This tool includes the guided filter, the guided upsampling, and the residual interpolation.
Please run runall.m in the examples folder.

Reference:
The guided filter:
Kaiming He, Jian Sun, and Xiaoou Tang, Guided Image Filtering, European Conference on Computer Vision (ECCV), 2010.

Kaiming He, Jian Sun, and Xiaoou Tang, Guided Image Filtering, IEEE Trans. Pattern Analysis and Machine Intelligence (TPAMI), Vol. 35, No. 6, pp. 1397-1409, 2013.

The guided upsampling:
Yusuke Monno, Masayuki Tanaka and Masatoshi Okutomi, Multispectral demosaicking using guided filter, Proceedings of IS&T/SPIE Electronic Imaging (EI2012), Digital Photography VIII, Vol.8299, pp.82990O-1-7, January, 2012.

The residual interpolation:
Yusuke Monno, Daisuke, Kiku, SUnao Kikuchi, Masayuki Tanaka and Masatoshi Okutomi, Multispectral Demosaicking with Novel Guide Image Generation and Residual Interpolation, IEEE International Conference on Image Processing (ICIP), 2014.

Daisuke Kiku, Yusuke Monno, Masayuki Tanaka and Masatoshi Okutomi, Residual interpolation for color image demosaicking, IEEE International Conference on Image Processing (ICIP), pp.2304-2308, 2013.

The related web pages:
http://research.microsoft.com/en-us/um/people/kahe/eccv10/
http://www.ok.ctrl.titech.ac.jp/res/MSI/MSI_e.html
http://www.ok.ctrl.titech.ac.jp/res/DM/RI.html