IMAGE CORRECTION METHOD, IMAGE CORRECTION APPARATUS CAPABLE OF USING THE METHOD AND DIGITAL WATERMARK EXTRACTING APPARATUS

摘要

PROBLEM TO BE SOLVED: To solve the problem that distortion occurs when a print image where a digital watermark is embedded is photographed, and therefore it is difficult to correctly detect the digital watermark. SOLUTION: A photographing part 30 photographs and computerizes a print image P where a digital watermark is embedded and a grid pattern image R. An image region judging part 32 judges an original image region in a photographed image. A profile generating part 38 acquires the coordinate values of the vertexes of the respective grids of the grid pattern image R deformed due to lens distortion or fluoroscopy distortion, and generates grid-shaped profile data and registers it in a profile data base 40. An image correcting part 34 corrects distortion which occurs in the original image region of the print image P based on the grid-shaped profile data. A watermark extracting part 36 divides the distortion-corrected original image region into blocks, and detects watermark bits embedded in each block to thereby extract watermark information X. COPYRIGHT: (C)2005,JPO&NCIPI