IMAGE DECODER, IMAGE DECODING METHOD AND COMPUTER PROGRAM PRODUCT FOR THE SAME

According to an embodiment of the invention, there is provided an image decoder for decoding encoded image data in an image block unit, including: a storage device configured to store a DC component of a past image block coefficient as a prediction value; a predict circuit configured to predict a DC component of a current image block coefficient using the prediction value; an inversely quantizing circuit configured to inversely quantize an image block coefficient outputted from the predict circuit; and a saturation processing circuit to execute a saturation processing of an image block coefficient outputted from the inversely quantizing circuit. A DC component of the image block coefficient outputted from the inversely quantizing circuit and a DC component of the image block coefficient after execution of the saturation processing are respectively inputted to the storage device.