Maria V. Ortiz Segovia

Printer and scanner forensics

Contrary to popular opinion, the use of paper in our society will not disappear during the foreseeable future. In fact, paper use continues to grow rather than decline. It is certainly true that as individuals, we may be printing less than we used to. And the role of paper has been transformed from the archival record of a document to a convenient and aesthetically appealing graphical user interface. The use of paper is now intimately linked to the electronic systems that capture, process, transmit, generate, and reproduce textual and graphic content. Paper can be thought of as an interface between humans and the digital world. If this interface is not secure, the entire system becomes vulnerable to attack and abuse. Although paper is read by humans in the same way that it has been for millennia and has had the same fundamental form and composition for almost that long, the technologies for printing and scanning documents and capturing their content have evolved tremendously, especially during the last 20 years. This has moved the capability to generate printed documents from the hands of a select few to anyone with access to low-cost scanners, printers, and personal computers. It has greatly broadened the opportunities for abuse of trust through the generation of fallacious documents and the tampering with existing documents, including the embedding of messages in these documents.

Printer and Scanner Forensics: Models and Methods

Contrary to popular opinion, the use of paper in our society will not disappear any time during the foreseeable future. In fact, the use of paper continues to grow rather than decline. It is certainly true that as individuals, we may be printing less than we used to. And the role of paper has been transformed from the archival record of a document to a convenient and aesthetically appealing graphical user interface. The use of paper is now intimately linked to the electronic systems that capture, process, transmit, generate, and reproduce textual and graphical content. Paper can be thought of as an interface between humans and the digital world. If this interface is not secure, the entire system becomes vulnerable to attack and abuse. Although paper is read by humans in the same way that it has been for millennia, and has had the same fundamental form and composition for almost that long as well, the technologies for printing and scanning documents and capturing their content have evolved tremendously, especially during the last twenty years. This has moved the capability to generate printed documents from the hands of a select few to anyone with access to lowcost scanners, printers, and personal computers. It has greatly broadened the opportunities for abuse of trust through the generation of fallacious documents and tampering with existing documents, including the embedding of messages in these documents.

Printing gloss effects in a 2.5D system

An important aspect for print quality assessment is the perceived gloss level across the printout. There exists a strong relationship between the surface roughness of a printout and the amount of specular reflection which is perceived as gloss variations. Different print parameters influence the surface roughness of the printouts such as the paper substrate, the type of inks and the print method. The lack of control over the print’s surface roughness may result in artefacts such as bronzing and differential gloss. Employing a 2.5D or relief printing system, we are able to control the printout roughness by manipulating the way the ink is deposited in a layer-by-layer basis. By changing the deposition time in between two layers of white ink and the order on which the pixels are printed, we achieve different gloss levels from a matte to a glossy appearance that can be controlled locally. Understanding the relationship between different printing parameters and the resulting gloss level allows us: to solve differential gloss artefacts (to obtain a print with a full gloss or matte finish) and to use the local gloss variations to create reflection effects in the printouts. Applications related to security printing have also been explored. Our results showed a reduced level of gloss toward a matte appearance as the ink deposition time between the layers was increased, allowing more time for the ink to dry between passes. We measured the gloss levels using a gloss meter and a psychophysical experiment was conducted to validate our measurements and observations.

Ink-saving strategy based on document content characterization and halftone textures

Common ink-saving techniques usually restrict the ink consumption when printing a document by replacing a percentage of cyan, magenta, and yellow, by black ink. Even though such methods achieve a considerable reduction in the amount of ink used in a page, the visual quality of the print is affected and unpleasing effects in pastels and skin tones are observed. On the other hand, the quality of the print is not only affected by the ink-saving algorithm, but also by the way the color halftoning algorithm arranges the dots in the print. Therefore, the relationship between the contents of the document to be printed and the printing process needs to be addressed by the ink-saving strategy. A color direct binary search halftoning method that strives to minimize both the ink usage and the perceived error between the continuous-tone color image and the color halftone image is proposed. Our goals are to estimate the effects of the ink-saving module of a printing workflow in individual regions of the document, and to determine the dot arrangement and ink combination that consumes the least amount of ink while preserving printing quality.

An investigation of document aesthetics for web-to-print repurposing of small-medium business marketing collateral

Businesses have traditionally relied on different types of media to communicate with existing and potential customers. With the emergence of the Web, the relation between the use of print and electronic media has continually evolved. In this paper, we investigate one possible scenario that combines the use of the Web and print. Specifically, we consider the scenario where a small- or medium-sized business (SMB) has an existing web site from which they wish to pull content to create a print piece. Our assumption is that the web site was developed by a professional designer, working in conjunction with the business owner or marketing team, and that it contains a rich assembly of content that is presented in an aesthetically pleasing manner. Our goal is to understand the process that a designer would follow to create an effective and aesthetically pleasing print piece. We are particularly interested to understand the choices made by the designer with respect to placement and size of the text and graphic elements on the page. Toward this end, we conducted an experiment in which professional designers worked with SMBs to create print pieces from their respective web pages. In this paper, we report our findings from this experiment, and examine the underlying conclusions regarding the resulting document aesthetics in the context of the existing design, and engineering and computer science literatures that address this topic

Using forms for information hiding and coding in electrophotographic documents

Common forensics tasks such as verifying ownership, authenticity, and copyright of a document can be accomplished through the use of imperceptible marks or signatures inserted during the printing process. Prior research has investigated techniques to embed and recover extrinsic information from electrophotographic text documents and halftone images. But in the absence of suitable halftone patches or text characters, another strategy to embed signatures in the document is needed. In this study, the use of the frames or borders that surround the contents of security documents such as bank statements, event tickets and boarding passes is proposed. While this new embedding context broadens the embedding domain, it also offers the possibility of using error-correcting coding techniques from the area of communications. Experimental results show that the addition of coding methods to the embedding scheme improve the embedding capacity and provide more robustness to our system.

A survey of 3D image quality metrics for relief print evaluation

This paper aims to give a survey of research related to the assessment of image quality metrics of 2.5D and 3D prints. Future research will focus on the ability of combining relief and glossiness in printouts created by a prototype printer that uses multiple layers of ink and varnish. Reproducing these relief or 2.5D surfaces brings out the challenge of evaluating the quality of the outcome. Although, for some decades, active research has been done on 2D image quality assessment, quality evaluation of images in a higher dimension is yet in an early stage. Currently, there are no image quality metrics defined for relief prints and much about their perception is still unknown. As a first step to come up with such metrics, the following survey explores research on the quality assessment of 3D prints, objects, computer simulations and television to relate to future image quality metrics for relief prints.

Aesthetic role of transparency and layering in the creation of photo layouts

Even though technology has allowed us to measure many different aspects of images, it is still a challenge to objectively measure their aesthetic appeal. A more complex challenge is presented when an arrangement of images is to be analyzed, such as in a photo-book page. Several approaches have been proposed to measure the appeal of a document layout that, in general, make use of geometric features such as the position and size of a single object relative to the overall layout. Fewer efforts have been made to include in a metric the influence of the content and composition of images in the layout. Many of the aesthetic characteristics that graphic designers and artists use in their daily work have been either left out of the analysis or only roughly approximated in an effort to materialize the concepts. Moreover, graphic design tools such as transparency and layering play an important role in the professional creation of layouts for documents such as posters and flyers. The main goal of our study is to apply similar techniques within an automated photo-layout generation tool. Among other design techniques, the tool makes use of layering and transparency in the layout to produce a professional-looking arrangement of the pictures. Two series of experiments with people from different levels of expertise with graphic design provided us with the tools to make the results of our system more appealing. In this paper, we discuss the results of our experiments in the context of distinct graphic design concepts.

Towards gloss control in fine art reproduction

The studies regarding fine art reproduction mainly focus on the accuracy of colour and the recreation of surface texture properties. Since reflection properties other than colour are neglected, important details of the artwork are lost. For instance, gloss properties, often characteristic to painters and particular movements in the history of art, are not well reproduced. The inadequate reproduction of the different gloss levels of a piece of fine art leads to a specular reflection mismatch in printed copies with respect to the original works that affects the perceptual quality of the printout. We used different print parameters of a 3D high resolution printing setup to control the gloss level on a printout locally. Our method can be used to control gloss automatically and in crucial applications such as fine art reproduction.

Controlling colour-printed gloss by varnish-halftones

Printing appearance effects beyond colour - such as gloss - is an active research topic in the scope of multi-layer printing (2.5D or 3D printing). Such techniques may enable a perceptually more accurate reproduction of optical material properties and are required to avoid appearance related artefacts sometimes observed in regular colour printing - such as bronzing and differential gloss. In addition to technical challenges of printing such effects, a perceptual space that describes the related visual attributes is crucial; particularly to define perceptually meaningful tolerances and for appearance gamut mapping. In this paper, we focus on spatially-varying gloss created by varnish-halftones. This enables us to print specular gloss effects covering a large portion of the NCS gloss scale from full matte to high gloss. We then conduct a psychophysical experiment to find the relationship between measured specular gloss and a perceptually uniform gloss scale. Our results show that this relationship can be well described by a power function according to Stevens Power Law.