Image signal coding and decoding method.

摘要

In an image signal coding and decoding method in which feature points in an image signal are detected and information concerned with sets of continuous feature points is chain-coded, the quantity of information is reduced without deterioration of image quality. In the image signal coding and decoding method, components of a direction displacement between the direction of transition from a feature point two feature points before a current feature point to a preceding feature point and the direction of transition from the preceding feature point to the current feature point are detected and subjected to entropy coding. By this method, coding can be performed which uses stochastic correlation between the direction of transition from the feature point two feature points before the current feature point to the preceding feature point and the direction of transition from the preceding feature point to the current feature, so that the number of direction codes expressing the positions of respective feature points can be reduced, and therefore the quantity of information can be reduced.