IMAGE ENCODING AND DECODING APPARATUSES, IMAGE ENCODING AND DECODING METHODS, PROGRAMS THEREOF, AND RECORDING MEDIA RECORDED WITH THE PROGRAMS

摘要

A method for encoding an image using an intra-screen prediction comprises a step of selecting, from a plurality of gradient candidates, a gradient of pixel values indicated by an image signal to be predicted. Based on the gradient, a gradient is given according to the distance from a predicted reference pixel to generate a prediction signal. Based on the prediction signal, intra-screen encoding is performed on the image signal to be predicted and the information indicating the magnitude of the selected gradient is encoded. Alternatively, based on the already encoded image signal, a gradient of the pixel values indicated by the image signal to be predicted is estimated. Based on this gradient, a gradient is then given according to the distance from the predicted reference pixel to generate a prediction signal and based on this prediction signal, intra-screen encoding is performed on the image signal to be predicted.