Bias Characteristics of Bilinear Interpolation Based Registration

Image registration has application in many image processing tasks. A new gradient-based registration method that uses the bilinear interpolation equation to predict the pixel values of one image from those in a reference image is developed and its bias characteristics analysed. For sinusoidal signals and step edges, the estimated offset is biased towards the nearest reference pixel, however for noise signals, the bias is away from the nearest pixel. Therefore the bias (and registration accuracy) can actually improve with the addition of noise. This phenomenon is demonstrated with two sample images with quite different image statistics.