IMAGE ENCODER AND CONTROL METHOD THEREFOR

摘要

PROBLEM TO BE SOLVED: To execute efficient image encoding processing while suppressing memory costs.SOLUTION: An image encoder comprises: a conversion part which generates coefficients of a plurality of sub-bands through wavelet conversion on image data to be encoded; and a predictive encoding part which performs predictive encoding on the coefficients in raster scanning direction for each sub-band. The predictive encoding part comprises: a symbol generation part which finds a prediction value corresponding to a coefficient of interest of a sub-band of interest, and generates a symbol to be encoded from a prediction effort as a difference between the value of the coefficient of interest and the prediction value; an encoding part which performs entropy encoding on the generated symbol using a parameter determined in encoding processing on the coefficient right before the coefficient of interest; an estimation part which estimates a temporary symbol corresponding to a coefficient succeeding the coefficient of interest; and a determination part which determines a parameter for the succeeding coefficient from a code length when the temporary symbol estimated at the estimation part is assumed as being when a parameter used in the encoding of the symbol of the coefficient of interest.SELECTED DRAWING: Figure 6