How to calculate and compare density of smoke and fog in an image?

I want to calculate and compare density of smoke and fog in an image using matlab. It would be of great help if you could provide some ideas and tutorials on the same.

[Rik]

Have a read here and here. It will greatly improve your chances of getting an answer.

Try something out, and if you have trouble with your code, come back with a specific problem. Showing some example inputs and desired output helps.