1. An apparatus for dynamic contrast enhancement, comprising: a histogram calculator for receiving an input image to generate a luma histogram, wherein the input image includes a plurality of pixels; a feature value calculator for performing high-pass filtering operations over the plurality of pixels to obtain a high-frequency component for each pixel and for generating a feature value for each pixel according to its corresponding high frequency component and a first relation curve to generate a feature histogram; a first combining unit coupled to the histogram calculator and the feature value calculator for calculating an inverse parameter according to the sum of feature values and a second relation curve and for combining the luma histogram with the feature histogram to generate a combined histogram according to the inverse parameter; a histogram equalizer for receiving the combined histogram and performing contrast adjustment and integral operations to generate a equalized transfer curve; and a remapper for remapping the input image to generate a contrast enhanced image according to a final transfer curve; wherein the first relation curve is a feature value-high frequency component characteristic curve and has a maximum feature value in a middle high frequency component range and a minimum feature value in a large high frequency component range and a small high frequency component range; and wherein the inverse parameter is in reverse proportion to the sum of feature values according to the second relation curve.