A Bayes-spectral-entropy-based measure of camera focus using a discrete cosine transform
Pattern Recognition Letters
Low-Light Auto-Focus Enhancement for Digital and Cell-Phone Camera Image Pipelines
IEEE Transactions on Consumer Electronics
Removing the blocking artifacts of block-based DCT compressed images
IEEE Transactions on Image Processing
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Low contrast images are easily suffering from noise effect. As a result, it can witness many local false peaks in the graph of sharpness function. However, the presence of many local false peaks hinders the camera's passive auto-focus system to perform its function in locating the focused peak. This paper presents an improved variance based sharpness computation which can adapt to various degrees of noise. The proposed sharpness computation can bring in the local false peaks generated by noise influence, and therefore produce a well defined focused peak standing for the best focused image. The experimental results from several image sequences validate the effectiveness of our proposed method.