Document watermarking method using line margin shifting
OwnerJoe Pasquainventor
Life of this patent
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Abstract
A method is provided for watermarking a document using line margin shifting. The method shifts the left margin of lines of text either right or left to encode a watermark in a textual document. To embed the watermark, certain lines of the text are selected to carry watermark information. These lines are shifted either right or left to indicate a 1 or 0.
Claims5
A method for detecting a watermark in a document, comprising:
- loading a page image of a watermarked document;
- locating a set of scanlines in the watermarked page image;
- calculating a detection value;
- loading a page image of an original document;
- locating a set of scanlines in the original page image;
- calculating a target value;
- and
- determining a difference between the target value and the detection value.
A method for watermarking a document, comprising:
- determining a watermark value;
- determining a watermark key;
- determining a watermark line based on the watermark key;
- and
- shifting a left margin of the watermark line based on the watermark value.
A computer-readable medium having stored thereon a plurality of sequences of instructions for watermarking a document, the plurality of sequences of instructions including sequences of instructions, which, when executed by a processor, cause the processor to perform the steps of:
- determining a watermark value;
- determining a watermark key;
- determining a watermark line based on the watermark key;
- and
- shifting a left margin of the watermark line based on the watermark value.
Dependencies are inferred from the claim text.