Camera Calibration using Single Input Image
Take a look at this paper here: "Straight lines have to be straight" by Faugeras et al.
http://link.springer.com/article/10.1007/PL00013269#page-1

It is straight forward to implement, but essentially removes distortions by observing the straightness of lines.

It should be straight forward to implement if you remove some automation (e.g. you click on the lines manually rather than relying on image processing).