Similarity invariant energy minimising deformation for iOS
by Shizuo Kaji
Multi-touch on the image to deform. Look at the following paper for theoretical background.
 S.Kaji, S.Hirose, S.Sakata, Y.Mizoguchi, and K.Anjyo, Mathematical Analysis on Affine Maps for 2D Shape Interpolation, Proceedings of SCA2012 (ACM SIGGRAPH/Eurographics Symposium on Computer Animation 2012), pp. 71--76.