Abstract: An embodiment of a method for encoding a source image comprising multiple data units, performed by an image encoding unit, comprises the following steps. A quantized DC coefficient and multiple AC coefficients of a data unit are generated. A value at the (0,0) element of the first data unit is determined according to the quantized DC coefficient. A variable length coding (VLC) stream of the data unit is generated by encoding the determined value and the AC coefficients. An encoded bitstream comprising a restart mark followed by the VLC stream of the data unit is generated. An offset pointing to the beginning of the restart mark of the encoded bitstream is stored in a random access table. A compression image comprising the encoded bitstream and the random access table is generated.

Abstract: An embodiment of a method for decoding large images performed by a processing unit, comprises the following steps. A compressed bit stream of a minimum code unit (MCU) of an image is acquired. The acquired bit stream is decoded by performing a first stage of a image decoding procedure to generate a temporary decoding result of the acquired bit stream. It is determined whether the MCU requires display. If so, the generated temporary decoding result is decoded by performing a second stage of the image decoding procedure to generate display data of the acquired bit stream. The temporary decoding result of the acquired bit stream is utilized to decode another MCU of the bit stream.

Abstract: An embodiment of a method for encoding a source image comprising multiple data units, performed by an image encoding unit, comprises the following steps. A quantized DC coefficient and multiple AC coefficients of a data unit are generated. A value at the (0,0) element of the first data unit is determined according to the quantized DC coefficient. A variable length coding (VLC) stream of the data unit is generated by encoding the determined value and the AC coefficients. An encoded bitstream comprising a restart mark followed by the VLC stream of the data unit is generated. An offset pointing to the beginning of the restart mark of the encoded bitstream is stored in a random access table. A compression image comprising the encoded bitstream and the random access table is generated.

Abstract: An embodiment of a method for decoding large images performed by a processing unit, comprises the following steps. A compressed bit stream of a minimum code unit (MCU) of an image is acquired. The acquired bit stream is decoded by performing a first stage of a image decoding procedure to generate a temporary decoding result of the acquired bit stream. It is determined whether the MCU requires display. If so, the generated temporary decoding result is decoded by performing a second stage of the image decoding procedure to generate display data of the acquired bit stream. The temporary decoding result of the acquired bit stream is utilized to decode another MCU of the bit stream.