IMAGE ENCODER, IMAGE ENCODING PROGRAM, IMAGE DECODER, AND IMAGE DECODING PROGRAM

摘要

PROBLEM TO BE SOLVED: To add/separate private information to/from an image while suppressing deterioration in image quality as much as possible in a way that the insertion of the private information is hardly known by a third party.

SOLUTION: A private information insertion discrimination section 5 discriminates whether or not the private information is to be inserted to a high frequency component of a luminance component of a quantized DCT coefficient, wherein the section 5 discriminates the insertion of the private information depending on whether or not an average value of the luminance component of a reference block signal is greater than a preset threshold value. A color difference signal private information insertion discrimination section 6 discriminates whether or not the private information is to be inserted to a high frequency component of a color difference component of the quantized DCT coefficient. When the private information insertion discrimination section 5 discriminates the insertion of the private information, the color difference signal private information insertion discrimination section 6 replaces the high frequency component specified in advance in the quantized DCT coefficient of the supplied luminance component with the private information. When the color difference signal private information insertion discrimination section 6 discriminates the insertion of the private information, the color difference signal private information insertion discrimination section 6 replaces the high frequency component specified in advance in the quantized DCT coefficient of the supplied color difference component with the private information.

COPYRIGHT: (C)2003,JPO