Existing image enhancement methods fall short of expectations because with them it is difficult to improve global and local image contrast simultaneously. To address this problem, we propose a histogram equalization-based method that adapts to the data-dependent requirements of brightness enhancement and improves the visibility of details without losing the global contrast. This method incorporates the spatial information provided by image context in density estimation for discriminative histogram equalization. To minimize the adverse effect of non-uniform illumination, we propose defining spatial information on the basis of image reflectance estimated with edge preserving smoothing. Our method works particularly well for determining how the background brightness should be adaptively adjusted and for revealing useful image details hidden in the dark.
Abstract. For accurate color reproduction of motion pictures or still pictures of moving objects, we developed a different one-shot sixband image-capturing and visualization system that combines multiband and stereo imaging techniques. The proposed system consists of two consumer-model digital cameras and an interference filter whose spectral transmittance is comb-shaped. Subpixel correspondence search between the stereo image pairs is conducted and image transformation whose parameters are estimated from the correspondence is used to correct the geometric relationship between the images. The Wiener estimation method is used for color reproduction. For experiments, we have constructed two six-band camera systems to evaluate the quality of resultant images. One is for capturing high-resolution images using digital single-lens reflex cameras. The other is for capturing motion pictures using digital video cameras, for which all image processing steps after image capture are implemented on graphics processing units and the frame rate of the system is 30 fps when image size is XGA. For both systems, the average color difference between the measurement data and estimation results for 24 color patches of the Macbeth ColorChecker™ is dEa à b à ¼ 1.21 at maximum.
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