Showing papers by "Gaurav Sharma published in 2003"

Localized lossless authentication watermark (LAW)

Abstract: A novel framework is proposed for lossless authentication watermarking of images which allows authentication and recovery of original images without any distortions. This overcomes a significant limitation of traditional authentication watermarks that irreversibly alter image data in the process of watermarking and authenticate the watermarked image rather than the original. In particular, authenticity is verified before full reconstruction of the original image, whose integrity is inferred from the reversibility of the watermarking procedure. This reduces computational requirements in situations when either the verification step fails or the zero-distortion reconstruction is not required. A particular instantiation of the framework is implemented using a hierarchical authentication scheme and the lossless generalized-LSB data embedding mechanism. The resulting algorithm, called localized lossless authentication watermark (LAW), can localize tampered regions of the image; has a low embedding distortion, which can be removed entirely if necessary; and supports public/private key authentication and recovery options. The effectiveness of the framework and the instantiation is demonstrated through examples.

System and method for obtaining color consistency for a color print job across multiple output devices

Abstract: A method for maintaining color consistency in an environment of networked devices is disclosed. The method involves identifying a group of devices to which a job is intended to be rendered; obtaining color characteristics from devices in the identified group; modifying the job based on the obtained color characteristics; and rendering the job on one or more of the devices. Modifications are computed by a transform determined by using the color characteristics of the output devices along with the content of the job itself. The method further maps colors in the original job to the output devices' common gamut, i.e., intersection of the gamuts of the individual printers wherein the color gamut of each device is obtained from a device characterization profile either by retrieving the gamut tag or by derivation using the characterization data in the profile.

Collusion-resilient fingerprinting using random prewarping

Abstract: Fingerprinting of audio-visual content using digital watermarks is an effective means of determining the originators of unauthorized copies and fighting piracy in digital distribution networks. In particular, watermarks embedded within the content help trace the traitor responsible for the piracy. A group of users may, however, collude and collectively escape identification by creating an average of their individually watermarked copies that appears unwatermarked. We propose a novel collusion-resilience mechanism, wherein the host signal is warped randomly prior to watermarking. As each copy undergoes a distinctive warp, collusion through averaging either yields low-quality results or requires substantial computational resources to undo random warps. The proposed method is independent of the watermarking scheme used and does not impose any restrictions on the watermark signal that are required by some collusion resistant watermarking schemes. We demonstrate the effectiveness of this approach on digital images.

Systems and methods for associating color profiles with a scanned input image using spatial attributes

Abstract: Methods and systems used to associate color calibration profiles with scanned images based on identifying the marking process used for an image on a substrate using spatial characteristics and/or color of the image. Image types which are classified and identified include continuous tone images and halftone images. Among halftone images separately identified are inkjet images, xerographic images and lithographic images. Locally adaptive image threshold techniques may be used to determine the spatial characteristics of the image.

System and method for embedding information in digital signals

Abstract: A lossless, reversible data embedding technique uses a generalization of least-significant-bit modification. The portions of the signal that are susceptible to embedding distortion are compressed and sent as part of the embedded payload. A prediction-based conditional entropy coder uses unaltered portions of the host signal to improve lossless data capacity.

Gray-level-embedded lossless image compression

Abstract: A level-embedded lossless compression method for continuous-tone still images is presented. Level (bit-plane) scalability is achieved by separating the image into two layers before compression and excellent compression performance is obtained by exploiting both spatial and inter-level correlations. A comparison of the proposed scheme with a number of scalable and non-scalable lossless image compression algorithms is performed to benchmark its performance. The results indicate that the level-embedded compression incurs only a small penalty in compression efficiency over non-scalable lossless compression, while offering the significant benefit of level-scalability.

Two-dimensional calibration architectures for color devices

Abstract: A color output device is generally driven by at least three independent control signals for control of its response. A desired response in device independent color space is normally obtained by employing a cascade consisting of a characterization transform and calibration transform. The calibration transform transforms input control variables into output control variables that are directly used to drive the device. Input control variables can be transformed into intermediate control variables, which can be then mapped to output control variables utilizing a two-dimensional transformation. The two-dimensional calibration architecture provides improved control functionality and flexibility.

Method for standardizing input CMYK values for clustered printing environments

Abstract: The present invention implements a CMYK to CMYK pre-transform in front of at least one printer to be clustered where the transform is designed to ensure that the printers addressed through the pre-transform have substantially identical output color for substantially identical input CMYK values. As one form of implementation a method is disclosed to build CMY to CMY 3D-LUTs and 1D-LUT for K using sensors in the field. Making use of a system LUT—CMY to CMY 3D-LUT and a K to K 1D-LUT—improves consistency and provides a coherent control strategy and a means to provide standardized input CMY and K values in a clustered environment so that single or multiple vendor DFEs see substantially identical CMYK values.

Charge transfer and photogeneration process in device consisting of safranine O dye and TiO2 nano-particles

Abstract: We have studied the effect of titanium dioxide (TiO 2 ) nano-particles on charge transfer processes in safranine O (SAF) dye photovoltaic device. The photoconductivity is increased by two orders and a sharp saturation is also observed. The device shows a sharp saturation in photocurrent in forward bias which indicates that exciton diffusion and dissociation at the TiO 2 interface, due the existence of internal electric field is dominant process for the collection of charge. The value of diode quality factor has been calculated also by fitting the experimental results with modified Shockley equation. The internal electric field is mainly due to the asymmetry between the work functions of the materials. Electron injection from the excited state of dye on illumination, into the conduction band of TiO 2 is followed by subsequent hole transfer from the photooxidized dye to the collecting Al electrode, regenerating the dye's original ground state. The charge transfer and photogeneration process in device have been discussed on the basis of current–voltage characteristics and photoaction action spectra of the device.

Color Printer Characterization Adjustment for Different Substrates

Abstract: The use of multiple substrates in color printers requires color characterization for each of the individual substrates. A full re-characterization for each substrate is measurement and labor intensive. In this article, a variety of methods are proposed and evaluated for determining the color characterization for a new substrate based on a complete characterization on a reference substrate and a small number of additional measurements for the new substrate. This saves significant time and effort in comparison to the traditional method of repeating the color characterization for each new substrate. The methods developed and tested include model-based approaches based on Beer's law, Kubelka-Munk theory, and Neugebauer equations; and an empirical technique based on principal component analysis. Results indicate that the model based techniques offer only a small improvement over direct use of the reference characterization, whereas, the empirical technique offers a more significant improvement with as few as 26 measurements on the new substrate. © 2003 Wiley Periodicals, Inc. Col Res Appl, 28, 454–467, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.10198

Systems for spectral multiplexing of source images to provide a composite image, for rendering the composite image, and for spectral demultiplexing the composite image to obtain a normalized color image

Abstract: Methods and apparatus for spectrally-encoding plural source images and for providing the spectrally-encoded plural source images in a composite image, for rendering the composite image in a physical form, or for recovering a normalized version of an encoded source image from the rendered composite image such that the recovered source image is made distinguishable as a normalized color image.

Illuminant-neutral gray component replacement in systems for spectral multiplexing of source images to provide a composite image, for rendering the composite image, and for spectral demultiplexing of the composite image

Abstract: Methods and apparatus for spectrally-encoding plural source images and for providing the spectrally-encoded plural source images in a composite image, for rendering the composite image in a physical form, or for recovering at least one of the encoded source images from the rendered composite image such that the recovered source image is made distinguishable. Source image confusion in a rendered composite image is controlled by application of a illuminant-neutral gray component replacement (GCR) technique to the darkness common to the different colorants under the multiple illuminants.

Illuminant Multiplexed Imaging: Special Effects Using GCR.

Abstract: A novel spectral imaging technique is presented that allows multiple grayscale images to be combined in a single hardcopy print. The images are individually revealed when the print is illuminated by suitably chosen illuminants. In its basic form, the technique utilizes the complementary relation between cyan, magenta, and yellow colorants and narrow-band red, green, and blue illumination to combine and extract images. Colorant interactions are compensated through a simple calibration process. In addition, we present techniques demonstrating how gray component replacement (GCR) may be defined for illuminant multiplexed imaging and how it may be successfully exploited to allow embedding of additional patterns in the print that are revealed under uncontrolled illumination. The paper is accompanied by a light-booth based demonstration of illuminant multiplexed imaging and the effects described herein.

System and method for selecting the best set of devices for rendering color documents

Abstract: The system for selecting a best device for rendering a color document involves first determining the types of color data included in the color document to be printed. Once the type of color data has been determined, the color characteristics are matched against the strengths of the available output devices to obtain a list of devices best suited for this particular color print job. At least one device from the list of best devices is selected and the color document is rendered onto the selected device. Preferably, the types of color data involved are determined by the mix of defined colorimetry and undefined colorimetry in the color document. Alternatively, the types of color data are determined by analyzing the colorspaces in the document (i.e., RGB, CMYK, LAB, XYZ, etc.), and the embedded profiles, if any, in the document (e.g., sRGB, SWOPCMYK, Euroscale). In the instance wherein a number of devices match the criteria for selection, only those devices which honor embedded color profiles are selected for documents containing embedded profiles. Alternatively, only those devices are selected that produce a consistent rendering across multiple color spaces and profiles for documents with a mix of color spaces and profiles. Selecting the best device may also depend on whether the type of print job is considered to be Job-Balancing or Job-Splitting. With Job-Balancing, at least one of the metrics is used: (i) Intersection Gamut Volume, (ii) Gamut Similarity, or (iii) Mismatch Between Document Colors and Intersection Gamut for device selection. With Job-Splitting, at least one of these metrics are used: (i) Individual Gamut Volume, or (ii) Mismatch Between Document Colors and Device Gamut. Colorimetric definition of the selected colors can be retrieved from either an embedded source profile or by default and mapping the colors to the output gamut.

Systems for spectral multiplexing of source images to provide a composite image, for rendering the composite image, and for spectral demultiplexing of the composite image

Abstract: Methods and systems for spectrally-encoding plural source images and for providing the spectrally-encoded plural source images in a composite image, for rendering the composite image on a substrate, and for recovering at least one of the encoded source images from the rendered composite image. A desired source image is recovered when the rendered composite image is subjected to illumination by one or more illuminants and the desired source image is detected by one or more sensors in an image capture device. The spectral characteristics of the colorants, illuminants, and sensors are employed to spectrally encode the source image in the composite image.

Systems and methods for estimating an image marking process using event mapping of scanned image attributes

Abstract: Methods and systems used to automatically identify the marking process used for an image on a substrate based on spatial characteristics and/or color of the image. Image types which are classified and identified include continuous tone images and halftone images. Among halftone images separately identified are inkjet images, xerographic images and lithographic images. Locally adaptive image threshold techniques may be used to determine the spatial characteristics of the image.

Intermetallic growth between lead-free solders and palladium

Abstract: Intermetallic growth between Pd and the lead-free solders Sn-Ag and Sn-Ag-Cu has been studied. Diffusion couples were prepared by reflowing the solders on Pd and then aging the couples at 156°C, 175°C, 195°C, and 210°C. At the higher temperatures of 175°C, 195°C, and 210°C, PdSn4 made up most of the layer that grew between the solders and the Pd, although small regions of second phases were always found in the PdSn4 matrix, and it was sometimes possible to identify discontinuous regions of PdSn3 next to the Pd. The thickness of the intermetallic layer increased with the square root of time, consistent with diffusion-controlled growth. In couples annealed at 156°C, the morphology of the PdSn3 phase and growth kinetics differed depending on the composition of the solder.

Illuminant Multiplexed Imaging: Basics and Demonstration

Abstract: We present a novel spectral imaging technique that allows multiple gray-scale images to be combined in a single hardcopy print. The images are individually revealed when the print is illuminated by suitably chosen light sources. In its basic form, the technique utilizes the complementary relation between cyan, magenta, and yellow colorants and narrow band red, green, and blue illuminants to combine and extract the images. Instead of the conventional color imaging scenario, where three-dimensional color attributes of a print are controlled under a wide-band illuminant using a set of colorants, in illuminant multiplexed imaging, one dimensional luminance attributes under two or more narrow-band illuminants are simultaneously controlled using the same colorants. We present a brief mathematical framework for illuminant multiplexed imaging and describe useful approximations that significantly simplify implementation. Several applications of the technology are presented.

Two-dimensional transforms for device color calibration

Abstract: Color device calibration is traditionally performed using one-dimensional per-channel tone-response corrections (TRCs). While one-dimensional TRCs are attractive in view of their low implementation complexity and efficient real-time processing of color images, their use severely restricts the degree of control that can be exercised along various device axes. A typical example is that 1-D TRCs in a printer can be used to either ensure gray balance along the C = M = Y axis or to provide a linear response in ΔE units along each of the individual (C, M and Y) axis but not both. This paper proposes a novel two-dimensional calibration architecture for color device calibration that enables significantly more control over the device color gamut with a modest increase in implementation cost. Results show significant improvement in calibration accuracy and stability when compared to traditional 1-D calibration.

Level-embedded lossless image compression

Abstract: A level-embedded lossless compression method for continuous-tone still images is presented. Level (bit-plane) scalability is achieved by separating the image into two layers before compression and excellent compression performance is obtained by exploiting both spatial and inter-level correlations. A comparison of the proposed scheme with a number of scalable and non-scalable lossless image compression algorithms is performed to benchmark its performance. The results indicate that the level-embedded compression incurs only a small penalty in compression efficiency.

Error-Diffusion Robust to Mis-Registration in Multi-Pass Printing.

Abstract: Error-diffusion and its variants are commonly used halftoning techniques that produce dispersed dot (FM) halftones, which are often preferred because they are free from low-frequency structure. Since the isolated dots resulting from error diffusion are reproduced well on inkjet printers, error diffusion is commonly employed in these devices. Inkjet printers often print a page in two passes in order to allow for better drying of inks and to minimize appearance of a head signature. Any potential misregistration between the passes is typically not comprehended in the error-diffusion halftoning process. The mis-registration between the passes can therefore cause significantly increased graininess (low-frequency structure) in printed error diffusion images even though the electronic bitmaps generated by error diffusion are free from low-frequency structure. In this paper, we propose modifications to the error-diffusion halftoning process that take the two pass printing into account and produce halftones that are robust to inter-pass mis-registration errors. This allows reduced tolerances and alignment requirements in manufacturing that translate to lower cost. The proposed technique works by suitably biasing the error diffusion process to ensure that a majority of the minority pixels are concentrated in a single pass, which provides improved robustness to mis-registration between the passes. Experimental results demonstrate that the modified error-diffusion technique performs significantly better than regular error diffusion in the presence of mis-registration errors.

Determination of age from teeth using index value of attrition

Abstract: Study was conducted in LHMC & Associated Smt Sucheta Kriplani Hospital New Delhi to estimate age from central maxillary incisor by calculating the index value of attrition. Total number of cases studied was one hundred and fifty. The objectives of the study were to evaluate the degree of attrition as objectively as possible, neutralizing the role of oral pathology and its correlation with age.

System and method for making separated multi-color layer halftone by diffusing interlayer errors

Abstract: PROBLEM TO BE SOLVED: To diffuse errors between color separated layers made halftone SOLUTION: A method for generating a halftone image from a continuous tone image, having a plurality of color separation layers includes steps of making a first layer halftone for the plurality of color separation layers, generating a first color halftone separation layer, generating a first color error separation layer, on the basis of the first color separation layer and the first color halftone separation layer, modifying a second layer of the plurality of color separation layers to form a modified second color separation layer on the basis of at least the first color error separation layer, and making the modified second color separation layer to form a second color halftone separation layer COPYRIGHT: (C)2003,JPO

Systems for spectral multiplexing, rendering, and demultiplexing of source images

Abstract: Methods and apparatus for spectrally-encoding plural source images and for providing the spectrally-encoded plural source images in a composite image, for rendering the composite image in a physical form, or for recovering at least one of the encoded source images from the rendered composite image such that the recovered source image is made distinguishable. Source image confusion in a rendered composite image is controlled.

Photosensitive imaging apparatus sensitive to orange light

Abstract: A photosensitive imaging device for recording images across the entire visible spectrum includes a set of photosensors which have a peak response around the orange part of the spectrum, about 600 nm. The peak response is obtained by combining responses of, in one case, photosensors associated with a filter which admits red or infrared wavelengths and longer and photosensors associated with a filter which admits orange wavelengths and longer. In another case, the photosensor is structured to attenuate longer wavelengths, which, in combination with a filter which admits orange and longer wavelengths, can simulate a peak behavior around the orange part of the spectrum.

Level-Successive Encoding for Digital Photography.

Abstract: We propose a level-successive encoding scheme for the compression of continuous tone images. The compressed bit stream is partitioned into individual segments corresponding to successive bits and arranged in order of decreasing significance of the bits. Bit-plane scalability is achieved by recursively partitioning the image into an LSB bit-plane and remaining higher order bits and encoding the LSB bit-plane using the remaining bits as context. This allows the scheme to achieve excellent compression performance by exploiting both spatial and inter-level correlations. We compare the proposed scheme with a number of scalable and non-scalable lossless image compression algorithms to benchmark its performance. Results indicate that the level-embedded compression incurs only a small penalty in compression efficiency over conventional lossless schemes while offering the benefit of easy bit-plane scalability.

Stochastic screens robust to misregistration in multipass printing

Abstract: A new technique for design of stochastic screens is proposed that produces screens that are robust against mis-registration in multi-pass printing. Conventional stochastic screens are designed through an optimization process that minimizes low-frequency structure in halftone images under the assumption that the placement of pixels is accurate. In inkjet printing, however, a page is often printed in multiple passes to allow for better drying of inks and to minimize appearance of a head signature. Any potential mis-registration between the passes is typically not comprehended in the conventional stochastic screen design process. The mis-registration between the passes can therefore cause significantly increased graininess (low-frequency structure) in printed images produced with stochastic screens even though the corresponding electronic bitmaps are free from low-frequency structure. In this paper, we propose modifications to the stochastic screen design process that take the two pass printing into account and produce halftones that are robust to inter-pass mis-registration errors. This allows reduced tolerances and alignment requirements in manufacturing that translate to lower cost. The proposed technique works by modifying the screen design process to ensure that a majority of the minority pixels are concentrated in a single pass, which provides improved robustness to mis-registration between the passes. Experimental results demonstrate that the proposed design technique performs significantly better than conventional stochastic screens in the presence of mis-registration errors.

Robust Processing of Color Target Measurements for Device Characterization.

Abstract: Device characterization typically involves generating one or more targets each comprising a number of color patches and making colorimetric measurements of these patches. In order to derive the characterization function, one has to obtain the correspondence between the set of colorimetric measurements and a set of device signals. In the case of output device characterization, the device signals are the CMY(K) values used to create the target; for input device characterization the device signals are the captured RGB values. Establishing the correspondence requires knowledge of the spatial target layout, the order in which the measurement instrument measures the patches, and the order in which the input or output device captures or renders respectively the target patches. Since the measurement process requires human intervention, errors can conceivably be introduced at this step. A common example is misorientation of the target on the measurement stage. This results in an incorrect correspondence between device and colorimetric signals, thus producing an erroneous characterization. This paper presents some practical approaches to detect and correct for measurement errors due to misorientation. One approach reserves a number of patches in the target to encode the target layout and orientation. The measurements from this so-called “patch code” are then decoded to retrieve, and if necessary, correct the orientation. Another approach anticipates common misorientations of the target, and uses a pattern matching approach to select the correct orientation. This is done either automatically with a prior device characterization, or with visual validation by the user. Both techniques are successful in correcting for target misorientation with minimal burden to the user.