Flame intensity at every pixel of an image

I am working on a project in which I have to predict flame temperature using a non-contact technique (two color method).

Can you please help me on how to find flame intensity at every pixel of the image?

Here is the link of flame image: https://drive.google.com/file/d/0Byy8GCAG9WQcRUtTb1hhNU51Q3M/edit?usp=sharing

Thanks!