Patent ID: 8023160

Claim:
A method for embedding data in an image via halftone dot orientation, the method comprising: receiving a cover contone image having an intensity value associated with each pixel location of said image, a data message is to be embedded in said received image, said message comprising a plurality of data values, each single data value taking only one unique state from a set of possible values; defining a uniform periodic tiling for said image, each of said uniform tiles having identical dimensions and encompassing an array of pixel intensity values; for each unique state, defining an array of threshold values, each array of threshold values having a one-to-one correspondence with each array of pixel intensity values, and wherein each of said threshold values in said threshold array is defined for a given screen frequency and a given dot shape; for each single data value of said message, identifying a unique uniform periodic tile wherein a single data value is to be embedded; for each identified unique periodic tile wherein a current single data value is to be embedded, comparing each intensity value in said periodic tile with a corresponding value of said threshold array defined for the unique state of said current single data value, said comparison producing a binary output value for each pixel location in said current tile, all of said comparisons collectively producing a binary mask for said periodic tile; and rendering said image, each unique periodic tile wherein a single data value is to be embedded is rendered according to said binary mask produced for that tile.