1. A method of image encoding, the method comprising: performing a wavelet transform on all pixel values in a digital image data to obtain transform coefficients; scaling up said transform coefficients corresponding to each region of interest, wherein said scaling up is performed based on a bit shift value; encoding said transform coefficients to obtain a coded digital image data; and forming a bit stream including said coded digital image data and a header including a ROI coordinate information and said bit shift value, said bit shift value being assigned to each region of interest identified by said ROI coordinate information.