Watermark information embedding device, watermark information processing system, watermark information embedding method, and program

A watermark information processing system, comprising:

• a watermark information embedding device and a watermark information extraction device, wherein
• the watermark information embedding device comprises:
• a first wavelet transformer for performing a wavelet transform on an original image of a two-dimensional code to decompose this image into various frequency components;
• a watermark information embedder for embedding watermark information, as a high-frequency component in the oblique direction, in a high-frequency component in the oblique direction out of the various frequency components decomposed by the first wavelet transformer;
• and
• an inverse wavelet transformer recomposing the two-dimensional code containing watermark information by performing an inverse wavelet transform on frequency components other than the high-frequency component in the oblique direction, out of the various frequency components decomposed by the first wavelet transformer, and the high-frequency component in the oblique direction in which the watermark information is embedded by the watermark information embedder, and
• the watermark information extraction device comprises:
• a two-dimensional code capturer for capturing an input image of the two-dimensional code containing watermark information recomposed by the inverse wavelet transformer;
• a second wavelet transformer for performing a wavelet transform on the input image of the two-dimensional code containing watermark information captured by the two-dimensional code capturer and producing the high-frequency components;
• and
• a watermark information extractor for extracting watermark information from a high-frequency component in an oblique direction out of the high-frequency components produced by the second wavelet transformer.

A watermark information embedding method, comprising:

• a first wavelet transform step for performing a wavelet transform on an original image of a two-dimensional code to decompose this image into various frequency components;
• a watermark information embedding step for embedding watermark information, as a high-frequency component in the oblique direction, in a high-frequency component in the oblique direction out of the various frequency components decomposed by the first wavelet transform step;
• and
• an inverse wavelet transform step for recomposing the two-dimensional code containing watermark information by performing an inverse wavelet transform on frequency components other than the high-frequency component in the oblique direction, out of the various frequency components decomposed by the first wavelet transform step, and the high-frequency component in the oblique direction in which the watermark information is embedded by the watermark information embedding step.

A non-transitory computer-readable recording medium storing a program for causing a computer to execute a procedure comprising:

• a first wavelet transform procedure for performing a wavelet transform on an original image of a two-dimensional code to decompose this image into various frequency components;
• a watermark information embedding procedure for embedding watermark information, as a high-frequency component in the oblique direction, in a high-frequency component in the oblique direction out of the various frequency components decomposed by the first wavelet transform procedure;
• and
• an inverse wavelet transform procedure for recomposing the two-dimensional code containing watermark information by performing an inverse wavelet transform on frequency components other than the high-frequency component in the oblique direction, out of the various frequency components decomposed by the first wavelet transform procedure, and the high-frequency component in the oblique direction in which the watermark information is embedded by the watermark information embedding procedure.