Low‐contrast satellite images enhancement using discrete cosine transform pyramid and singular value decomposition

This study presents a satellite image contrast enhancement technique based on the discrete cosine transform (DCT) pyramid and singular value decomposition (SVD), in contrast to the methods based on wavelet decomposition and SVD which could fail to produce satisfactory results for some low‐contrast images. With the proposed method, an input image is decomposed into a low sub‐band image and reversed L‐shape blocks containing the high‐frequency coefficients of the DCT pyramid. The singular value matrix of the equalised low sub‐band image is then estimated from the combination between the singular matrix of the low sub‐band image and the singular matrix of its global histogram equalisation. The qualitative and quantitative performances of the proposed technique are compared with those of conventional image equalisation such as general histogram equalisation and local histogram equalisation, as well as some state‐of‐the‐art techniques such as singular value equalisation technique. Moreover, the proposed technique is contrasted against the technique based on the discrete wavelet transform (DWT) and SVD (DWT–SVD) as well as the technique based on DCT–SVD. The experimental results show that the proposed method outperforms both conventional and the state‐of‐the‐art techniques.