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A new image enhancement algorithm based on nonsubsampled contourlet transform is presented. Low contrast images are transformed into multi-scale and multi-directional contour information, where a nonlinear mapping function is used to modify the contour coefficients at each level. The enhancement is achieved by amplifying weak edges and inhibiting the background noise while adjusting the dynamic range. Experiments show the proposed algorithm preserves the intrinsic geometrical information of the enhanced image and can be effectively applied to a wide range of image types under diverse illumination conditions.