The present invention is directed to improve efficiency in use of a memory for storing display data which is used for an overdrive process. A display driver for driving a display device compresses image display data, stores the compressed data into a memory, and generates a preceding frame by decompressing the data read from the memory. A setting unit divides a display screen of the display device into, for example, a first region as a center part and a second region as a peripheral part. An overdrive computing unit generates overdrive display data in response to a present-time frame and the preceding frame, compresses the image display data in the first and second regions at first and second data compression ratios of small and large values, respectively, and stores the compressed data into the memory. By saving the space of the memory, the picture quality in the first region is improved.