Abstract
This paper presents a hybrid wavelet transform technique which studies the effect of global components on the quality of image compression. Hybrid wavelet transform is generated using two different component orthogonal transforms. One orthogonal transform represents global featuresof image in betterway and another is used to represent local features. Walsh transform of size 8x8 is used as a base transform i.e. to represent global characteristics of image. Other transforms like DCT, Discrete Real Fourier Transform,DiscreteHartley transform (DHT), Discrete Sine Transform (DST), Discrete Kekre Transform (DKT) and Slant transform of size 32x32 are used to focus on local characteristics of an image.256x256 hybrid wavelet transform is generated and multiple iterations of global components are included using columns of base transform and its effect on reconstructed image quality is observed in terms of Root Mean Square Error (RMSE) and Peak Signal to Noise Ratio (PSNR). Â From the experiments it has been observed that when DCT is used to extract local features, best results are obtained among all combinations with Walsh transform. These results are also compared with Walsh transform and observed to be much superior at higher compression ratios giving better image quality.
Highlights
Discrete Walsh transform (DWT) is selected as base transform and DCT is used to extract local features of an image.Contribution of global components is increased by varying the iterations in generation of transformation matrix as mentioned in section I of proposed technique
This paper presents hybrid wavelet transform based image compression technique where hybrid wavelet transform matrix contributing different levels of global components can be generated
Walsh transform is used as base transform matrix and it is combined with different orthogonal component transforms that contribute to local features of an image
Summary
These rows represent global components in hybrid wavelet transform. Fig2: Hybrid Wavelet Transform Matrix with first ‘2M’ rows representing global components of image. 8. Vary the contribution of global components and regenerate hybrid wavelet transform matrix TAB.
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