In my class I often need to work with color map images. I would show the image and try to make inferences/observations about different subjects. Often times I need to actually quantify some aspects, but it is always very approximate and somehow vague because the images are provided "as is" and I do not necessarily know their content a priori.
Let's imagine I'm working with two images (*). I would love to tell my computer to "learn" the color scale bar so I can click at any point in the map to get the value of altitude at that point? Image 1 is a discrete color scale bar, while Image 2 has a continuous color mapping. I included both examples because maybe there are differences in the approach of how to do this.
So, is there a software/way to do this? Preferably open source. I tried ImageJ and couldn't come up with a decent solution.
(*) Image 2: http://topocreator.com/ned-jpg/city_a/600/co.jpg
(*) I do not own any of these images, just examples I found online to illustrate my point.