Authors
Abstract
Abstract:
Digital images are widely used in computer applications. Uncompressed digital
images require considerable storage capacity and transmission bandwidth. Efficient image
compression solutions are becoming more critical with the recent growth of data intensive
and multimedia-based web application.
In this paper, Hybrid Differential Pulse Code Modulation (DPCM) in wavelet
domain and lossless methods (Huffman and Run length code) for image compression is
investigated. The image signal is composed into four scales (approximate, horizontal,
vertical and diagonal coefficients). The energy level of approximate is different from that of
detail information; therefore, the approximate is quantized alone and horizontal and vertical
are quantized alone by using the differential pulse code modulation (DPCM). In all
simulations the diagonal coefficients are discarded. Two types of coding are used, Huffman
code and run length coding (RLC) techniques. The results show that truncate horizontal
and vertical coefficients using hard threshold gives best performance than soft threshold
with gain about 3 dB to get the same compression ratio (CR). The wavelet based image
compression using Huffman code gives CR about 77% compared with RLC that gives CR
about 71% with suitable peak signal to noise ratio (PSNR).
Key words: image compression, discrete wavelet transforms (DWT), differential pulse
code modulation (DPCM), Huffman code and run length code (RLC)
Keywords
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