Intra encoding and decoding with variable intra prediction direction sets

An apparatus comprising:

• an image decoder to decode an image as a plurality of image regions each having a respective size and the shape;
• and
• an intra-image predictor to predict a current sample of a current region of an image with respect to one or more 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 prediction direction is selected from a set of candidate prediction directions;
• the intra-image predictor being configured to apply two or more different sets of candidate prediction directions in dependence upon an aspect of the image region, the aspect being one of more of:
• the region shape and the position of the region within the image.

A method comprising:

• selecting at least one of the size and the shape of each image region of a plurality of image regions of an image;
• encoding the image as the plurality of image regions;
• and
• intra-image predicting a current sample of a current region of the image with respect to one or more reference samples of the same image according to a prediction direction between the current sample and a reference position amongst the reference samples, the predicting step comprising:
• applying two or more different sets of candidate prediction directions to a given image region in dependence upon an aspect of the given image region, the aspect being one of more of:
• the region shape and the position of the given image region within the image;
• and
• selecting the prediction direction for a sample in the given image region from the set of the candidate prediction directions applicable to that image region.

A method comprising:

• decoding an image as a plurality of image regions each having a respective size and shape;
• and
• intra-image predicting a current sample of a current region of the image with respect to one or more reference samples of the same image according to a prediction direction between the current sample and a reference position amongst the reference samples, the predicting step comprising:
• applying two or more different sets of candidate prediction directions to a given image region in dependence upon an aspect of the given image region, the aspect being one of more of:
• the region shape and the position of the given image region within the image;
• and
• selecting the prediction direction for a sample in the given image region from the set of the candidate prediction directions applicable to that image region