Image encoding device and decoding device, image encoding method and decoding method, program for the devices and the methods, and recording medium recording program

Abstract

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.

Description

technical field [0001] The present invention relates to an image encoding device and its method for encoding an image using intraframe prediction, an image decoding device for decoding encoded data encoded by the image encoding technique and its method, for realizing the image encoding device An image encoding program and a computer-readable recording medium recording the program, an image decoding program for realizing the image decoding device, and a computer-readable recording medium recording the program. [0002] This application claims priority based on Japanese Patent Application Japanese Patent Application No. 2007-267614 for which it applied on October 15, 2007, and uses the content here. Background technique [0003] Intra predictive coding in which prediction is performed within the same frame cannot achieve as high a compression efficiency as inter predictive coding in which prediction is performed between different frames, so an intra predictive coding method wi...

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Problems solved by technology

[0022] Therefore, according to the existing intra prediction, there is a problem that the increase of the residual signal cannot be avoided, and the compression efficiency deteriorates.

[0023] Therefore, in the existing intra prediction, when applied to an image whose value of the original signal varies spatially, that is, an image containing many layers (such an image is common), there is an increase in the residual signal, compression efficiency worsening problem

[0024] On the other hand, the method described in Non-Patent Document 3 uses a method of performing intra prediction based on prediction values ​​when two prediction modes are applied, but this method does not perform prediction using the hierarchical properties of the original signal.

Therefore, it cannot be expected to greatly improve the compression efficiency

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