REDUCTION OF BLOCKING ARTIFACT IN BLOCK-CODED IMAGES USING WAVELET TRANSFORM

We propose a simple yet efficient method which reduces the blocking ar tifact in block-coded images by using a wavelet transform. An image is considered a set of one-dimensional signals, and so all processings i ncluding the wavelet transform are one-dimensionally executed. The art ifact reduction operation is applied to only the neighborhood of each block boundary in the wavelet transform at the first and second scales . The key idea behind the method is to remove the blocking component w hich reveals stepwise discontinuities at block boundaries. Each block boundary is classified into one of shade region, smooth edge region, a nd step edge region. Threshold values for the classification are selec ted adaptively according to each coded image. The performance is evalu ated for 512 x 512 images JPEG coded with 30:1 and 40:1 compression ra tios. Experimental results show that the proposed method yields not on ly a PSNR improvement of about 0.69-1.06 dB, but also subjective quali ty nearly free of the blocking artifact and edge blur.