Patent ID: 7676097

Claim:
A digital image encoding device which encodes digital image data using a discrete wavelet transform, the digital image encoding device comprising: a coefficient bit shift processing unit that performs bit shift processing on a wavelet coefficient after the discrete wavelet transform, wherein the coefficient bit shift processing shifts the wavelet coefficient to a lower bit side by a predetermined number of bits to truncate the predetermined number of bits on the lower bit side of the wavelet coefficient, replaces the predetermined number of bits on an upper bit side of the wavelet coefficient with zeros, and reduces a number of effective bits to create a new wavelet coefficient and wherein the coefficient bit shift processing unit calculates degrees of contribution of image quality for each sub-band coefficient constituting the wavelet coefficient, and performs different bit shift processing for each sub-band coefficient according to the degrees of contribution by using a bit shift of one bit for a sub-band of a luminance component of the digital image data and a bit shift of more than three bits for a color difference component of the digital image data.