Conditions for Color Misregistration Sensitivity in Clustered-dot Halftones

Oztan, Basak; Sharma, Gaurav; Loce, Robert P.

doi:10.1109/icip.2007.4379994

Cited by 9 publications

(9 citation statements)

References 9 publications

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“…A simple and useful analytic threshold function for generating periodic clustered-dot halftones is obtained as a generalization of [12,13] as [14] T (x) = cos 2πf T 1 x +cos 2πf T 2 x . In order to embed the watermark patterns, we modulate the phase of the cosine functions as Fig.…”

Section: Multiplexed Halftone Watermarking Using Bi-directional Phasementioning

confidence: 99%

Multiplexed clustered-dot halftone watermarks using bi-directional phase modulation and detection

Oztan

Sharma

2010

2010 IEEE International Conference on Image Processing

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We present a method for embedding and detection of visual watermark patterns in printed images that use clustered-dot halftones in the printing process. The method allows two independent watermark patterns to be multiplexed, i.e. embedded in the same region of the printed image, thereby offering an improvement over prior techniques. The watermark patterns are embedded via phase modulation along the two periodicity directions of the halftone. Each embedded pattern can be visually detected, without interference from the other watermark, when the printed image, or a scan thereof, is overlaid with a decoder mask consisting of periodic lines oriented along the corresponding halftone periodicity direction. We experimentally demonstrate that our proposed multiplexing technique is effective. We also present analysis that demonstrates that the embedding has minimal visual impact and explains the pattern observed in the watermark detection process.Index Terms-Halftone watermarks, clustered-dot halftones, halftone phase modulation, print watermarks INTRODUCTIONHardcopy watermarks have been extensively used for content authentication and counterfeit protection for over seven centuries [1,2]. Paper watermarks, which represent the most prevalent form of hardcopy watermarks, are embedded within the printing substrate at the time of manufacture [2, Chap. 3]. As digital printing methods become commonplace, the flexibility that these methods offer over conventional analog printing has also been exploited in order to develop a number of alternative digital watermarking methods for hardcopy prints.Halftoning is typically utilized for the reproduction of images in most digital printing systems [3] and many of the digital hardcopy watermarking techniques exploit the characteristics of the halftoning process for embedding watermarks in the printed images [4][5][6][7][8][9][10]. A majority of these methodologies [4][5][6][7][8] mimic the conventional paper watermarks and utilize visual watermark patterns such as bi-level text images or logos. The watermarks are embedded in the form of changes in the halftone structures that are normally imperceptible but can be revealed by appropriate detection methods.In this paper, we present a technique that enables embedding and detection of two independent visual watermark patterns in the same region of a halftone image. Our technique is specifically designed for periodic clustered-dot halftones that are widely utilized in electrophotographic (laser) and lithographic (offset) printing. Based on the analogy with multiplexing in communications, we refer to

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Section: Multiplexed Halftone Watermarking Using Bi-directional Phasementioning

confidence: 99%

Multiplexed clustered-dot halftone watermarks using bi-directional phase modulation and detection

Oztan

Sharma

2010

2010 IEEE International Conference on Image Processing

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“…Furthermore, with larger dots, the color shift induced by the misregistration of the different layers has less undesirable effects. 27 …”

Section: Maximum Number Of Colorants (Metallic Inks) Per Colormentioning

confidence: 99%

Color Reproduction of Metallic-Ink Images

Babaei¹,

Hersch²

2016

jist

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Abstract. We study the color reproduction of full-color metallic-ink images. Full-color metallic-ink images are prints whose contributing colorants are exclusively made of colored metallic inks. Due to the presence of metallic particles, metallic inks show a metal-like luster. These particles are opaque and hide the underlying ink or substrate. In order to obtain predictable halftone colors, we need a juxtaposed halftoning method to create halftone dots of different colors side by side without overlapping. Juxtaposed halftoning invalidates many assumptions generally made for the color-reproduction workflow. For printing metallic-ink images, one needs a color-separation system creating surface coverages for the eight metallic inks that correspond to the eight Neugebauer primaries. For this purpose, we introduce a simple and fast method for N-color separation that relies either on Demichel's or on a variant of Kueppers' ink-to-colorant separations. Thanks to a unique set of ink-to-colorant formulas, pseudo-CMY ink values are separated into amounts of printable colorants. We also describe color-separation procedures that are able to optimize different properties of the resulting metallic-ink images. INTRODUCTIONA common element present in all printing applications is the color-reproduction workflow. A color-reproduction workflow converts an input image into the printer's command language. 1 Most existing reproduction workflows follow the steps shown in Figure 1. Briefly, input colors are first converted from a source color space, such as sRGB, into a device-independent color space such as CIELAB. 2 By performing gamut mapping, 3 the input colors are mapped into the colors of the usually narrower print gamut. Then, the color separation is carried out by converting the gamut-mapped printable colors into amounts of printer inks. The separated ink layers are then halftoned and printed.We can use a spectral prediction model for color separation and gamut mapping. The forward prediction model expresses the forward characterization. It determines the printer's color response to input control values, e.g. the amount of inks to be printed. By varying the amount of inks in the forward model, we can determine the color gamut of a printer. The spectral prediction model is also required in inverse mode for the color separation in order to deduce the amounts of inks that are needed to print a specific color.

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“…The average reflectance of the resultant overlay as a function of the halftone area coverages , and the displacements can be obtained as (18) where and are the halftone spots for and , respectively. Though quantitative estimates can be obtained via suitable models for rather general 2-D halftone geometries [40], significant insight can be gained by using a 1-D simplification on this model as shown in Fig. 9(a) that allows us to obtain analytical expressions that characterize the visual detection process.…”

Section: A Halftone Watermarking Using Phase Modulationmentioning

confidence: 99%

Continuous Phase-Modulated Halftones

Oztan

Sharma

2009

IEEE Trans. on Image Process.

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Abstract-A generalization of periodic clustered-dot halftones is proposed, wherein the phase of the halftone spots is modulated using a secondary signal. The process is accomplished by using an analytic halftone threshold function that allows halftones to be generated with controlled phase variation in different regions of the printed page. The method can also be used to modulate the screen frequency, albeit with additional constraints. Visible artifacts are minimized/eliminated by ensuring the continuity of the modulation in phase. Limitations and capabilities of the method are analyzed through a quantitative model. The technique can be exploited for two applications that are presented in this paper: a) embedding watermarks in the halftone image by encoding information in phase or in frequency and b) modulating the screen frequency according to the frequency content of the continuous tone image in order to improve spatial and tonal rendering. Experimental performance is demonstrated for both applications.

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Conditions for Color Misregistration Sensitivity in Clustered-dot Halftones

Cited by 9 publications

References 9 publications

Multiplexed clustered-dot halftone watermarks using bi-directional phase modulation and detection

Multiplexed clustered-dot halftone watermarks using bi-directional phase modulation and detection

Color Reproduction of Metallic-Ink Images

Continuous Phase-Modulated Halftones

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