ISSN : 1796-2048
Volume : 3    Issue : 1    Date : May 2008

Adaptive AC-Coefficient Prediction for Image Compression and Blind Watermarking
K.Veeraswamy and S.Srinivas kumar
Page(s): 16-22
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In this work, an adaptive image compression algorithm is proposed based on the prediction of AC
coefficients in Discrete Cosine Transform (DCT) block during reconstruction of image. In the
prediction phase, DC values of the nearest neighbour DCT blocks is utilized to predict the AC
coefficients of centre block. Surrounding DC values of a DCT blocks are adaptively weighed for AC
coefficients prediction. Linear programming is used to calculate the weights with respect to the
image content. Results show that this method is good in terms of good Peak Signal to Noise Ratio
(PSNR) and less blocking artifacts. The proposed scheme has been demonstrated through several
experiments including Lena. Reconstructed image is of good quality with same compression ratio
compared to the existing technique in the literature. In addition, an image watermarking algorithm is
proposed using DCT AC coefficients obtained. The performance of the proposed watermarking
scheme is measured in terms of PSNR and Normalized Cross Correlation (NCC). Further, this
algorithm is robust for various attacks including JPEG compression on watermarked image.

Index Terms
Image compression, DCT, linear programming, watermarking.