The disclosure relates to an image processing system of encoding spectral coefficients of an image. According to the disclosure, the spectral coefficients of the image are received, the spectral coefficients being quantized, and a scaling factor to be applied to the image for rendering a bitmap of the image after decoding is received. The received spectral coefficients are partitioned into a plurality of groupings, wherein a number of coefficients in each of the groupings is determined based on the scaling factor for rendering the bitmap of the image. The spectral coefficients in each of the plurality of groupings are encoded, and the plurality of groupings of encoded spectral coefficients are transmitted to a decoder.