A method and apparatus for detecting a complex region of an image are disclosed. In one example, the method may involve calculating complexity values for a current block, a next block, and a previous block. The method may involve: (i) detecting that the previous complexity value is less than a first threshold value, and that the next complexity value is greater than a second threshold value; and (ii) determining that neither a transition to the current block nor a transition to the previous block is a flat-to-complex region transition. The method may involve detecting a flat-to-complex region transition when transitioning to the next block in response to (i) and (ii).