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H. B. Kekre,Tanuja sarode,Shachi Natu 보안공학연구지원센터(IJSIP) 2014 International Journal of Signal Processing, Image Vol.7 No.6
In this paper a watermarking technique using hybrid wavelet transforms obtained from sinusoidal and non-sinusoidal component orthogonal transforms is proposed. Sinusoidal transform DCT and non-sinusoidal transforms Walsh, Haar and Discrete Kekre Transform are used to generate hybrid wavelet transforms namely DCT-Walsh, Walsh-DCT, DCT-Haar, Haar-DCT, DCT-DKT and DKT-DCT. Size of each component transform matrix is varied suitably from 4, 8, 16, 32, and 64 to generate hybrid wavelet transform matrix for host and watermark. The best size combination is further applied column wise and row wise to host and watermark and to embed the watermark middle frequency regions of host is selected. Embedding is first done without sorting the hybrid wavelet transform coefficients of host and watermark and then sorting is applied to observe the difference in the achieved robustness. Performance of proposed technique is evaluated against various attacks to decide whether sinusoidal transform when used as base transform matrix or local transform matrix is more robust.
Color Image Compression using DKT-DCT Hybrid Wavelet Transform in Various Color Spaces
H.B. Kekre,Tanuja Sarode,Prachi Natu 보안공학연구지원센터 2014 International Journal of Signal Processing, Image Vol.7 No.5
This paper proposes image compression in different color spaces using hybrid wavelet transform. To generate hybrid wavelet transform Discrete Kekre transform (DKT) and Discrete Cosine transform (DCT) are selected as component transforms. Due to high energy compaction property, DCT is selected as local component transform that contributes to local features of an image. Hybrid wavelet transform extracts features of both the component transforms and hence gives less error and better image quality. Component transforms of different sizes are selected to generate hybrid wavelet of size 256x256 and applied on images. In RGB color space 16-16 combination i.e. hybrid wavelet generated using DKT 16x16 and DCT 16x16 gives least error than other combinations like 8-32, 32-8 and 64-4. RMSE, MAE, AFCPV and Structural Similarity Index (SSIM) are the error metrics used to measure reconstructed image quality. Different color spaces have been used to observe the performance of this hybrid wavelet transform. In KLUV color space minimum RMSE and MAE is observed than RGB, YUV, YCbCr, XYZ and YIQ color space. Whereas RGB color space gives lowest AFCPV than other color spaces using 16-16 component size. Hence SSIM is used to eliminate this inconsistency in these traditional error metrics. KLUV color space gives highest SSIM 0.998 which is closest to maximum one proving it as a better choice than other color spaces.