1. A method of classifying an image comprising: generating, in a device configured to process images, features based at least in part on a block frequency domain representation of said image, wherein at least one of said features is based at least in part on a prediction error image, wherein generating the features includes transforming the prediction error image and applying a histogram operation to a result of the transforming of the prediction error image; and classifying said image based at least in part on said generated features.