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

#This application claims priority of Taiwanese Application No. 103136131, filed on Oct. 20, 2014.

#The disclosure relates to data encoding/decoding, and more particularly to an encoding/decoding system for bearing data in a halftone image.

#Barcode systems have been widely used in various aspects, such as automated logistic management, anti-counterfeit, labels, etc. In one application, a two-dimensional barcode or a QR code may be provided/printed on a poster or digital contents for protecting copyrighted content from illicit and unauthorized use. However, the additional printed barcode or QR code may adversely affect the overall esthetics of posters or digital contents.

#Other features and advantages of the disclosure will become apparent in the following detailed description of the embodiment with reference to the accompanying drawings, of which:

#FIG. 1 is a schematic diagram illustrating four shifted versions of a cell of a halftone image using a conventional data-bearing encoding method;

#FIG. 2 is a schematic diagram illustrating application of a direct binary search to a cell of a halftone image;

#Before the disclosure is described in greater detail, it should be noted that like elements are denoted by the same reference numerals throughout the disclosure.

#Referring to FIGS. 3 to 6, the embodiment of an encoding system of this disclosure is configured to generate a data-bearing halftone image according to an inputted original grayscale image 10, and includes a halftoning module 21, a carrier cell selecting module 22, an encoding module 23, a non-carrier cell optimizing module 24 and an encoded cell optimizing module 25. In this embodiment, the original grayscale image 10 is exemplified using a portion of a to-be-encoded image and has 8×8 pixels. The halftoning module 21 converts the original grayscale image 10 into an original halftone image 11 according to a predetermined square threshold matrix 26, which is a clustered-dot threshold matrix.

#In detail, the square threshold matrix 26 of this embodiment is a 4×4 clustered-dot screen having a screen tile vector set that consists of two two-dimensional vectors [0,4], [4,0] and has 4×4 grayscale threshold values. The halftoning module 21 divides the original grayscale image 10 into four grayscale cells 101 each having 4×4 pixels, and compares the grayscale cells 101 with the threshold matrix 26 one by one along a direction from left to right and from top to bottom. For each grayscale cell 101, the halftoning module 21 compares each pixel thereof with one of the threshold values at a corresponding location of the threshold matrix 26, followed by outputting “1” to represent a first-tone dot when the grayscale of the pixel is greater than or equal to the corresponding grayscale threshold value, and outputting “0” to represent a second-tone dot when the grayscale of the pixel is smaller than the corresponding grayscale threshold value. In this embodiment, the first-tone dots are exemplified as white dots, and the second-tone dots are exemplified as black dots, but the present disclosure is not limited thereto. Thus, the original grayscale image 10 is converted into the original halftone image 11 consisting of first-tone and second-tone dots, and having a plurality of image cells 111 each having a corresponding dot pattern. Each image cell 111 is equal in size (i.e., number of pixels) with each grayscale cell 101.