PYTHON: How to scale color channels of an imported image to find the area fraction within certain indices (see below)?

Question

Question 1.2: Scale the red channel by 150 C, the green channel by 90 C, and the blue channel by 40 C. Add the contribution of each channel to compute the resulting temperature. Calculate the area fraction with temperature between 220 C and 240 C and indicate the area on a plot of the array as follows.

Answer 1

For each pixel....

I am GUESSING that the normalizing is:

(Red-150)/255

(Green-90)/255

(Blue-40)/255

assuming they are sufficient

You then plug them into your formula to get the temperature

If it is in the range increment the counter

You can get the percentage in that range by dividing the count by the # of pixels