Color detection on GIF or PNG image

Question

We were wondering if it was possible to do something like the attached pictures.

We have a live weather radar on our website, projected on a google maps page with an

Answer 1

I would isolated the red cells by using the -fx operator.

convert source.png -fx '(p.r > p.b && p.r > 0.9) ? p : 0' a_RED.png

The p.r > p.b remove white colors, and the p.r > 0.9 checks the current pixel against a threshold of 0.9.

This approach requires some extra CPU time, but does give you the ability to adjust the degree of severity.