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US 6,959,098 B1Granted
Method and system for determining image transformation
AssigneeDigimarc Corporation
InventorAdnan M. Alattar
Life of this patent
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Abstract
A watermark decoding method makes use of a line-finding algorithm (e.g., the Radon transform) to determine rotation of an image from an initial orientation. Once rotation has been characterized, differential scaling of the image can readily be determined.
Claims6
A method of watermark decoding that includes:
- providing a set of input image data;
- applying an edge detection algorithm to the image data to yield a processed image;
- sensing linear energy in the processed image along more than two different angles;
- identifying an angle yielding an extrema of energy;
- and
- decoding a watermark from the input image data by reference to said angle.
3 more elements
A method of decoding a watermark from an image, including:
- providing a set of data representing the image in the frequency domain;
- compensating said set of data for a rotation factor;
- correlating said compensated set of data with a reference signal;
- and
- determining, based on said correlation, differential scaling of said image;
- and
- by reference to said determined differential scaling, decoding a watermark from the image.
4 more elements
Dependencies are inferred from the claim text.