An image processing apparatus including a memory storing instructions, and a processor configured to operate based on the instructions to reconstruct a current block from encoded data of the current block, obtain a quantization error map including sample values calculated based on a quantization parameter included in the encoded data, obtain a first modified block by applying the current block and the quantization error map to a neural network, obtain a first differential block between the current block and the first modified block, obtain a second differential block by changing sample values of the first differential block based on a parameter dependent on a feature of the current block, and obtain a second modified block by combining the current block and the second differential block.