1. A method of entropy-encoding image data, the method comprising: setting a current context model for entropy-encoding a syntax element of a first block of the image data and a second context model for entropy-encoding a syntax element of a second block of the image data that is adjacent to the first block to be the same as a previous context model used to entropy-encode the syntax element of a previously encoded block that is adjacent to the first block; and entropy-encoding the syntax element of the first block and the syntax element of the second block based on the current context model.