A Novel Algorithm for Satillite Image Resolution Enhancement Based on Dual-tree Complex Wavelet Transform (dt-cwt) and Nonlocal Means (nlm)

The Resolution enhancement (RE) schemes (which are not based on wavelets) has one major drawback of losing high frequency contents (which results in blurring). The discrete wavelettransform-based (DWT) RE scheme generates artifacts (due to a DWT shift-variant property). A wavelet-domain approach based on dual-tree complex wavelet transform (DT-CWT) and nonlocal means (NLM) is proposed for RE of the satellite images. A satellite input image is decomposed by DT-CWT (which is nearly shift invariant) to obtain high-frequency sub bands. Here the Lanczos interpolator is used to interpolate the high-frequency sub bands and the low-resolution (LR) input image. The high frequency sub bands are passed through an NLM filter to cater for the artifacts generated by DT-CWT (despite of its nearly shift invariance). The filtered high-frequency sub bands and the LR input image are combined using inverse DT-CWT to obtain a resolution-enhanced image. Objective and subjective analyses show superiority of the new proposed technique over the conventional and state-of-the-art RE techniques.