Transform Coefficient Histogram-Based Image Enhancement Algorithms Using Contrast Entropy August 21, 2015 S.S. Agaian, B. Silver, and K.A. Panetta, IEEE Trans Image Process, vol. 16, pp. 741-58, March 2007. contrast measure, discrete cosine transform (DCT), discrete Fourier transform (DFT), human vision system (HVS), image enhancement, transform histogram