IMAGE PROCESSING APPARATUS AND METHOD, AND STORAGE MEDIUM

A discrete wavelet transformer computes the discrete wavelet transform of an input X-ray image, a quantizer quantizes coefficient values corresponding to a region of interest of the transformed coefficients as values relatively larger than coefficients corresponding to a non-region-of-interest, and an entropy encoder generates a code sequence by encoding the quantized coefficient values. The region of interest is extracted in such a manner that an irradiation region extraction unit detects an irradiation field region of X-rays of the input X-ray image, detects a through region by computing the histogram of pixel values of that irradiation field region, and removes the through region from the irradiation field region.