System and method for automatic identification of photocopied documents
AssigneeSotec Consulting Sl
InventorsArmando Munoz Utiel, David Gonzalez Garcia
Life of this patent
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Abstract
A system and method for automatic identification of photocopied documents is disclosed wherein the method is performed by capturing an image of a marked printed document; decoding a digital watermark embedded in the image, obtaining a mark identifier; recovering, by searching a database, at least one calibration parameter associated with the mark identifier; applying a discrete Fourier transform to the image, obtaining a frequency matrix; obtaining at least one maximum frequency value in the frequency matrix; comparing the at least one maximum frequency value with at least one calibration parameter; determining, on the basis of the comparison, if the marked printed document is an original document or a photocopied document.
Claims16
A method for automatic identification of photocopied documents, comprising:
- capturing an image of a marked printed document with a digital watermark;
- obtaining, from the captured image, a calibration identifier;
- recovering, by searching a database, a calibration threshold associated with the calibration identifier;
- applying a discrete Fourier transform to the image, obtaining a frequency matrix;
- converting the frequency matrix to a logarithmic scale;
- binarizing the matrix converted to a logarithmic scale, so that the matrix values above a predetermined binarization threshold correspond to frequency maximums;
- measuring the area, defined in number of pixels, of the frequency maximums that appear in the binarized frequency matrix, obtaining a maximum frequency value for each frequency maximum;
- comparing the maximum frequency value of each frequency maximum with the calibration threshold;
- determining, on the basis of the comparison, if the marked printed document is an original document or a photocopied document.
A system for automatic identification of photocopied documents, comprising:
- an image acquisition device configured for capturing an image of a marked printed document with a digital watermark;
- a photocopied document identification device comprising a data processing unit configured for:
- receiving the image captured by the image acquisition device;
- obtaining, from the image, a calibration identifier;
- recovering, by searching a database, a calibration threshold associated with the calibration identifier;
- applying a discrete Fourier transform to the image, obtaining a frequency matrix;
- converting frequency matrix to a logarithmic scale;
- binarizing the matrix converted to a logarithmic scale, so that the matrix values above a predetermined binarization threshold correspond to frequency maximums;
- measuring the area, defined in number of pixels, of the frequency maximums that appear in the binarized frequency matrix, obtaining a maximum frequency value for each frequency maximum;
- comparing the maximum frequency value of each frequency maximum with the calibration threshold;
- determining, on the basis of the comparison, if the marked printed document is an original document or a photocopied document.
Dependencies are inferred from the claim text.