Image encoding apparatus and method, image decoding apparatus and method, and non-transitory computer readable medium

An image decoding apparatus comprising:

• an input unit that receives, as an input, encoded image data;
• a cut-out unit that cuts out number-of-bit data and error data included in the encoded image data;
• a prediction error value decoder that decodes the number-of-bit data, decodes the error data by using the number-of-bit data, and calculates a prediction error value;
• and
• a pixel value calculating unit that calculates a pixel value of a pixel of interest by using the prediction error value.

A non-transitory computer readable medium storing a program causing a computer to execute a process, the process comprising:

• receiving, as an input, image data;
• calculating a predicted pixel value of a pixel of interest serving as a target to be processed in the image data;
• calculating a prediction error value by using an actual pixel value and the predicted pixel value of the pixel of interest;
• and
• encoding the prediction error value with information including a number of bits and an error value, and encoding, as the error value, only one or more most significant bits corresponding to a number of effective bits when the number of bits exceeds the number of effective bits.

An image encoding apparatus comprising:

• an input unit that receives, as an input, image data;
• a discrete cosine transform unit that performs discrete cosine transform of the image data;
• and
• an encoder that performs Huffman coding of coefficients of the discrete-cosine-transformed image data, the encoder encoding only one or more most significant bits corresponding to a number of effective bits when a number of additional bits of the Huffman coding exceeds the number of effective bits.

An image encoding method comprising:

• receiving, as an input, image data;
• calculating a predicted pixel value of a pixel of interest serving as a target to be processed in the image data;
• calculating a prediction error value by using an actual pixel value and the predicted pixel value of the pixel of interest;
• and
• encoding the prediction error value with information including a number of bits and an error value, and encoding, as the error value, only one or more most significant bits corresponding to a number of effective bits when the number of bits exceeds the number of effective bits.

An image decoding method comprising:

• receiving, as an input, encoded image data;
• cutting out number-of-bit data and error data included in the encoded image data;
• decoding the number-of-bit data, decoding the error data by using the number-of-bit data, and calculating a prediction error value;
• and
• calculating a pixel value of a pixel of interest by using the prediction error value.