Methods and Systems for Image Intra-Prediction Mode Management

An image decoding system for decoding a digital image comprising:

• a) means for decoding each of blocks into which an image is divided;
• b) intra-prediction means for predicting values of pixels located along a specified direction in a target block to be decoded by using a same prediction value;
• and
• c) prediction mode estimating means for estimating a prediction mode for the target block;
• wherein the intra-prediction means uses a prediction value being a weighted average of plural pixels located adjacent to the target block as a prediction value of the target block,
• d) the prediction mode includes a Diagonal Down/Left prediction mode using the specified direction being diagonally downward to the left at approximately a 45 degree angle, a Diagonal Down/Right prediction mode using the specified direction being diagonally downward to the right at approximately a 45 degree angle and an intermediate angle prediction mode using the specified direction being diagonally at approximately a 22.5 degree angle or a 67.5 degree angle,
• e) the prediction modes are numbered with increasingly larger numbers, in order of the Diagonal Down/Left prediction mode, the Diagonal Down/Right prediction mode and the intermediate angle prediction mode, and the prediction mode estimating means determines a prediction mode to have the lower mode number among the prediction mode of a first block located adjacent to and above the target block and the prediction mode of a second block located adjacent to the left side of the target block as the prediction mode for the target block.

A prediction method for predicting a pixel value of each of blocks into which an image is divided in an image processing device for encoding or decoding a digital image comprising;

• a) an intra-prediction step of predicting values of pixels located along a specified direction in a target block to be predicted by using a same prediction value;
• and
• b) a prediction mode estimating step of estimating a prediction mode for the target block;
• wherein
• c) the intra-prediction step uses a prediction value being a weighted average of plural pixels located adjacent to the target block as a prediction value of the target block,
• d) the prediction mode includes a Diagonal Down/Left prediction mode using the specified direction being diagonally downward to the left at approximately a 45 degree angle, a Diagonal Down/Right prediction mode using the specified direction being diagonally downward to the right at approximately a 45 degree angle and an intermediate angle prediction mode using the specified direction being diagonally at approximately a 22.5 degree angle or a 67.5 degree angle,
• e) the prediction modes are numbered with increasingly larger numbers, in order of the Diagonal Down/Left prediction mode, the Diagonal Down/Right prediction mode and the intermediate angle prediction mode, and the prediction mode estimating step determines a prediction mode to have the lower mode number among the prediction mode of a first block located adjacent to and above the target block and the prediction mode of a second block located adjacent to the left side of the target block as the prediction mode for the target block.