An electronic device comprising: a display comprising a display panel; a processor configured to: generate image data in which pieces of independent partial image data are concatenated, and encode the image data in a specified scheme; store the encoded image data in a graphic random access memory, GRAM; and enter a sleep mode after storing the encoded image data in the GRAM; and a display driver integrated circuit for driving the display, wherein the display driver integrated circuit comprises the GRAM configured to store the encoded image data, and wherein, while the processor is in the sleep mode, the display driver integrated circuit is configured to: select a plurality of pieces of independent partial image data from the stored encoded image data; decode the selected plurality of pieces of partial image data; and output the selected plurality of pieces of partial image data to a specified sub area of the display panel, wherein the selecting, decoding and outputting includes repeatedly selecting, decoding, and outputting different pieces of partial image data from the stored encoded image data based on a specified sequence, wherein each selected piece of partial image data is sequentially output to the same specified sub area of the display panel to replace the image data currently output to the specified sub area of the display panel, and wherein, when in the sleep mode, the processor does not store image data in the GRAM a display comprising a display panel; a processor configured to: generate image data in which pieces of independent partial image data are concatenated, and encode the image data in a specified scheme; store the encoded image data in a graphic random access memory, GRAM; and enter a sleep mode after storing the encoded image data in the GRAM; and generate image data in which pieces of independent partial image data are concatenated, and encode the image data in a specified scheme; store the encoded image data in a graphic random access memory, GRAM; and enter a sleep mode after storing the encoded image data in the GRAM; and a display driver integrated circuit for driving the display, wherein the display driver integrated circuit comprises the GRAM configured to store the encoded image data, and wherein, while the processor is in the sleep mode, the display driver integrated circuit is configured to: select a plurality of pieces of independent partial image data from the stored encoded image data; decode the selected plurality of pieces of partial image data; and output the selected plurality of pieces of partial image data to a specified sub area of the display panel, wherein the selecting, decoding and outputting includes repeatedly selecting, decoding, and outputting different pieces of partial image data from the stored encoded image data based on a specified sequence, wherein each selected piece of partial image data is sequentially output to the same specified sub area of the display panel to replace the image data currently output to the specified sub area of the display panel, and wherein, when in the sleep mode, the processor does not store image data in the GRAM select a plurality of pieces of independent partial image data from the stored encoded image data; decode the selected plurality of pieces of partial image data; and output the selected plurality of pieces of partial image data to a specified sub area of the display panel, wherein the selecting, decoding and outputting includes repeatedly selecting, decoding, and outputting different pieces of partial image data from the stored encoded image data based on a specified sequence, wherein each selected piece of partial image data is sequentially output to the same specified sub area of the display panel to replace the image data currently output to the specified sub area of the display panel, and wherein, when in the sleep mode, the processor does not store image data in the GRAM