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Hybrid Transform, Haar Wavelet, SSIM, MAE, Image Compression.

A novel image compression using hybrid Haar wavelet transform has been proposed in this paper. Hybrid wavelet transform is generated using two different orthogonal transforms. Haar transform acts as a base transform and other sinusoidal transforms like DCT, DST, Hartley and Real-DFT are paired with Haar transform to generate hybrid Haar wavelet. Among these four pairs Haar-DCT hybrid wavelet gives lower error as compared to Haar-DST, Haar-Hartley and Haar-Real-DFT. Performance of Haar-DCT hybrid wavelet is further analyzed using multi resolution hybrid wavelet and Haar-DCT hybrid transform. Experimental results show that hybrid wavelet with component size 16-16 gives lower error at higher compression ratios than multi resolution analysis and hybrid transform performance. Performance is measured using RMSE which is traditional parameter to measure error. Lowest RMSE obtained is 9.77 at compression ratio 32 using Haar-DCT Hybrid Wavelet with component size 16-16. Various other error metrics like MAE, AFCPV and SSIM are used to measure error. Lowest MAE and AFCPV are observed at compression ratio 32 are in Haar (16x16) –DCT (16x16) hybrid wavelet having values 6.86 and 0.31 respectively. When blocked SSIM is applied on 16-16 Haar-DCT hybrid wavelet it gives value 0.993 at compression ratio 32 which is closer to one indicating that good quality of compressed image is obtained.