This research emphasis on problem of quantization process in transform-based image compression. In specifying the quantizer, the size of interval is giving huge impact to the quantization performance. Generally, high quantization error will occurred if large interval is used at high difference value bin. Thus, quantizer needs to be design carefully to outfit the value as efficient as possible to reduce the quantization error. Contrary to the traditional approach, that apply uniform or

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... m quantization step size, the proposed one utilize the high occurrence of zero coefficient by re-allocate the non-zero coefficient in a group for quantization. Then the proposed coder employ quantization error minimization mechanism by calculating the difference median quantization error at each quantization interval class. The results are then compared to the standard transform based algorithm and we found that the proposed algorithm compress the image effectively without harming the quality of the compressed image. Keywords-quantization; median error difference, wavelet coefficients I.