It is argued that, hidden within the flow of signals from typical cameras, through image processing, to display media, is a homomorphic filter. While homomorphic filtering is often desirable, there are some occasions where it is not. Thus, cancellation of this implicit homomorphic filter is proposed, through the introduction of an antihomomorphic filter. This concept gives rise to the principle of quantigraphic image processing, wherein it is argued that most cameras can be modeled as an array of idealized light meters each linearly responsive to a semi-monotonic function of the quantity of light received, integrated over a fixed spectral response profile. This quantity is neither radiometric nor photometric, but, rather, depends only on the spectral response of the sensor elements in the camera. A particular class of functional equations, called comparametric equations, is introduced as a basis for quantigraphic image processing. Comparametric equations are fundamental to the analysis and processing of multiple images differing only in exposure. The well-known "gamma correction" of an image is presented as a simple example of a comparametric equation, for which it is shown that the underlying quantigraphic function does not pass through the origin. For this reason it is argued that exposure adjustment by gamma correction is inherently flawed, and alternatives are provided. These alternatives, when applied to a plurality of images that differ only in exposure, give rise to a new kind of processing in the "amplitude domain" (as opposed to the time domain or the frequency domain). While the theoretical framework presented in this paper originated within the field of wearable cybernetics (wearable photographic apparatus) in the 1970s and early 1980s, it is applicable to th...

In recent years, access to multimedia data has become much easier due to the rapid growth of the Internet. While this is usually considered an improvement of everyday life, it also makes unauthorized copying and distributing of multimedia data much easier, therefore presenting a challenge in the field of copyright protection. Digital watermarking, which is inserting copyright information into the data, has been proposed to solve the problem. In this paper, we first discuss the features that a practical digital watermarking system for ownership verification requires. Besides perceptual invisibility and robustness, we claim that the private control of the watermark is also very important. Second, we present a novel wavelet-based watermarking algorithm. Experimental results and analyses are then given to demonstrate that the proposed algorithm is effective and can be used in a practical system.

Current portable computers and PDAs fail to truly become part of our daily lives in the sense that we need to stop what we are doing and expend conscious effort to use them. They also do not have the situational awareness that they should have: while they are not being explicitly used, they are unable to remain attentive to possible ways to help the user. Environmental technology in the form of ubiquitous computing, ubiquitous surveillance, and smart spaces, has attempted to bring multimedia computing seamlessly into our daily lives, promising a future world with cameras and microphones everywhere, connected to invisible computing, always attentive to our every movement or conversation. This raises some serious privacy issues. Even if we ignore these issues, there is still a problem of user-control, customization, and reliance on an infrastructure that will not (and probably should not) become totally ubiquitous. In response to these problems, a personal, wearable, multimedia computer,...

Consider a static scene and fixed center of projection, about which a camera is free to zoom, pan, tilt, and rotate about its optical axis. With an ideal camera, the resulting images are in the same orbit of the projective group-action, and each pixel of each image provides a measurement of a ray of light passing through a common point in space. Unfortunately, most modern cameras have a built in automatic gain control (AGC), automatic shutter, or auto-iris, which, in many cases cannot be turned off. Many modern digitizers to which cameras are connected have their own AGC which also cannot be disabled. With AGC, the characteristic response function of the camera varies, making it impossible to accurately describe one image as a projective coordinate transformed version of another. This paper proposes not only a solution to this problem, but a means of turning AGC into an asset, so that even in cases where AGC could be disabled, pencigraphers of the future will be turning AGC on. 1 INTR...

In this paper we present a novel way of creating mosaics from an MPEG video sequence. Two original aspects of our work are that (1) we explicitly compute camera motion between frames and (2) we deduce the camera motion directly from the motion vectors encoded in the MPEG video stream. This enables us to create mosaics more simply and quickly than with other methods.

This paper describes an approach whereby comparametric analysis is used in jointly registering image pairs in their domain and range, i.e., in their spatial coordinates and pixel values, respectively. This is accomplished by approximating a camera's nonlinear comparametric function with a constrained piecewise linear one. The optimal fitting of this approximation to comparagram data is then used in a re-parameterized version of the camera's comparametric function to estimate the exposure difference between images. Doing this allows the inherently nonlinear problem of joint domain and range registration to be performed using a computationally attractive least squares formalism. The paper first presents the range registration process and then describes the strategy for performing the joint registration. The models used allow for the pair-wise registration of images taken from a camera that can automatically adjust its exposure as well as tilt, pan, rotate and zoom about its optical center. Results concerning the joint registration as well as range-only registration are provided to demonstrate the method's effectiveness.

We are investigating applications in which a field worker, equipped with a wearable computer, is networked wirelessly with a remote expert. In this paper, we present a simple and robust augmented reality registration algorithm that can be used to lock annotations given by the remote expert onto parts of the scene viewed by the field worker through a head mounted see-through display. The algorithm can also be used to construct an image mosaic interface for the remote expert to place annotations regardless of the current viewpoint of the field worker. We also present a networkable desktop-based augmented reality prototype system to test the registration algorithm. A manual recalibration user interface is implemented to deal with registration errors. 1: Introduction Wearable computers provide users with timely and relevant information based on active sensing of the current surrounding environment (see Figure 1). Timeliness is achieved by having the wearable computer "always on" [14], an...

A novel unsupervised video object segmentation algorithm is presented, aiming to segment a video sequence to objects: spatiotemporal regions representing a meaningful part of the sequence. The proposed algorithm consists of three stages: initial segmentation of the first frame using color, motion, and position information, based on a variant of the K-Means-with-connectivity -constraint algorithm; a temporal tracking algorithm, using a Bayes classifier and rule-based processing to reassign changed pixels to existing regions and to efficiently handle the introduction of new regions; and a trajectory-based region merging procedure that employs the long-term trajectory of regions, rather than the motion at the frame level, so as to group them to objects with different motion. As shown by experimental evaluation, this scheme can efficiently segment video sequences with fast moving or newly appearing objects. A comparison with other methods shows segmentation results corresponding more accurately to the real objects appearing on the image sequence.

We are entering a pivotal era in which we will become inextricably intertwined with computational technology that will become part of our everyday lives in a much more immediate and intimate way than in the past. The recent explosion of interest in so-called "wearable computers" is indicative of this general trend. The purpose of this paper is to provide an historical account of my wearable computer effort, from the 1970s (WearComp0) to present (WearComp7), with emphasis on a particular variation whose origins were in imaging applications. This application, known as `personal imaging', originated as a computerized photographer's assistant which I developed for what many regarded as an obscure photographic technique. However, it later evolved into a more diverse apparatus and methodology, combining machine vision and computer graphics, in a wearable tetherless apparatus, useful in day-to-day living. Personal imaging, at the intersection of art, science, and technology, has given rise t...

Storyboarding is a standard method for visual summarization of shots in film and video preproduction. Reverse storyboarding is the generation of similar visualizations from existing footage. We identify the key attributes of preproduction storyboards then develop computational techniques that extract corresponding features from video, render them appropriately, then composite them into a single storyboard image. The result succinctly represents background composition, foreground object appearance and motion, and camera motion. For tracking shots, we show that the visual representation conveys all the essential elements of shot composition. 1