I have an image in which the intensity of Red decreases from left to right (similar to the image below). Is it possible for me to compare the intensity of red at two different points?

I need to the values of the intensities of red at equally spaced distances for a science project.In the above picture, is it possible to generate a set of intensity values at every section marked by a thin line? (NOTE: by intensity, I mean the percentage of Red at the point in the image. I would say the intensity is high if the percentage of red is 98% & very low if percentage of red is say 1%)
Is there a script that I can use (in Gimp for example) or can anyone tell me how I can create my own using Python or Scilab? Other tools and languages are also welcome but these two are the ones I'm familiar with.
Thanks. Please comment if my question is not clear enough. I'll try to improve it based on your comments.