Spatially Varying Gray Component Replacement To Watermark Printed Images

We present a method to include watermarks in printed images. It does not degrade textures and has a high information channel capacity. With accurate printer calibration, in theory, the same color under different gray component replacement strategies (GCR) should look the same, under specific viewing conditions. We spatially vary the GCR along the image in a manner that is not perceptible, and we emply an estimation method to detect such changes. The choice of GCR for a given region comprises an additional information channel that embeds a watermark or hidden information. The challenge is how to detect which GCR was used and that is the focus of this paper. For that, we estimate the RGB value of each pixel and the CMYK values intended to be put onto the paper, by scanning the printed page. With that information, we can estimate which GCR strategy was used in a given region and retrieve the watermark message. Instead of focusing on a particular watermarking scheme, we are only concerned with the practical aspects of producing a spatially varying GCR and of robustly estimating which GCR strategy was used at a region. Excellent results are shown which demonstrate the potential of the method. Spatially Varying Gray Component Replacement To Watermark Printed Images Ricardo de Queiroz, Karen Braun and Robert Loce Abstract – We present a method to include watermarks in printed images. It We present a method to include watermarks in printed images. It does not degrade textures and has a high information channel capacity. With accurate printer calibration, in theory, the same color under different gray component replacement strategies (GCR) should look the same, under specific viewing conditions. We spatially vary the GCR along the image in a manner that is not perceptible, and we emply an estimation method to detect such changes. The choice of GCR for a given region comprises an additional information channel that embeds a watermark or hidden information. The challenge is how to detect which GCR was used and that is the focus of this paper. For that, we estimate the RGB value of each pixel and the CMYK values intended to be put onto the paper, by scanning the printed page. With that information, we can estimate which GCR strategy was used in a given region and retrieve the watermark message. Instead of focusing on a particular watermarking scheme, we are only concerned with the practical aspects of producing a spatially varying GCR and of robustly estimating which GCR strategy was used at a region. Excellent results are shown which demonstrate the potential of the method.