Lawrence O'Gorman

The document spectrum for page layout analysis

Page layout analysis is a document processing technique used to determine the format of a page. This paper describes the document spectrum (or docstrum), which is a method for structural page layout analysis based on bottom-up, nearest-neighbor clustering of page components. The method yields an accurate measure of skew, within-line, and between-line spacings and locates text lines and text blocks. It is advantageous over many other methods in three main ways: independence from skew angle, independence from different text spacings, and the ability to process local regions of different text orientations within the same image. Results of the method shown for several different page formats and for randomly oriented subpages on the same image illustrate the versatility of the method. We also discuss the differences, advantages, and disadvantages of the docstrum with respect to other lay-out methods. >

Electronic marking and identification techniques to discourage document copying

Modern computer networks make it possible to distribute documents quickly and economically by electronic means rather than by conventional paper means. However, the widespread adoption of electronic distribution of copyrighted material is currently impeded by the ease of unauthorized copying and dissemination. In this paper we propose techniques that discourage unauthorized distribution by embedding each document with a unique codeword. Our encoding techniques are indiscernible by readers, yet enable us to identify the sanctioned recipient of a document by examination of a recovered document. We propose three coding methods, describe one in detail, and present experimental results showing that our identification techniques are highly reliable, even after documents have been photocopied. >

An approach to fingerprint filter design

Abstract A procedure for filter design is described for enhancing fingerprint images. The procedure consists of five main steps: user-specification of appropriate image features, determination of local ridge orientations throughout the image, smoothing of this orientation image, pixel-by-pixel image enhancement by application of oriented, matched filter masks, and post-processing to reduce background and boundary noise. The contribution of this work is to quantify and justify the functional relationships between image features and filter parameters so that the design process can be easily modified for different conditions of noise and scale. Application of the filter shows good ridge separation and continuity, and background noise reduction.

Document marking and identification using both line and word shifting

Continues a study of document marking to deter illicit dissemination. An experiment performed reveals that the distortion on the photocopy of a document is very different in the vertical and horizontal directions. This leads to the strategy that marks a text line both vertically using line shifting and horizontally using word shifting. A line that is marked is always accompanied by two unmarked control lines one above and one below. They are used to measure distortions in the vertical and horizontal directions in order to decide whether line or word shift should be detected. Line shifts are detected using a centroid method that bases its decision on the relative distance of line centroids. Word shifts are detected using a correlation method that treats a profile as a waveform and decides whether it originated from a waveform whose middle block has been shifted left or right. The maximum likelihood detectors for both methods are given.

Binarization and multithresholding of document images using connectivity

Abstract Thresholding is a common image processing operation applied to gray-scale images to obtain binary or multilevel images. Traditionally, one of two approaches is used: global or locally adaptive processing. However, each of these approaches has a disadvantage: the global approach neglects local information, and the locally adaptive approach neglects global information. A thresholding method is described here that is global in approach, but uses a measure of local information, namely connectivity. Thresholds are found at the intensity levels that best preserve the connectivity of regions within the image. Thus, this method has advantages of both global and locally adaptive approaches. This method is applied here to document images. Experimental comparisons against other thresholding methods show that the connectivity-preserving method yields much improved results. On binary images, this method has been shown to improve subsequent OCR recognition rates from about 95% to 97,5%. More importantly, the new method has been shown to reduce the number of binarization failures (where text is so poorly binarized as to be totally unrecognizable by a commercial OCR system) from 33% to 6% on difficult images. For multilevel document images, as well, the results show similar improvement.

The RightPages image-based electronic library for alerting and browsing

The RightPages electronic library prototype system, which gives users full online library services, is described. The prototype takes advantage of fast hardware, multimedia workstations, and broadband networks to process scientific and technical journals for users and to offer a service that: alerts them to the arrival of new journal articles matching their interest profiles; lets them immediately examine images of pages in the alerted articles and browse through other articles in the database; and enables them to order paper copies of any articles in the database. The system runs on a local area network that connects one or more scanning stations, a centralized document database server and multiple user stations running X Windows servers. The RightPages interface runs as an X Windows application on Sun workstations or X terminals. The systems image and document processing, including noise reduction, document layout analysis, text processing, and display processing are discussed.<<ETX>>

Protecting ownership rights through digital watermarking

The Internet revolution is now in full swing, and commercial interests abound. As with other maturing media technologies, the focus is moving from technology to content, as commercial vendors and developers try to use network technology to deliver media products for profit. This shift inevitably raises questions about how to protect ownership rights. Digital watermarking has been proposed as a way to identify the source, creator, owner, distributor, or authorized consumer of a document or image. Its objective is to permanently and unalterably mark the image so that the credit or assignment is beyond dispute. In the event of illicit use, the watermark would facilitate the claim of ownership, the receipt of copyright revenues, or successful prosecution. Watermarking has also been proposed for tracing images that have been illicitly redistributed. In the past, the infeasibility of large-scale photocopying and distribution often limited copyright infringement, but modern digital networks make large-scale dissemination simple and inexpensive. Digital watermarking allows each image to be uniquely marked for every buyer. If that buyer makes an illicit copy, the copy itself identifies the buyer as the source.

Image and document processing techniques for the RightPages electronic library system

Describes some of the document processing techniques used in the RightPages electronic library system. Since the system deals with scanned images of document pages, these techniques are critical to the use and appearance of the system. The author describes three techniques: (1) for noise reduction from binary document pages to improve page appearance and subsequent optical character recognition and compression; (2) for subsampling the text image to fit on the computer screen white maintaining readability; and (3) a document layout analysis technique to determine text blocks.<<ETX>>

Innovations in fingerprint capture devices

Abstract The image capture device plays a key role in fingerprint authentication. In recent years, we have seen remarkable innovations in these devices, which have reduced the size, lowered the price, and improved the performance. These new sensors have paved the way for deployment of fingerprint authentication beyond law enforcement applications to more widespread personal authentication. This paper provides an overview of fingerprint capture devices. Sensor issues and future trends are also discussed.

Subpixel registration using a concentric ring fiducial

An examination of the effects of spatial sampling and image noise on the precision with which the centroids of different geometric shapes can be determined is presented. The concentric ring fiducial-a bulls-eye pattern-is identified as having desirable qualities of high location precision and rotational invariance. The performance of the concentric fiducial, as a function of diameter, number of rings. and ring spacing, has been tested, and these results are shown.<<ETX>>