Method and apparatus for encoding/decoding image using adaptive quantization step

An apparatus for encoding an image comprising:

• a prediction unit that generates a prediction block that is an intra or inter prediction value of a current block;
• a control unit that calculates a color difference between the current block and the generated prediction block;
• and
• an encoding unit that encodes the current block by adjusting a quantization step, based on the calculated color difference.

A method of decoding an image comprising:

• receiving a bitstream including data on a current block encoded by adjusting a quantization step based on a color difference, after a prediction block which is an intra or inter prediction value of the current block is generated and the color difference between the current block and the prediction block is calculated;
• extracting the data on the current block and information on the adjusted quantization step from the received bitstream;
• and
• inverse-quantizing the extracted data on the current block based on the information on the extracted quantization step.

A computer readable recording medium having embodied thereon a computer program for executing a method of decoding an image comprising:

• receiving a bitstream including data on a current block encoded by adjusting a quantization step based on a color difference, after a prediction block which is an intra or inter prediction value of the current block is generated and the color difference between the current block and the prediction block is calculated;
• extracting the data on the current block and information on the adjusted quantization step from the received bitstream;
• and
• inverse-quantizing the extracted data on the current block based on the information on the extracted quantization step.