Patent ID: 7190807
Filing Date: 2007-03-13
Classification: G06T

Abstract:
1. A digital watermark extracting method comprising: an acquiring step of acquiring multi-value image data which represent an image which has been subjected in a state of binary image to embedding of a digital watermark and are obtained by a conversion into a multi-value state after said embedding; a pre-processing step of selecting one of plural threshold values for binarization and binarizing said multi-value image data with the selected threshold value; an extracting step of extracting the digital watermark from binary image data binarized in said pre-processing step; and a parity check step of performing a parity check of the digital watermark extracted in said extracting step; a storing step of storing in a memory means a digital watermark which is judged not to include an error as a result of the parity check; a repetition step of selecting an unselected threshold value from among the plural threshold values, and repeating the processes of said pre-processing step, said extracting step, said parity check step and said storing step for the selected threshold value; and an output step of specifying and outputting a final digital watermark by performing majority decision of each bit position on a bit train constituted by each of the plural digital watermarks stored in the memory means.