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Proceedings Paper

Watermarking spot colors
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Paper Abstract

Watermarking of printed materials has usually focused on process inks of cyan, magenta, yellow and black (CMYK). In packaging, almost three out of four printed materials include spot colors. Spot colors are special premixed inks, which can be produced in a vibrant range of colors, often outside the CMYK color gamut. In embedding a watermark into printed material, a common approach is to modify the luminance value of each pixel in the image. In the case of process color work pieces, the luminance change can be scaled to the C, M, Y and K channels using a weighting function, to produce the desired change in luminance. In the case of spot color art designs, there is only one channel available and the luminance change is applied to this channel. In this paper we develop a weighting function to embed the watermark signal across the range of different spot colors. This weighting function normalizes visibility effect and signal robustness across a wide range of different spot colors. It normalizes the signal robustness level over the range of an individual spot color’s intensity levels. Further, it takes into account the sensitivity of the capturing device to the different spot colors.

Paper Details

Date Published: 20 June 2003
PDF: 10 pages
Proc. SPIE 5020, Security and Watermarking of Multimedia Contents V, (20 June 2003); doi: 10.1117/12.477305
Show Author Affiliations
Osama M. Alattar, Digimarc Corp. (United States)
Alastair M. Reed, Digimarc Corp. (United States)

Published in SPIE Proceedings Vol. 5020:
Security and Watermarking of Multimedia Contents V
Edward J. Delp III; Ping Wah Wong, Editor(s)

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