Image processing method and device for restoring sub-information from composite image information

An image processing device embodied on non-transitory computer readable media and adapted to restore, from composite image information produced by a composite image producing device which embeds invisible sub-information into visible main image information to produce the composite image information, the sub-information, comprising:

• a color separation unit configured to separate the composite image information into a plurality of color components;
• extraction units each of which is configured to extract frequency components of the sub-information contained in a corresponding one of the plurality of color components;
• smoothing units each of which is configured to smooth the frequency components of the sub-information extracted by a corresponding one of the smoothing units;
• a selection unit configured to select one of the outputs of the smoothing units;
• a normalization unit configured to normalize the selected one of the outputs of the smoothing units;
• and
• an output unit configured to output the output of the normalization unit.

An image processing method of restoring sub-information from composite image information produced through a composite image producing process which involves producing invisible to-be-embedded information by the sub-information, key information used in restoring the sub-information and a color difference modulation process on the key information and embedding the invisible to-be-embedded information into visible main image information, the image processing method comprising:

• separating the composite image information into a plurality of color components;
• extracting frequency components of the to-be-embedded information from each of the separated color components of the main image information, the frequency components of the to-be-embedded information being regarded as the frequency components of the key information;
• smoothing the extracted frequency components of the key information in each of the plurality of color components;
• selecting one from among the results of the smoothing process for frequency components in the plurality of color components;
• normalizing the selected result of the smoothing process;
• and
• outputting the result of the normalizing process.

An image processing device embodied on non-transitory computer readable media and adapted to restore sub-information from composite image information produced by a composite image producing device which produces invisible to-be-embedded information by the sub-information, key information used in restoring the sub-information and a color difference modulation process on the key information and embeds the invisible to-be-embedded information into visible main image information, the image processing device comprising:

• a color separation unit configured to separate the composite image information into a plurality of color components;
• extraction units each of which is configured to extract frequency components of the to-be-embedded information contained in a corresponding one of the plurality of color components, the frequency components of the to-be-embedded information being regarded as the frequency components of the key information;
• smoothing units each of which is configured to smooth the frequency components of the key information extracted by a corresponding one of the smoothing units;
• a selection unit configured to select one of the outputs of the smoothing units;
• a normalization unit configured to normalize the selected one of the outputs of the smoothing units;
• and
• an output unit configured to output the output of the normalization unit.