GIF Images Research Articles

Evaluation of pixel-based steganography and stegodetection methods

Steganography is a process that involves hiding a message in an appropriate carrier, for example an image or an audio file. The carrier can then be sent to a receiver without anyone else knowing that it contains a hidden message. This is a process which can be used, for example, by civil rights organizations in repressive states to communicate their message to the outside world without their own government's being aware of it. Less virtuously, it can be used by terrorists to communicate with one another without other people's knowledge. In both cases, the objective is not to make it difficult to read the message as cryptography does, but to hide the existence of the message in the first place, possibly to protect the courier. The aim of this study was to investigate, implement and evaluate a number of common methods of pixel-based steganography. The strengths and weaknesses of the chosen methods were analysed. To provide a common frame of reference, all the steganography methods implemented and analysed worked with GIF images. Eight steganography methods were implemented. The methods were chosen for their different strengths in terms of resistance to different types of steganalysis or their ability to maximize the size of the message they could store. All the methods used were based on the manipulation of the least significant bits of pixel values or the rearrangement of colours to create least significant bit(s) or parity patterns, which correspond to the message being hidden.

Packing Digraphs with Directed Closed Trails

It has been shown [2] that if n is odd and m1,…,mt are integers with mig3 and ∑i=1t mi=vE(Kn)v then Kn can be decomposed as an edge-disjoint union of closed trails of lengths m1,…,mt. This result was later generalized [3] to all sufficiently dense Eulerian graphs G in place of Kn. In this article we consider the corresponding questions for directed graphs. We show that the complete directed graph ****gif image here**** can be decomposed as an edge-disjoint union of directed closed trails of lengths m1,…,mt whenever mig2 and ****gif image here****, except for the single case when n=6 and all mi=3. We also show that sufficiently dense Eulerian digraphs can be decomposed in a similar manner, and we prove corresponding results for (undirected) complete multigraphs.

The visualisation of chemical processes for electronic publishing and presentations

P. W. May, PhysChemComm, 2001, 4, 78 DOI: 10.1039/B103982M

Designing an interactive Web tutorial with cross‐browser dynamic HTML

Texas AM dragging objects; and windows‐style drop‐down menus. It also integrates interactive forms, common gateway interface (CGI), frames, and animated GIF images in the design of the WBT. After describing the design and implementation of the tutorial project, an evaluation of usage statistics and user feedback was conducted, as well as an assessment of its strengths and weaknesses, and a comparison of this tutorial with other common types of training methods. The present article describes an innovative approach for CD‐ROM training using advanced Web technologies such as dynamic HTML, which can simulate and demonstrate the interactive use of the CD‐ROM, as well as the actual search process of a database.

Animations for teaching more advanced acoustics topics

Computers and the World Wide Web are quickly replacing traditional methods of presenting animations of acoustic-wave phenomena in the classroom. A previous paper [V. W. Sparrow and D. A. Russell, J. Acoust. Soc. Am. 103, 2987 (1998)] outlined how mathematica could be used to generate animations which can be converted to quicktime movies or animated GIF images for insertion into HTML documents. The mathematical prowess of a program like mathematica allows for animating more complex wave phenomena while ensuring that the physics and mathematics are correct. At the same time, primitive graphical capabilities allow for visually pleasing results. This paper is an extension of previous work and will include a gallery of new animations which have been used in a senior-level acoustics course for engineering and physics majors. Animations will include some theoretical (sound fields of complex sources, particle motion in waves, and multiple-dof vibrating systems) as well as some experimental (modes of vibration of acoustic and electric guitars) animations. Some hints of mathematica tricks to generate animations will be shared, as well as methods for producing animated GIF files.

MED11/373: Intranet-/Internet Software for Preparation and Presentation of Lectures in Dermatology

IntroductionA software package consisting of a semantic network and co-operating Java applications was created for supporting lectures in dermatology or other visually oriented medical disciplines. This work is based on the SENTIMED-project (SEmantic Net Toolbox for Images in Medical EDucation) of the Department of Dermatology and the Chair for Computer Science II, University of Würzburg. SENTIMED is part of the Bavarian government initiative "Multimedia in Education".MethodsThe first building block of the package is a digital image archive in SENTIMED which consists of over 4000 high resolution slides. Three sizes thereof (up to 1024x768 pixels) are stored on a CD-ROM together with the semantic network for navigation and a set of Java applications for image retrieval and manipulation. The highest resolution formats (3072x2048 pixels) are available from a server in the intranet. The automated installation on a stand-alone/intranet PC requires 30 MB of disk space. The CD-ROM contents is protected against unauthorized access and copying by either a local or a network-dongle, i.e. one in the local parallel port of the stand-alone PC or one in the intranet-server which the other PCs use via the clinic network.ResultsThe semantic network can be presented and explored by a standard WWW Browser. It consists of an XML database, program-generated HTML pages, CGI scripts and Java applets. Entry points to the network are several alphabetical and hierarchical lists of e.g. diagnoses or skin regions. Context-sensitive links to external sources like PubMed or RxList give a comfortable access to internet-resources for further information-retrieval. Within a separate Java application lecturers can search the archive for collections of images with specified criteria (diagnoses, ICD code, localisation, etc.). Images can be compared, copied into intermediate repositories and finally ordered for the presentation. Powerpoint slides can be imported as well as any other JPEG and GIF images. Regions of interest in the pictures are marked to supply high resolution zooms from the image archive. These regions are then extracted from the original on the server and transferred via Intranet. The presentation tool offers features like an index page for all slides (a tableau of thumbnail formats), zooming of predefined areas by loading parts in higher resolution or ad-hoc by calculated zooms of any rectangular area from the image. The lecture is presented with a high resolution multimedia projector.DiscussionOn top of a digital image archive a set of Java routines efficiently supports lecturers in dermatology to prepare and present lectures or conference contributions. The semantic network layer guides the fast retrieval of images and related information in the context of an Intranet/Internet.

Network-conscious GIF image transmission over the Internet

Traditional image compression techniques seek the smallest possible file size for a given level of image quality. By contrast, network-conscious image compression techniques take into account the fact that a compressed image will be transmitted over a packet-switched network that may lose and reorder packets. We describe GIFNCa, a network-conscious revision of the popular GIF89a standard. As with GIF89a, GIFNCa compresses an image using LZW encoding, however GIFNCa does so using an Application Level Framing approach. The data is segmented into path MTU-size data units, each of which can be independently decompressed and displayed on its own. Under lossy network conditions, when used in combination with an unordered transport protocol, GIFNCa permits faster progressive display at the receiver than GIF89a over an ordered transport protocol. This advantage comes in exchange for a small penalty in overall compression. This paper defines GIFNCa, and presents preliminary experimental data concerning this tradeoff. The overall goal of this research is to illustrate (1) the value of considering network characteristics in designing image formats, and (2) the value of unordered transport service.

Online access to weather satellite imagery through the World Wide Web

Both global area coverage (GAC) and high-resolution picture transmission (HRPT) data from the Advanced Very High Resolution Radiometer (AVHRR) are made available to Internet users through an online data access system. Older GOES-7 data are also available. Created as a data system for NASA's future Earth Observing System Data and Information System (EOSDIS), this testbed provides an opportunity to test both the technical requirements of an online data system and the different ways in which the general user community would employ such a system. Initiated in December 1991, the basic data system experienced five major evolutionary changes in response to user requests and requirements. Features added with these changes were the addition of online browse, user subsetting, dynamic image processing/navigation, a stand-alone data storage system, and movement from an X-windows graphical user interface (GUI) to a World Wide Web (WWW) interface. Over its lifetime, the system has had as many as 2500 registered users. The system on the WWW has had over 2500 hits since October 1995. Many of these hits are by casual users that only take the GIF images directly from the interface screens and do not specifically order digital data. Still, there is a consistent stream of users ordering the navigated image data and related products (maps and so forth). The authors have recently added a real-time, seven-day, northwestern United States normalized difference vegetation index (NDVI) composite that has generated considerable interest.

Hypermedia presentation and authoring system

This paper describes the Hypermedia Presentation and Authoring System (HPAS), a Web browser with built-in authoring capabilities. In contrast to traditional browsers, it manages time-based hypermedia presentations and the associated dynamic spatial layout with respect to time. The system manipulates various media types by embedding object presenters, editors, and converters, which combine to provide transparent operations on hypermedia objects, such as MPEG videos, GIF images, rich text files, etc.

The Butcher-Oemler Effect at Low Redshift: Spectroscopy of Five Nearby Clusters of Galaxies

view Abstract Citations (134) References (65) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Butcher-Oemler Effect at Low Redshift: Spectroscopy of Five Nearby Clusters of Galaxies Caldwell, Nelson ; Rose, James A. Abstract We present multi-fiber spectroscopy and broadband imaging of early-type galaxies in five nearby rich clusters of galaxies. The main purpose was to look for "abnormal" spectrum galaxies (i.e., post-starburst galaxies which have strong Balmer absorption lines and emission line galaxies) in nearby clusters that are similar to those found by Caldwell et al. [AJ, 106, 473 (1993)] in the Coma cluster. Three of the clusters were purposefully selected to have pronounced double structure in their spatial distribution of the galaxies. Our primary conclusion is that ∼15% of the early-type galaxies in these nearby rich clusters have signs of ongoing or recent star formation. Furthermore, the starburst and post-starburst nature of these abnormal spectra is reminiscent of that seen in distant clusters, although at a reduced frequency and burst strength. Thus activity similar to that seen in distant clusters is still ongoing, at a reduced level, in present-epoch rich clusters. The frequency of such galaxies appears to be enhanced significantly over that seen in field galaxies. Most of the new post-starburst galaxies are disk galaxies; three E galaxies in one cluster and one in another cluster have current star formation. We also find evidence in the spatial and kinematic structure of several of the clusters that subclusters have recently passed through the main clusters and are now emerging out the other side. This inference is based on a comparison of the spatial and kinematic cluster data with N-body simulations of infalling clusters. Specifically, we see evidence of velocity gradients and/or a dispersed appearance of the observed subclusters, both of which are produced by tidal distension and disruption of infalling subclusters. If, as we suspect, the subclusters passed through the main clusters more than a Gyr ago, then the post-starburst time scales of 1 Gyr imply that the star formation bursts are only triggered during (or after) the subcluster passage through the center of the main cluster. We speculate that shocks induced in the collisions of the cluster and subcluster ICMs may trigger the galaxy starbursts. Publication: The Astronomical Journal Pub Date: February 1997 DOI: 10.1086/118271 arXiv: arXiv:astro-ph/9611001 Bibcode: 1997AJ....113..492C Keywords: GALAXIES: EARLY-TYPE; GALAXIES: STELLAR CONTENT; STARS: FORMATION; GALAXIES: STARBURST; GALAXIES: INTERACTIONS; Astrophysics E-Print: To appear in the Astronomical Journal. 68 pages including 24 pages of figures. To include the gif images of Fig 12 in postscript form, use xv to change gif to ps with names as given in the tex file, and uncomment the appropriate lines in the figure caption area of tex file full text sources arXiv | ADS | data products SIMBAD (318) NED (314)

Transcoding GIF images to JPEG-LS

We investigate transcoding of GIF images to JPEG-LS, the new lossless image compression standard. A straight forward conversion can lead to file sizes that are significantly larger than the size of the corresponding GIF file. We show that suitable reordering of the color table leads to file sizes significantly smaller than those required by the GIF format.

Let's all go to the movies

Let's all go to the movies