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The Scientific World Journal
Volume 2015, Article ID 821497, 11 pages
http://dx.doi.org/10.1155/2015/821497
Research Article

A Novel Psychovisual Threshold on Large DCT for Image Compression

1Faculty of Information and Communication Technology, Universiti Teknikal Malaysia Melaka, 76100 Melaka, Malaysia
2Faculty of Computer Science, Universitas Dian Nuswantoro, Semarang 50131, Indonesia

Received 21 February 2014; Revised 20 August 2014; Accepted 6 October 2014

Academic Editor: Ahmad T. Azar

Copyright © 2015 Nur Azman Abu and Ferda Ernawan. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

A psychovisual experiment prescribes the quantization values in image compression. The quantization process is used as a threshold of the human visual system tolerance to reduce the amount of encoded transform coefficients. It is very challenging to generate an optimal quantization value based on the contribution of the transform coefficient at each frequency order. The psychovisual threshold represents the sensitivity of the human visual perception at each frequency order to the image reconstruction. An ideal contribution of the transform at each frequency order will be the primitive of the psychovisual threshold in image compression. This research study proposes a psychovisual threshold on the large discrete cosine transform (DCT) image block which will be used to automatically generate the much needed quantization tables. The proposed psychovisual threshold will be used to prescribe the quantization values at each frequency order. The psychovisual threshold on the large image block provides significant improvement in the quality of output images. The experimental results on large quantization tables from psychovisual threshold produce largely free artifacts in the visual output image. Besides, the experimental results show that the concept of psychovisual threshold produces better quality image at the higher compression rate than JPEG image compression.