An image encoding apparatus comprising: a controller (343, 3210) configured to select, from a set of prediction directions, a set of candidate prediction directions as a subset of the set of prediction directions, for a current image region of a current image in dependence upon one or more properties of a group of reference samples of the current image applicable to the current image region, wherein the one or more properties of the group of reference samples represent at least availability of reference samples for prediction of the current image region; and an intra-image predictor configured to predict samples of the current image region with respect to one or more of the group of reference samples of the same image according to a prediction direction between the current sample and a reference position amongst the reference samples; in which the intra-image predictor is configured to select the prediction direction for the current image region from the set of candidate prediction directions; and in which the controller is configured to supplement the set of candidate prediction directions with one or more additional prediction directions not forming part of the set of prediction directions, the one or more additional prediction directions being allocated additional mode numbers by a mode number mapper by mappings from original modes corresponding to first prediction directions of the set of prediction directions that are not used; wherein the one or more additional prediction directions comprise a prediction direction lying between a respective pair of prediction directions in the set of candidate prediction directions. a controller (343, 3210) configured to select, from a set of prediction directions, a set of candidate prediction directions as a subset of the set of prediction directions, for a current image region of a current image in dependence upon one or more properties of a group of reference samples of the current image applicable to the current image region, wherein the one or more properties of the group of reference samples represent at least availability of reference samples for prediction of the current image region; and an intra-image predictor configured to predict samples of the current image region with respect to one or more of the group of reference samples of the same image according to a prediction direction between the current sample and a reference position amongst the reference samples; in which the intra-image predictor is configured to select the prediction direction for the current image region from the set of candidate prediction directions; and in which the controller is configured to supplement the set of candidate prediction directions with one or more additional prediction directions not forming part of the set of prediction directions, the one or more additional prediction directions being allocated additional mode numbers by a mode number mapper by mappings from original modes corresponding to first prediction directions of the set of prediction directions that are not used; wherein the one or more additional prediction directions comprise a prediction direction lying between a respective pair of prediction directions in the set of candidate prediction directions.