IMAGE CODER AND IMAGE DECODER

摘要

PURPOSE: To obtain the image coder in which image quality is improved by eliminating block noise caused by image compression coding. CONSTITUTION: A transforming unit 31 divides a digital image signal into plural image blocks and discrete wavelet transformation conducting plural stages of band division is applied to each image block. A predictive arithmetic section 32 predicts conversion data of an image block for a high frequency band after the discrete wavelet transformation from transformed data at an optional frequency band obtained by the discrete wavelet transformation processing by the transforming unit 31, and a difference between the prediction result and the transformed data for the high frequency band obtained by the discrete wavelet transformation by the transforming unit 31 is taken. Coding means 33, 34 apply compression coding to transformed data at an optional frequency band obtained by the transforming unit 31 and applies compression coding to the result of subtraction obtained by the prediction arithmetic section 32 as transformed data at a high frequency band.