We describe a device that dynamically increases the contrast of the effective gray level based on the gray level distribution of serial images, performs soft-transfer of dynamic contrast adjustment curve when a scene switch occurs thereby realizing adaptive contrast enhancing while effectively avoiding image flicker. A device and associated method for enhancing image contrast includes a gray level distribution statistic circuit to calculate gray level statistic data of an image responsive to an image brightness signal. An adaptive contrast mapping curve calculation circuit calculates a gray level mapping curve responsive to the gray level statistic data. An inter-frame curve soft-merging circuit performs inter-frame soft-merging to the gray level mapping curve. And a gray level mapping circuit performs gray level mapping of the input image brightness signal.