1. An image processing method of an image processing apparatus, the method comprising: obtaining a reference block a having a first resolution and a differential block having the first resolution; transforming a resolution of a prediction block having the first resolution and a resolution of the differential block having the first resolution in order to generate a prediction block having a second resolution and a differential block having the second resolution, the prediction block having the first resolution and the differential block having the first resolution being generated based on a pixel value of the reference block having the first resolution; and synthesizing the generated prediction block having the second resolution and the generated differential block having the second resolution in order to generate a target block having the second resolution.