concentrated in a pole like manner.  So for this I just changed the x1 and y1 to 1/4 powers to concentrate more towards the edge boundary evenly.

@mmcdara hey that's pretty neat. 

The plot of concentration near the boundary plot is more concentrated near left and right points on the edge. 

How would you modify it so the concentration is more towards the outside edge?

@mmcdara Thanks for you points and links.  It was only a very general case, and not time dependent, basically a blanket generalization - as t approaches infintiy the total number of people sick is 30%.  As you mention we could include many time dependencies such as but not limited to, time of exposure, time of incubation, time sick but not infectious, time not sick but infectious etc..

It would be interesting to see someone come up with a model like you describe, actually I came across this 2D covid visualization simulation which would make a great maple application https://pongcenter.itch.io/anti-plague linked from this article https://www.frontiersin.org/articles/10.3389/fcomp.2021.642321/full#SM1 (Simulation Agent-Based Model to Demonstrate the Transmission of COVID-19 and Effectiveness of Different Public Health Strategies)

In the meantime I'll check out the links you mention, I've got a bit of reading to do.

@Carl Love  Great! Thanks that's it.

Mapleflow ends with = and it automatically enters 1.  One of the minor differences from Maple.

Very insightful, thanks all.

@ccAndrew actually I did locate a 2016 answer.  I would like to be able to cycle through his posts, but I cannot since his user account in mapleprimes doesn't appear to be working.

@Valerie I'm not sure if I'm getting the right output.  Can you show your input and output signals here?  I would also, if possible, like to see a visual simulation of the box and mass.

Masking is I suppose not the correct term.  More or less a notch filter I think is what it is. 

In the clown example the trouble is how to get this but I think what has been left out was that it was loaded in an editor (paint) and red circles were manually applied and saved as a seperate file, loaded back in and from there extracted a difference image against the unedited version.  

What I found on the web was this

Please present a reference

Regarding the screen angle I think it has something to do with gamma correction.  I don't know if that has anything to do with blocking certain colors but if I tilt the screen, more and more red is blocked and we see more green and blue, at least on some monitors.  I think I can simulate the colors I see be reducing the red channel in the image.  The gamma correction controls the brightness so maybe yes changing the brightness of the color channel is in effect changing the gamma.

With my laptop as the lid is closed the colors at a steep angle change (white becomes black, light greys stay white etc..)  I am trying to replicate the colors you see when you look at a steep angle on a screen.

The windows logo looks slightly different on an angle and I thought it was a color inversion or negative.  Is there any way to replicate those steep angle colors?

@acer I didn't know a color inversion was the same thing as a negative, but that makes sense. 

There is an illusion in the windows logo which I am trying to replicate.

How about an image negative?

@Acer Yes, I think.  I also found these other two ways that do the same thing

Using the windows 7 background desktop as the image

with(ImageTools):

img:=Read("c:/Windows/Web/Wallpaper/Windows/img0.jpg):
img1:=evalf(map(x->(1-x),img)):View(img1)

I also found another way to display the same thing

img2:=FitIntensity(img,1..0):
View(img2)