Showing papers in "electronic imaging in 2000"
TL;DR: Li et al. as mentioned in this paper proposed a semi-fragile watermarking technique that accepts JPEG lossy compression on the watermarked image to a pre-determined quality factor, and rejects malicious attacks.
Abstract: In this paper, we propose a semi-fragile watermarking technique that accepts JPEG lossy compression on the watermarked image to a pre-determined quality factor, and rejects malicious attacks. The authenticator can identify the positions of corrupted blocks, and recover them with approximation of the original ones. In addition to JPEG compression, adjustments of the brightness of the image within reasonable ranges, are also acceptable using the proposed authenticator. The security of the proposed method is achieved by using the secret block mapping function which controls the signature generating/embedding processes. Our authenticator is based on two invariant properties of DCT coefficients before and after JPEG compressions. They are deterministic so that no probabilistic decision is needed in the system. The first property shows that if we modify a DCT coefficient to an integral multiple of a quantization step, which is larger than the steps used in later JPEG compressions, then this coefficient can be exactly reconstructed after later acceptable JPEG compression. The second one is the invariant relationships between two coefficients in a block pair before and after JPEG compression. Therefore, we can use the second property to generate authentication signature, and use the first property to embed it as watermarks. There is no perceptible degradation between the watermarked image and the original. In additional to authentication signatures, we can also embed the recovery bits for recovering approximate pixel values in corrupted areas. Our authenticator utilizes the compressed bitstream, and thus avoids rounding errors in reconstructing DCT coefficients. Experimental results showed the effectiveness of this system. The system also guaranies no false alarms, i.e., no acceptable JPEG compression is rejected.
258 citations
TL;DR: In this article, the authors proposed an attack based on an estimation of the embedded watermark in the spatial domain through a filtering process, and the estimate of the watermark is then adapted and inserted into the target image.
Abstract: Research in digital watermarking has progressed along two paths. While new watermarking technologies are being developed, some researchers are also investigating different ways of attacking digital watermarks. Common attacks to watermarks usually aim to destroy the embedded watermark or to impair its detection. In this paper we propose a conceptually new attack for digitally watermarked images. The proposed attack does not destroy an embedded watermark, but copies it from one image to a different image. Although this new attack does not destroy a watermark or impair its detection, it creates new challenges, especially when watermarks are used for copyright protection and identification. The process of copying the watermark requires neither algorithmic knowledge of the watermarking technology nor the watermarking key. The attack is based on an estimation of the embedded watermark in the spatial domain through a filtering process. The estimate of the watermark is then adapted and inserted into the target image. To illustrate the performance of the proposed attack we applied it to commercial and non-commercial watermarking schemes. The experiments showed that the attack is very effective in copying a watermark from one image to a different image. In addition, we have a closer look at application dependent implications of this new attack.
237 citations
TL;DR: In this article, a semi-fragile watermark for still images is proposed that can detect information altering transformations even after the watermarked content is subjected to information preserving alterations.
Abstract: Digital watermarking research has generally focused upon two classes of watermarks, fragile and robust. Robust watermarks are designed to be detected even after attempts are made to remove them. Fragile watermarks are used for authentication purposes and are capable of detecting even minute changes of the watermarked content. Unfortunately, neither type of watermark is ideal when considering 'information preserving' transformations (such as compression) which preserve the meaning or expression of the content and 'information altering' transformations (such as feature replacement) which change the expression of the content. In this paper we describe a semi-fragile watermark for still images that can detect information altering transformations even after the watermarked content is subjected to information preserving alterations.
234 citations
TL;DR: In this paper, a review of tone reproduction curves (TRCs) and tone reproduction operators (TROs) is presented, which operate pointwise on the image data, making the algorithms simple and efficient.
Abstract: In this paper, we review several algorithms that have been proposed to transform a high dynamic range image into a reduced dynamic range image that matches the general appearance of the original. We organize these algorithms into two categories: tone reproduction curves (TRCs) and tone reproduction operators (TROs). TRCs operate pointwise on the image data, making the algorithms simple and efficient. TROs use the spatial structure of the image data and attempt to preserve local image contrast.
185 citations
TL;DR: This paper describes a methodology, using a camera simulator and image quality metrics, for determining the optimal pixel size, and it is shown that the optimalpixel size scales with technology, btu at slower rate than the technology itself.
Abstract: Pixel design is a key part of image sensor design. After deciding on pixel architecture, a fundamental tradeoff is made to select pixel size. A small pixel size is desirable because it results in a smaller die size and/or higher spatial resolution; a large pixel size is desirable because it results in higher dynamic range and signal-to-noise ratio. Given these two ways to improve image quality and given a set of process and imaging constraints an optimal pixel size exists. It is difficult, however, to analytically determine the optimal pixel size, because the choice depends on many factors, including the sensor parameters, imaging optics and the human perception of image quality. This paper describes a methodology, using a camera simulator and image quality metrics, for determining the optimal pixel size. The methodology is demonstrated for APS implemented in CMOS processes down to 0.18 (mu) technology. For a typical 0.35 (mu) CMOS technology the optimal pixel size is found to be approximately 6.5 micrometers at fill factor of 30%. It is shown that the optimal pixel size scales with technology, btu at slower rate than the technology itself.
114 citations
TL;DR: In this paper, the authors extend their previous work on robust image digest functions describing ideas how to make the hash function independent of image orientation and size, which can be clearly utilized for other applications, such as a search index for an efficient image database search.
Abstract: Digital watermarks have recently been proposed for authentication and fingerprinting of both video data and still images and for integrity verification of visual multimedia. In such applications, the watermark must be oblivious and has to depend on a secret key and on the original image. It is important that the dependence on the key be sensitive, while the dependence on the image be continuous (robust). Both requirements can be satisfied using special image digest (hash) functions that return the same bit-string for whole class of images derived from an original image using common processing operations including rotation and scaling. It is further required that two completely different images produce completely different bit-strings. In this paper, we extend our previous work on robust image digest functions describing ideas how to make the hash function independent of image orientation and size. The robust image digest can be clearly utilized for other applications, such as a search index for an efficient image database search.© (2000) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
111 citations
TL;DR: The proposed attack is based on a stochastic formulation of the watermark removal problem, considering the embedded watermark as additive noise with some probability distribution, and shows the high efficiency of the proposed attack against known academic and commercial methods.
Abstract: Digital image watermarking has become a popular technique for authentication and copyright protection. For verifying the security and robustness of watermarking algorithms, specific attacks have to be applied to test them. In contrast to the known Stirmark attack, which degrades the quality of the image while destroying the watermark, this paper presents a new approach which is based on the estimation of a watermark and the exploitation of the properties of Human Visual System (HVS). The new attack satisfies two important requirements. First, image quality after the attack as perceived by the HVS is not worse than the quality of the stego image. Secondly, the attack uses all available prior information about the watermark and cover image statistics to perform the best watermark removal or damage. The proposed attack is based on a stochastic formulation of the watermark removal problem, considering the embedded watermark as additive noise with some probability distribution. The attack scheme consists of two main stages: (1) watermark estimation and partial removal by a filtering based on a Maximum a Posteriori (MAP) approach; (2) watermark alteration and hiding through addition of noise to the filtered image, taking into account the statistics of the embedded watermark and exploiting HVS characteristics. Experiments on a number of real world and computer generated images show the high efficiency of the proposed attack against known academic and commercial methods: the watermark is completely destroyed in all tested images without altering the image quality. The approach can be used against watermark embedding schemes that operate either in coordinate domain, or transform domains like Fourier, DCT or wavelet.
110 citations
TL;DR: In this paper, the authors proposed an approximation method that can calculate the Fresnel hologram fast, where an object is assumed as a collection of self-illuminated points and the fringes from each object point are superposed.
Abstract: For practical holographic video system, it is important to generated holographic fringe as fast as possible. We have proposed an approximation method that can calculate the Fresnel hologram fast. To compute the hologram, an object is assumed as a collection of self-illuminated points and the fringes from each object point are superposed. To determine the fringe, a distance between object point and sampling point on the hologram is used to obtain phase of the light. Since sampled hologram usually has small pixel intervals, the difference of the distance values between adjacent pixels is also small and its n-th order difference becomes a constant. Therefore, the distance value at certain pixel can be obtained from the neighbor pixel with simple additions. We have investigated approximation errors and computational speed of the method. The numerical results show that the proposed method is quite effective. The distance error can be reduced less that one wavelength with practical parameters and the computational speed becomes 16 times faster than conventional method. With the proposed method, a hologram, which has horizontal parallax only, 1.3 mega- pixels and 1,000 object points, can be calculated less than on second with a personal computer.
108 citations
TL;DR: Six-primary color display is presented to reproduce the expanded color Gamut, by using two conventional RGB projectors and six interference filters to maximize the volume of the color gamut in CIE-LUV uniform color space.
Abstract: The range of the reproducible color, i.e., color gamut, of the conventional display devices such as CRTs (cathode ray tubes) and LCDs (liquid crystal displays) is sometimes insufficient for reproducing the natural color of an object through color imaging systems. In this paper, six-primary color display is presented to reproduce the expanded color gamut, by using two conventional RGB projectors and six interference filters. The design method of the filters is also introduced to maximize the volume of the color gamut in CIE-LUV uniform color space. Using the experimental system, the gamut of the six-primary projection display is evaluated comparing with that of conventional CRTs and projectors.
99 citations
TL;DR: In this paper, a new generation of smart pixels, so-called lock-in pixels, is introduced, which are capable of measuring phase, amplitude and offset of modulated light up to some tens of MHz, making them ideally suited to be used as receivers in 3D time-of-flight (TOF) distance measurement systems.
Abstract: A new generation of smart pixels, so-called demodulation or lock-in pixels is introduced in this paper. These devices are capable of measuring phase, amplitude and offset of modulated light up to some tens of MHz, making them ideally suited to be used as receivers in 3D time-of-flight (TOF) distance measurement systems. Different architectures of such devices are presented and their specific advantages and disadvantages are discussed. Furthermore, a simple model is introduced giving the shot noise limited range resolution of a range camera working with these demodulation pixels. Finally, a complete TOF range camera based on an array of one of the new lock-in pixels will be described. This TOF- camera uses only standard components and does not need any mechanically scanning parts. With this camera non- cooperative targets can be measured with a few centimeters resolution over a distance of up to 20 meters.
89 citations
TL;DR: This paper presents the use of Digimarc Corporation's watermarking technology to implement Smart Images and presents an application that demonstrates how Smart Images facilitate both traditional and electronic commerce.
Abstract: This paper introduces the concept of Smart Images and explains the use of watermarking technology in their implementation. A Smart Image is a digital or physical image that contains a digital watermark, which leads to further information about the image content via the Internet, communicates ownership rights and the procedure for obtaining usage rights, facilitates commerce, or instructs and controls other computer software or hardware. Thus, Smart Images, empowered by digital watermarking technology, act as active agents or catalysts which gracefully bridge both traditional and modern electronic commerce. This paper presents the use of Digimarc Corporation's watermarking technology to implement Smart Images. The paper presents an application that demonstrates how Smart Images facilitate both traditional and electronic commerce. The paper also analyzes the technological challenges to be faced for ubiquitous use of Smart Images.
TL;DR: The Wong schemes are extended so that the resulting algorithms can resist the VQ attack and at the same time provide the same localization property in the watermark as the original schemes.
Abstract: In previous work, Wong had proposed both secret key and public key watermarking schemes for image authentication that can detect and localized any change made to a watermarked image. The techniques proposed were block-based, that is, they partitioned the image into non-overlapping blocks and separately authenticated each block. Subsequently, Holliman and Memon observed that many block based watermarking schemes are vulnerable to substitution attacks. They specifically showed that the Wong schemes can be attacked using a 'vector quantization' (VQ) approach. This attack exploits that fact that if a sufficient number of images containing the same watermark bitmap is available, then one can use a VQ-like technique to forge a watermark into a new image. About the same time and independently, Coppersmith et al. proposed to use overlapping blocks to resist this attack. Although this method can make the attack inefficient, it does so with a significant loss of the localization property of the watermark. We extend in this paper the Wong schemes so that the resulting algorithms can resist the VQ attack and at the same time provide the same localization property in the watermark as the original schemes. The key idea is to insert a unique image-dependent block ID into the watermarking process so that the VQ attack will not have a rich enough 'codebook' to forge the watermark.© (2000) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
TL;DR: Active reset as mentioned in this paper uses bandlimiting and capacitive feedback to reduce reset noise in standard active pixel sensor (APS) and shows that reset noise can be reduced to less than kT/18C using active reset.
Abstract: Pixel reset noise sets the fundamental detection limit on photodiode based CMOS image sensors. Reset noise in standard active pixel sensor (APS) is well understood and is of order kT/C. In this paper we present a new technique for resetting photodiodes, called active reset, which reduces reset noise without adding lag. Active reset can be applied to standard APS. Active reset uses bandlimiting and capacitive feedback to reduce reset noise. This paper discusses the operation of an active reset pixel, and presents an analysis of lag and noise. Measured results from a 6 transistor per pixel 0.35 micrometers CMOS implementation are presented. Measured results show that reset noise can be reduced to less than kT/18C using active reset. We find that theory simulation and measured results all match closely.
TL;DR: New and improved attacks on the authentication scheme previously proposed by Yeung and Mintzer are described and it is shown how the scheme is still vulnerable, even if the binary logo is not known but the attacker has access to multiple images that have been watermarked with the same secret key and contain the same logo.
Abstract: In this paper, we describe new and improved attacks on the authentication scheme previously proposed by Yeung and Mintzer. Previous attacks assumed that the binary watermark logo inserted in an image for the purposes of authentication was known. Here we remove that assumption and show how the scheme is still vulnerable, even if the binary logo is not known but the attacker has access to multiple images that have been watermarked with the same secret key and contain the same (but unknown) logo. We present two attacks. The first attack infers the secret watermark insertion function and the binary logo, given multiple images authenticated with the same key and containing the same logo. We show that a very good approximation to the logo and watermark insertion function can be constructed using as few as two images. With color images, one needs many more images, nevertheless the attack is still feasible. The second attack we present, which we call the 'collage-attack' is a variation of the Holliman-Memon counterfeiting attack. The proposed variation does not require knowledge of the watermark logo and produces counterfeits of superior quality by means of a suitable dithering process that we develop.© (2000) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
TL;DR: In this article, a comparative analysis of the fundamental performance limits of quantization index modulation (QIM), distortion-compensated QIM, and other watermarking methods is presented.
Abstract: Quantization index modulation (QIM) methods, a class of digital watermarking and information embedding methods, achieve very efficient trade-offs among the amount of embedded information (rate), the amount of embedding-induced distortion to the host signal, and the robustness to intentional and unintentional attacks. For example, we show that against independent additive Gaussian attacks, which are good models for at least some types of uniformed and unintentional attacks, QIM methods exist that achieve the best possible rate-distortion-robustness trade-offs (i.e., capacity) asymptotically at high rates and achieve performance within a few dB of capacity at all finite rates. Furthermore, low- complexity realizations of QIM methods, such as so-called dither modulation, have also been shown to achieve favorable rate-distortion-robustness trade-offs. We further develop preprocessing and postprocessing techniques that enable QIM to fully achieve capacity, not only against Gaussian attacks but also against other types of attacks as well. One practical postprocessing technique we develop we refer to as distortion compensation. Distortion compensation has the property that when suitably optimized it is sufficient for use in conjunction with QIM to achieve capacity against Gaussian attacks and against square-error distortion-constrained attacks. More generally, we present the results of a comparative information theoretic analysis of the fundamental performance limits of QIM, distortion-compensated QIM, and other watermarking methods and demonstrate practically achievable gains with experimental results.© (2000) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
TL;DR: The experimental result shows that the proposed genetic algorithm based watermark optimization technique can effectively improve the quality of the watermarked image and the robustness of the embedded watermark against various attacks.
Abstract: In this paper, a genetic algorithm (GA) based watermark optimization technique for digital image watermarking is proposed. In our approach, watermark embedding positions are simulated by chromosomes, and several GA optimization operators such as reproduction, crossover, and mutation are used. The experimental result shows that the proposed approach can effectively improve the quality of the watermarked image and the robustness of the embedded watermark against various attacks. By analyzing the distribution of embedding positions, we found that watermark embedding positions are highly correlated to the energy distribution of block-DCT coefficients.
TL;DR: This paper describes methodological and technological possibilities as well as measurement technology applications for fast optical 3D shape measurements using micromirror-based high-velocity stripe projection in order to shoot and evaluate compete 3D surface profiles within only a few milliseconds.
Abstract: The fast, contact-free and highly precise shape measurement of technical objects is of key importance in the scientific- technological area as well as the area of practical measurement technology. The application areas of contact- free surface measurement extend across widely different areas, e.g., the automation of production processes, the measurement and inspection of components in microsystem technology or the fast 3D in-vivo measurement of human skin surfaces in cosmetics and medical technology. This paper describes methodological and technological possibilities as well as measurement technology applications for fast optical 3D shape measurements using micromirror-based high-velocity stripe projection. Depending on the available projector and camera facilities, it will be possible to shoot and evaluate compete 3D surface profiles within only a few milliseconds.
TL;DR: An analysis of the basic approaches to flat panel autostereoscopic 3D display is presented, and a near field diffraction model is used to analyze the detailed illumination structure of the output and can be used to assess viewing freedom and cross talk considerations.
Abstract: An analysis of the basic approaches to flat panel autostereoscopic 3D display is presented, together with a discussion of the application of LCDs in this field. We show that of particular importance in the design of parallax barrier type displays is the diffractive performance of the barriers. A near field diffraction model is used to analyze the detailed illumination structure of the output and can be used to assess viewing freedom and cross talk considerations. A comparison between front and rear parallax barrier displays is given, and compared with experimental result. Recent progress in the design of low cost flat panel 3D displays including a novel viewer position indicator and 2D/3D reconfigurable systems using novel patterned retarder elements are described. We describe the performance and manufacturing considerations for these elements.
TL;DR: A digital audio watermarking scheme of low complexity is proposed in this research as an effective way to deter users from misusing or illegally distributing audio data.
Abstract: Digital audio watermarking embeds inaudible information into digital audio data for the purposes of copyright protection, ownership verification, covert communication, and/or auxiliary data carrying. In this paper, we first describe the desirable characteristics of digital audio watermarks. Previous work on audio watermarking, which has primarily focused on the inaudibility of the embedded watermark and its robustness against attacks such as compression and noise, is then reviewed. In this research, special attention is paid to the synchronization attack caused by casual audio editing or malicious random cropping, which is a low-cost yet effective attack to watermarking algorithms developed before. A digital audio watermarking scheme of low complexity is proposed in this research as an effective way to deter users from misusing or illegally distributing audio data. The proposed scheme is based on audio content analysis using the wavelet filterbank while the watermark is embedded in the Fourier transform domain. A blind watermark detection technique is developed to identify the embedded watermark under various types of attacks.© (2000) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
TL;DR: Multiple views are useful for scientific exploration tasks of relating, coupling and to aid the 'drilling down' of information, and to provide alter-native viewpoints by expressing different user-interpretations of the same information.
Abstract: Visualization is about discovery and understanding; the user wishes to gain a correct insight into the underlying information, to explore and analyze how different parts are related. Thus, presentation, exploration and explanation tools are used with manipulation and investigative techniques to display, discover and gain a 'correct dissemination' of the information. Moreover, by displaying the information simultaneously in multiple ways the user is aided in their investigation. Such multiform techniques may be generated through various algorithms; we organize these methods according to how they apply to the individual stages of the dataflow paradigm. These multiforms may be displayed in separate windows. Multiple views are useful (1) to overcome misinterpretations and provide additional insight, (2) for scientific exploration tasks of relating, coupling and to aid the 'drilling down' of information, and (3) to provide alter-native viewpoints by expressing different user-interpretations of the same information. Finally, to use multiple views effectively they should be, among other things, easily created, automatically coupled to other views and dynamically manipulated.
TL;DR: In this article, the scaling factor of a previously scaled watermarked image and the angle by which the image has been rotated are estimated using the Edges Standard Deviation Ratio (ESDR) and the Average Edges Angles Difference (AEAD).
Abstract: In this paper we report a novel method to estimate the scaling factor of a previously scaled watermarked image and the angle by which the image has been rotated. Scaling and rotation performed on a watermarked image, as part of the attacks the image may undergo, can very easily confuse the decoder unless it rescales and/or rotates the image back to its original size/orientation, i.e., recover the lost synchronism. To be able do so, the decoder needs to know by how much the image has been scaled and rotated, i.e., needs to know both the scaling factor and the rotation angle. In our approach, we compute the Edges Standard Deviation Ratio (ESDR) which gives us an accurate estimate for the scaling factor. The rotation angle is approximated by the Average Edges Angles Difference (AEAD). Both ESDR an AEAD are computed from wavelet maxima locations which have been estimated form the non orthogonal dyadic wavelet transform. The proposed scheme does not require the original image provided that a proper normalization has been attained. Our method has proved its robustness to wide rotation and scale ranges.
TL;DR: The result of an extensive usability experiment show how visualization may lead to either increased or decreased cognitive load in the NIST Information Retrieval Visualization Engine.
Abstract: We discuss the evolution of the NIST Information Retrieval Visualization Engine. This prototype employs modern interactive visualization techniques to provide easier access to a set of documents resulting from a query to a search engine. The motivation and evaluation of several design features, such as keywork to concept mapping, explicit clustering, the use of 3D vs. 2D, and the relationship of visualization to logical structure are described. In particular, the result of an extensive usability experiment show how visualization may lead to either increased or decreased cognitive load.
TL;DR: In this article, the authors present experimental results from a 640 X 512 CMOS image sensor fabricated using a 0.35(mu) 4-layer metal CMOs process that shows significant QE reduction of up to 50% for off-axis relative to on-axis pixels.
Abstract: CMOS image sensor designers take advantage of technology scaling either by reducing pixel size or by adding more transistors to the pixel. In both cases, the distance from the chip surface to the photodiode increases relative to the photodiode planar dimensions. As a result, light must ravel through an increasingly deeper and narrower `tunnel' before it reaches the photodiode. This is especially problematic for light incident at oblique angles; the narrow tunnel walls cast a shadow on the photodiode, which in turn severely reduces its effective QE. We refer to this phenomenon as pixel vignetting. The paper presents experimental results from a 640 X 512 CMOS image sensor fabricated using a 0.35(mu) 4-layer metal CMOs process that shows significant QE reduction of up to 50% for off-axis relative to on-axis pixels. Using simple geometric models of the sensor and the imaging optics, we compare the QE for on and off-axis pixels. We find that our analysis results support the hypothesis that the experimentally observed QE reduction is indeed due to pixel vignetting. We show that pixel vignetting becomes more severe as CMOS technology scales, even for a 2-layer metal APS pixel. Finally, we briefly discuss several potential solutions to the pixel vignetting problem.
TL;DR: Wang et al. as mentioned in this paper proposed Data Hiding Pair-Toggling (DHPT), which hides data by forced complementary toggling at pseudo-random locations within a halftone image.
Abstract: With the ease of distribution of digital images, there is a growing concern for copyright control and authentication. While there are many existing watermarking and data hiding methods for natural images, almost none can be applied to halftone images. In this paper, we proposed two novel data hiding methods for halftone images. The proposed Data Hiding Pair-Toggling (DHPT) hides data by forced complementary toggling at pseudo-random locations within a halftone image. It is found to be very effective for halftone images with relatively coarse textures. For halftone images with fine textures (such as error diffusion with Steinberg kernel), the proposed Data Hiding Error Diffusion (DHED) gives significantly better visual quality by integrating the data hiding into the error diffusion operation. Both DHPT and DHED are computationally very simple and yet effective in hiding a relatively large amount of data. Both algorithms yield halftone images with good visual quality.
TL;DR: The results show that the schemes are robust to Stirmark and other geometric transformations on different categories of images.
Abstract: Numerical information is volatile and watermarking is a solution to assist copyright protection. During the detection step, the synchronisation of the mark is a great problem. Geometric transformations can defeat the detector of the mark by desynchronising the mark. Our scheme is based on warping of pre-defined triangular patterns. The content of the image (feature points) is used to mark independently different regions. This allows the synchronisation of the mark for the detection step. Feature points mixed with a Delaunay tessellation permits to mark each triangle of the image. The detection is performed by warping triangle to a reference pattern and correlating with a reference triangle. Different algorithms have been developed in the spatial domain and in the frequential (DCT) domain. Our results show that our schemes are robust to Stirmark and other geometric transformations on different categories of images.
TL;DR: An illustrated case study of the construction of a high-fidelity virtual environment, intended to match a particular real-life crime scene as closely as possible, is presented.
Abstract: This paper describes research conducted in collaboration with Greater Manchester Police (UK), to evalute the utility of Virtual Environments for scene of crime analysis, forensic investigation, and law enforcement briefing and training. We present an illustrated case study of the construction of a high-fidelity virtual environment, intended to match a particular real-life crime scene as closely as possible. We describe and evaluate the combination of several approaches including: the use of the Manchester Scene Description Language for constructing complex geometrical models; the application of a radiosity rendering algorithm with several novel features based on human perceptual consideration; texture extraction from forensic photography; and experiments with interactive walkthroughs and large-screen stereoscopic display of the virtual environment implemented using the MAVERIK system. We also discuss the potential applications of Virtual Environment techniques in the Law Enforcement and Forensic communities.
TL;DR: The development and construction of a large screen version of the Cambridge time-multiplexed autostereo display, using a 50 inch diagonal spherical mirror in place of the 10 inch Fresnel lens of the original Cambridge color display is described.
Abstract: We describe the development and construction of a large screen version of the Cambridge time-multiplexed autostereo display. The new device uses a 50 inch diagonal spherical mirror in place of the 10 inch Fresnel lens of the original Cambridge colour display. A fivefold increase in image luminance has been achieved by the replacement of sequential colour on a single CRT with separate red, green, and blue CRTs. Fifteen views are displayed at 640 〈480 (VGA) resolution with about 250 cd/m 2 luminance and 30 Hz (TV) interlaced refresh rate. A 22 mm inter-view separation provides three views between a typical viewer’s eyes, giving a smooth stereoscopic effect over a 330 mm wide eye box. Two identical optical systems have been built, sharing the single large spherical mirror, allowing simultaneous use of the device by two viewers. The two systems are off-axis with respect to the main mirror, requiring geometric compensation on the CRTs in addition to the normal colour convergence. The prototype produces two independent full colour, large, 3D images which can be viewed under normal lighting conditions.
TL;DR: This paper presents the problem of copyright protection and integrity checks for combined video and audio data with a combined robust and fragile watermarking approach and shows two solutions for the protection of audio and video data.
Abstract: Audio and video watermarking enable the copyright protection with owner or customer authentication and the detection of media manipulations. The available watermarking technology concentrates on single media like audio or video. But the typical multimedia stream consists of both video and audio data. Our goal is to provide a solution with robust and fragile aspects to guarantee authentication and integrity by using watermarks in combination with content information. We show two solutions for the protection of audio and video data with a combined robust and fragile watermarking approach. The first solution is to insert a time code into the data: We embed a signal as a watermark to detect gaps or changes in the flow of time. The basic idea uses numbers increasing by one. If in the verification process the next number is smaller than the last one or the step is greater than one, the time flow has been changed. This is realized without the combination of video and audio data. But we can synchronize the two data streams. A time signal is only valid if the combination of audio and video signals satisfy a certain attribute. To keep the basic example: if we embed an increasing a number in the audio and a decreasing number in the video, we could test if the combination of both always equals zero. The second solution is more complex: We use watermarks to embed information in each media about the content of the other media. With the help of speech recognition technology it is possible to embed the spoken text, the content, of an audio file in the video. With an algorithm previously developed in [1] we extract video content representation which is embedded in the audio stream. In our paper we present the problem of copyright protection and integrity checks for combined video and audio data. We show our two solutions and discuss our results.
TL;DR: A fragile technique that can detect the most minor changes in a marked image using a DCT-based data hiding method to embed a tamper-detection mark and a semi-fragile technique that detects the locations of significant manipulations while disregarding the less important effects of image compression and additive channel noise.
Abstract: In this paper, we present two tamper-detection techniques. The first is a fragile technique that can detect the most minor changes in a marked image using a DCT-based data hiding method to embed a tamper-detection mark. The second is a semi-fragile technique that detects the locations of significant manipulations while disregarding the less important effects of image compression and additive channel noise. Both techniques are fully described and the performance of each algorithms demonstrated by manipulation of the marked images.
TL;DR: Invisible watermark images can be incorporated in printed halftone images using specially designed Halftone screens usingpecially designed halFTone screens to detect the embedded spatial correlation information in the watermarked image.
Abstract: Invisible watermark images can be incorporated in printed halftone images using specially designed halftone screens. The watermark information is embedded into the image by varying the spatial correlation of the halftone texture. The halftone screen with embedded watermarks can be used exactly as a normal halftone screen, so there is no additional image processing required for processing individual images to embed watermarks. Once the binary output image is printed on the paper, the correlation of the binary image is converted into physical spatial correlation between neighboring areas of the printed image. This correlation relation is not visible to the eye but it can be detected by scanning the printed image on a desktop scanner and processing the scanned image. Printer and scanner distortions can interfere with the self-alignment of the scanned image, so localized adjustments are made to detect the embedded spatial correlation information in the watermarked image. The retrieval of this watermark is robust to copying and distortion and it can be detected in reproductions of the halftone image.