Frederick Cole Mintzer

Invisible watermarking for image verification

In this paper we propose a new method for invisibly wa- termarking high-quality color and gray-scale images. This method is intended for use in image verification applications to determine whether the content of an image has been altered, due perhaps, to the act of a malicious party. It consists of both a watermarking pro- cess which stamps a watermark into a source image without visual degradation, and a watermark extraction process which extracts a watermark from a stamped image. The extracted watermark can be compared with the embedded watermark to determine whether the image has been altered. The processing used in the watermarking and watermark extraction processes will be presented in this paper. In addition, we shall describe some modifications that provide better security, and an adaptation of the scheme to watermark JPEG im- ages. Experimental results are reported. Some advantages of this technique over other invisible watermarking techniques for verifica- tion will be discussed; these include a high degree of invisibility, color preservation, ease of extraction, and a high degree of protec- tion against the retention of a correct watermark after alteration by a malicious party.

Toward online, worldwide access to Vatican Library materials

The Vatican Library is an extraordinary repository of rare books and manuscripts. Among its 150,000 manuscripts are early copies of works by Aristotle, Dante, Euclid, Homer, and Virgil. Yet today access to the Library is limited. Because of the time and cost required to travel to Rome, only some 2000 scholars can afford to visit the Library each year. Through the Vatican Library Project, we are exploring the practicality of providing digital library services that extend access to portions of the Librarys collections to scholars worldwide, as an early example of providing digital library services that extend and complement traditional library services. A core goal of the project is to provide access via the Internet to some of the Librarys most valuable manuscripts, printed books, and other sources to a scholarly community around the world. A multinational, multidisciplinary team is addressing the technical challenges raised by that goal, including • Development of a multiserver system suitable for providing information to scholars worldwide. • Capture of images of the materials with faithful color and sufficient detail to support scholarly study. Protection of the on-line materials, especially images, from misappropriation. • Development of tools to enable scholars to locate desired materials. • Development of tools to enable scholars to scrutinize images of manuscripts. • In this paper, we provide an overview of the project, a description of the system being developed to satisfy its needs, and a discussion of how the technical challenges are being addressed.

Digital watermarking for high-quality imaging

In this paper, we address the requirements, techniques and applications of digital watermarking for high-quality images. We present several classes of digital watermarking techniques defined by their appearance and application domains, specify the requirements, and summarize the current research efforts in the Image Library Applications group of the IBM Thomas J. Watson Research Center on digital watermarking of high-quality images. We hope that by addressing these issues, we can both provide a foundation for the next generation of digital watermarking techniques, and a vision for their future applications.

Segmentation and automatic descreening of scanned documents

One of the major challenges in scanning and printing documents in a digital library is the preservation of the quality of the documents and in particular of the images they contain. When photographs are offset-printed, the process of screening usually takes place. During screening, a continuous tone image is converted into a bi-level image by applying a screen to replace each color in the original image. When high-resolution scanning of screened images is performed, it is very common in the digital version of the document to observe the screen patterns used during the original printing. In addition, when printing the digital document, more effects tend to appear because printing requires halftoning. In order to automatically suppress these moire patterns, it is necessary to detect the image areas of the document and remove the screen pattern present in those areas. In this paper, we present efficient and robust techniques to segment a grayscale document into halftone image areas, detect the presence and frequency of screen patterns in halftone areas and suppress their detected screens. We present novel techniques to perform fast segmentation based on (alpha) -crossings, detection of screen frequencies using a fast accumulator function and suppression of detected screens by low-pass filtering.

Fragile imperceptible digital watermark with privacy control

We propose a watermarking scheme which allows the watermarked image to be authenticated by an authentication agent without revealing to the authentication agent the human-readable content of the image by combining privacy control with watermarking and authentication mechanisms. This watermarking scheme has universal applicability to data sets such as image, video and audio bit streams. The watermark can be made to be imperceptible to humans. Usage of public key cryptography allows the authentication agent to authenticate without the capabilities to watermark an image.

Automatic visible watermarking of images

Visible image watermarking has become an important and widely used technique to identify ownership and protect copyrights to images. A visible image watermark immediately identifies the owner of an image, and if properly constructed, can deter subsequent unscrupulous use of the image. The insertion of a visible watermark should satisfy two conflicting conditions: the intensity of the watermark should be strong enough to be perceptible, yet it should be light enough to be unobtrusive and not mar the beauty of the original image. Typically such an adjustment is made manually, and human intervention is required to set the intensity of the watermark at the right level. This is fine for a few images, but is unsuitable for a large collection of images. Thus, it is desirable to have a technique to automatically adjust the intensity of the watermark based on some underlying property of each image. This will allow a large number of images to be automatically watermarked, this increasing the throughput of the watermarking stage. In this paper we show that the measurement of image texture can be successfully used to automate the adjustment of watermark intensity. A linear regression model is used to predict subjective assessments of correct watermark intensity based on image texture measurements.

Application of invisible image watermarks to produce remotely printed, duplication-resistant, and demonstrably authentic documents

A secure Internet infrastructure and IBM image watermarking technology have been integrated for the production and authentication of duplication-resistant hard copy documents that may be transmitted to remote sites before being printed. Envisioned applications include the issuance of certificates, contracts, public records, receipts, coupons, ...even college transcripts.

Evolution of a high-quality digital imaging system

A digital imaging system that produces high image quality is not created by inspirational design alone, but evolves over time as the challenges posed by new applications are met. Our experience over the last ten years have led to a versatile high quality imaging systems. In this talk, we will describe some of the system challenges encountered and the enhancements incorporated to address them.

Application of blurring filters to improve detection of invisible image watermarks

Earlier, we presented a highly robust invisible watermarking method having a payload of one bit -- indicating the presence or absence of the watermark. Other invisible watermarking methods also possess this property. Our method, by design, places a major portion of the scant energy of the watermark into the low spatial frequencies of the watermarked image while leaving the higher spatial frequencies, contributed by the original image, largely unaltered. In this paper we will show that application of blurring filters to a presumed watermarked image before attempting watermark detection can improve the probability of detection. Blurring filters, because they suppress high spatial frequencies, are generally quite destructive of image quality. However, for a watermark which has dominant low frequency content, the application of a blurring filter can serve to improve the statistical environment for watermark detection and thereby improves detection probability. This is especially true for detections attempted from scans of printed images. The halftone screening process used in preparing images for printing adds significant high frequency noise to the printed image, and that noise is detrimental to watermark detection. Application of a rudimental blurring filter to a watermarked image before detection will be demonstrated showing that increased amounts of blurring improve the probability of watermark detection. However, the amount of blurring can not be increased without limit, and the amount of beneficial blurring will be shown to be related to the amount of low-pass filtering used in constructing the watermark.

Implementation of a color calibration method for liquid crystal displays

In this paper, we describe the implementation of a color calibration method for LCDs where we assume that the angle of vision is normal to the center of the screen. We change the procedure generally used with cathode ray tubes and take into account the high intensity black of an LCD, the variable chromaticities of its primaries and the less than perfect additivity of its colors. This is done by modifying the calibration data and using correction tables. We describe three rendering algorithms which can be used with this implementation. We test them on four IBM LCD models produced in the last four years and conclude that the simplest algorithm is adequate for the latest model.