1. An image registration method for registering a target image with a reference image, comprising: determining a target set of features present in the target image; determining a reference set of features present in the reference image; generating respective signatures for each feature in the target and reference sets; matching features from the target set to corresponding features in the reference set using the signatures; generating respective transformations to map pairs of features in the target set to corresponding pairs of features in the reference set; and determining a global transformation for the target image using a measure of the accuracy of the transformations, wherein determining target and reference sets of features includes determining regions with similar colors in the target and reference images and clustering such regions, each cluster representing a feature centered on the cluster, wherein the center is described by both its color and position.