Halftone data-bearing encoding system and halftone data-bearing decoding system

摘要

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.

主权项

1. 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.