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US 2016/0110635 A1Published application
Halftone data-bearing encoding system and halftone data-bearing decoding system
AssigneeNational Taipei University of Technology
InventorsYung-Yao Chen, Kai-Wen Chen
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Abstract
An encoding system converts a grayscale image into an original halftone image according to a predetermined threshold matrix, determines carrier cells from the original halftone image according to reference dot patterns having rotationally asymmetric first-tone patterns, converts the carrier cells into encoded cells according to to-be-embedded codes and rotational states of corresponding asymmetric first-tone patterns, and optimizes non-carrier cells and encoded cells using a direct binary search technique to visually approach the grayscale image.
Claims16
An encoding system for generating a data-bearing image, said encoding system comprising:
- a halftoning module configured to convert an original grayscale image into an original halftone image by screening the original grayscale image using a predetermined threshold matrix that includes a plurality of grayscale threshold values, the original halftone image consisting of first-tone dots and second-tone dots and having a plurality of image cells each corresponding to the predetermined threshold matrix in size;
- a selecting module configured to select at least one of the image cells to be a carrier cell according to a set of reference dot patterns that corresponds with the predetermined threshold matrix, the carrier cell having a dot pattern identical to one of the reference dot patterns that has an asymmetric first-tone pattern consisting of a plurality of first-tone dots and being rotationally asymmetric;
- an encoding module configured to convert the carrier cell into an encoded cell according to a to-be-embedded code and at least two different rotational states of the asymmetric first-tone pattern that are respectively defined to represent different codes;
- a non-carrier cell optimizing module configured to optimize at least one non-carrier cell which is one of the image cells not determined to be the carrier cell by performing a direct binary search on each pixel of said at least one non-carrier cell until a minimum error from a portion of the original grayscale image that corresponds to said at least one non-carrier cell has been determined;
- and
- an encoded cell optimizing module configured to optimize the encoded cell by performing trials of a variety of displacements in a manner of the direct binary search on a first-tone pattern of the encoded cell that consists of a plurality of first-tone dots until a minimum error from a portion of the original grayscale image that corresponds to the encoded cell has been determined.
3 more elements
A decoding system for obtaining data from a data-bearing halftone image consisting of first-tone dots and second-tone dots, said decoding system comprising:
- a database that stores therein an original grayscale image corresponding to the data-bearing halftone image, a predetermined threshold matrix that includes a plurality of grayscale threshold values, and a set of reference dot patterns that corresponds with the predetermined threshold matrix, wherein at least one of the reference dot patterns has an asymmetric first-tone pattern consisting of a plurality of first-tone dots and being rotationally asymmetric, and at least two different rotational states of the asymmetric first-tone pattern are respectively defined to represent different codes;
- a selecting module configured to:
- convert the original grayscale image into an original halftone image by screening the original grayscale image using the predetermined threshold matrix, the original halftone image consisting of a plurality of first-tone dots and a plurality of second-tone dots and having a plurality of image cells each corresponding to the predetermined threshold matrix in size,
- select at least one of the image cells to be a carrier cell according to said at least one of the reference dot patterns that has the asymmetric first-tone pattern, and
- determine a data-bearing cell from the data-bearing halftone image according to the carrier cell thus determined;
- and
- a decoding module configured to determine one of the rotational states of the asymmetric first-tone pattern that corresponds to a dot pattern of the data-bearing cell, and to determine a code represented by said one of the rotational states thus determined.
4 more elements
A method for generating a data-bearing image from an original grayscale image, said method comprising the steps of:
- converting the original grayscale image into an original halftone image by screening the original grayscale image using a predetermined threshold matrix that includes a plurality of grayscale threshold values, the original halftone image consisting of first-tone dots and second-tone dots and having a plurality of image cells each corresponding to the predetermined threshold matrix in size;
- selecting at least one of the image cells to be a carrier cell according to a set of reference dot patterns that corresponds with the predetermined threshold matrix, the carrier cell having a dot pattern identical to one of the reference dot patterns that has an asymmetric first-tone pattern consisting of a plurality of first-tone dots and being rotationally asymmetric;
- converting the carrier cell into an encoded cell according to a to-be-embedded code and at least two different rotational states of the asymmetric first-tone pattern that are respectively defined to represent different codes;
- optimizing at least one non-carrier cell which is one of the image cells not determined to be the carrier cell by performing a direct binary search on each pixel of said at least one non-carrier cell until a minimum error from a portion of the grayscale image that corresponds to said at least one non-carrier cell has been determined;
- and
- optimizing the encoded cell by performing trials of a variety of displacements in a manner of the direct binary search on a first-tone pattern of the encoded cell that consists of a plurality of first-tone dots until a minimum error from a portion of the grayscale image that corresponds to the encoded cell has been determined.
3 more elements
Dependencies are inferred from the claim text.