An image encoder for outputting a bitstream by encoding an input image includes a predictive block, a machine learning based prediction enhancement (MLBE) block, and a subtractor. The predictive block is configured to generate a prediction block using data of a previous input block. The MLBE block is configured to transform the prediction block into an enhanced prediction block by applying a machine learning technique to the prediction block. The subtractor is configured to generate a residual block by subtracting pixel data of the enhanced prediction block from pixel data of a current input block.