INFORMATICA International Journal Main Page Editorial Board Abstracting/Indexing Instructions to Authors Subscription Information Contents Author Index Papers in Production		INFORMATICA, 2012, Vol. 23, No. 1, 125-140 © Institute of Mathematics and Informatics, ISSN 0868-4952 Coding Algorithm for Grayscale Images Based on Piecewise Uniform Quantizers Milan S. SAVIC, Zoran H. PERIC, Milan R. DINCIC Faculty of Electronic Engineering, University of Nis Aleksandra Medvedeva 14, 18000 Nis, Serbia E-mail: malimuzicar@gmail.com, z.peric@elfak.ni.ac.rs, mdincha@hotmail.com Abstract In this paper, a piecewise uniform quantizer for input samples with discrete amplitudes for Laplacian source is designed and analyzed, and its forward adaptation is done. This type of quantizers is very often used in practice for the purpose of compression and coding of already quantized signals. It is shown that the design and the adaptation of quantizers for discrete input samples are different from the design and the adaptation of quantizers for continual input samples. A weighting function for PSQNR (peak signal-to-quantization noise ratio), which is obtained based on probability density function of variance of standard test images is introduced. Experiments are done, applying these quantizers for compression of grayscale images. Experimental results are very well matched to the theoretical results, proving the theory. Adaptive piecewise uniform quantizer designed for discrete input samples gives for 9 to 20 dB higher PSQNR compared to the fixed piecewise uniform quantizer designed for discrete input samples. Also it is shown that the adaptive piecewise uniform quantizer designed for discrete input samples gives higher PSQNR for 1.46 to 3.45 dB compared the adaptive piecewise uniform quantizer designed for continual input samples, which proves that the discrete model is more appropriate for image quantization than continual model. Keywords: piecewise uniform quantizer, input samples with discrete amplitude, forward adaptation, grayscale image To preview Lithuanian abstract see full article text To preview full article text in PDF format click here You could obtain free Acrobat Reader from Adobe
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