Data processing apparatus, image processing apparatus, and method therefor

Abstract

Watermark data that indicate additional information, such as copyright information, are optimized in accordance with the contents of object data, and the watermark data is embedded in image data. An image dividerdivides image data Vi into image blocks Iij, and corresponds a selected basic pattern Phij with each of the image blocks Iij. Orthogonal transformation unitsandgenerate DFT coefficients I'ij and P′hij, and power element calculatorsandgenerate power elements I″ij and P″ij. A basic pattern adjustment unitadjusts the coefficient of P′hij to generate P′hijto P′hijn. A watermark pattern generatorcalculates variations before and after P′hijto P′hijn are embedded in I″ij, and selects, from P′hijto P′hijn, P′″hijto P′″hijthat provide variations equal to or smaller than the threshold value e. Then, the watermark pattern generatorselects, as a watermark pattern P′ij, the pattern that is most easily detectable, and a pattern embedding unitthat adds P′ij to I′ij.