The invention describes a method for protecting the authenticity of an object, item, document, packaging and/or a label from imitation, forgery and theft, whereas during such marking by means of graphic halftone visually encoded image keeping qualitative-quantitative data of an subject and containing a hidden verification hash code in the form of a digital watermark (DWM), square data cells of the cross-linked structure of the graphic halftone image with identical brightness values are revealed in the entire area inside the revealed square data cell, thereafter a square-cross-linked mask is formed to store the base of the revealed readable data cells, the applied digital watermark (DWM) is read and opposed by means of comparison of the brightness of color components of the central of the revealed readable data cell against the arithmetic mean value of the brightness of the components of the eight neighbor squares surrounding the revealed readable data cell.

Methods and systems for securely rendering a security feature with image data to be printed, can involve providing within the image data, data relating to a group of spots, and within the image data, mixing spots of two or more spot sizes among the group of spots to embed information within a stochastic or frequency modulation halftone image. In an embodiment, operations may be implemented for rendering a part of the image with a first spot among the group of spots and a remaining portion of the image with a second spot among the group of spots, wherein the second spot is smaller in size than the first spot.

In an example, a method includes obtaining, by at least one processor, a first halftone screen tile having a first halftone pattern. In some examples, the method further comprises obtaining a second halftone screen tile having a second halftone pattern. The method may include determining a halftone screen having a predetermined spatial arrangement of the first and second halftone screen tiles, wherein the relative placement of the first and second halftone screen tiles in the predetermined spatial arrangement provides a signature for the halftone screen which when applied to image data provides a printed output in which the signature is discernible.

In an example, a method includes, at least one processor, in response to each of a plurality of requests, determining a halftone screen. Determining the halftone screen comprises encoding a signature pattern in the halftone screen, and halftone screens for different requests may be encoded with a different signature pattern. The halftone screen may be arranged such that, when applied to image data to provide a printed output, the pattern is discernible therein to provide a signature for the printed output.