Recovering planar projections of printed clustered-dot halftones

This paper presents a novel method to recover planar projections (homographies) from perspectively distorted images of clustered-dot halftones. The method uses the variation of the local affine deformation of the halftone (estimated using a Fourier method) to recover the additional projective components. Evidence provided from simulated distortion and mobile capture shows that the approach provides an effective first step in the problem of using mobile device to recover stenographic information embedded in unknown halftone images, as pixel-accurate alignment is needed to recover the data.