Showing papers on "Channel (digital image) published in 2002"

Color texture moments for content-based image retrieval

Abstract: We adopt a local Fourier transform as a texture representation scheme and derive eight characteristic maps for describing different aspects of cooccurrence relations of image pixels in each channel of the (SVcosH, SVsinH, V) color space. Then we calculate the first and second moments of these maps as a representation of the natural color image pixel distribution, resulting in a 48-dimensional feature vector. The novel low-level feature is named color texture moments (CTM), which can also be regarded as a certain extension to color moments in eight aspects through eight orthogonal templates. Experiments show that this new feature can achieve good retrieval performance for CBIR.

A vision-based masking model for spread-spectrum image watermarking

Abstract: We present a perceptual model for hiding a spread-spectrum watermark of variable amplitude and density in an image. The model takes into account the sensitivity and masking behavior of the human visual system by means of a local isotropic contrast measure and a masking model. We compare the insertion of this watermark in luminance images and in the blue channel of color images. We also evaluate the robustness of such a watermark with respect to its embedding density. Our results show that this approach facilitates the insertion of a more robust watermark while preserving the visual quality of the original. Furthermore, we demonstrate that the maximum watermark density generally does not provide the best detection performance.

Spatio-temporal channel for images

Abstract: A channel is inserted into a sequence of image frames by varying one or more display characteristics of the image across a display (118) in accordance with a spatio-temporal pattern applied to successive lines of each modified frame to watermark the image. B-frames are preferably modified if the image is MPEG encoded (108). The blue color component of the video signal may be modified with watermark information (106) and its complement in counter-phase rotations of successive lines in pairs of frames. Modification occurs in relatively still regions of the image having a sufficient level of blue-lightness. A watermark detector (116) has a priori information about the watermark, and examines specific (still) regions of the image over time that may contain the watermark. For detection, the difference in pixel values is calculated in still regions between the received test frame and either a) the non-modified image frame or b) the successive frame of a pair.

Geometry and Color in Natural Images

Abstract: Most image analysis algorithms are defined for the grey level channel, particularly when geometric information is looked for in the digital image. We propose an experimental procedure in order to decide whether this attitude is sound or not. We test the hypothesis that the essential geometric contents of an image is contained in its level lines. The set of all level lines, or topographic map, is a complete contrast invariant image description: it yields a line structure by far more complete than any edge description, since we can fully reconstruct the image from it, up to a local contrast change. We then design an algorithm constraining the color channels of a given image to have the same geometry (i.e. the same level lines) as the grey level. If the assumption that the essential geometrical information is contained in the grey level is sound, then this algorithm should not alter the colors of the image or its visual aspect. We display several experiments confirming this hypothesis. Conversely, we also show the effect of imposing the color of an image to the topographic map of another one: it results, in a striking way, in the dominance of grey level and the fading of a color deprived of its geometry. We finally give a mathematical proof that the algorithmic procedure is intrinsic, i.e. does not depend asymptotically upon the quantization mesh used for the topographic map. We also prove its contrast invariance.

LAM: luminance attenuation map for photometric uniformity in projection based displays

Abstract: Large-area multi-projector displays show significant spatial variation in color, both within a single projector's field of view and across different projectors. Recent research in this area has shown that the color variation is primarily due to luminance variation. Luminance varies within a single projector's field of view, across different brands of projectors and with the variation in projector parameters. Luminance variation is also introduced by overlap between adjacent projectors. On the other hand, chrominance remains constant throughout a projector's field of view and varies little with the change in projector parameters, especially for projectors of the same brand. Hence, matching luminance response of all the pixels of a multi-projector display should help us to achieve photometric uniformity.In this paper, we present a method to do a per channel per pixel luminance matching. Our method consists of a one-time calibration procedure when a luminance attenuation map (LAM) is generated. This LAM is then used to correct any image to achieve photometric uniformity. In the one-time calibration step, we first use a camera to measure the per channel luminance response of a multi-projector display and find the pixel with the most "limited" luminance response. Then, for each projector, we generate a per channel LAM that assigns a weight to every pixel of the projector to scale the luminance response of that pixel to match with the most limited response. This LAM is then used to attenuate any image projected by the projector.This method can be extended to do the image correction in real time on traditional graphics pipeline by using alpha blending and color look-up-tables. To the best of our knowledge, this is the first effort to match luminance across all the pixels of a multi-projector display. Our results show that luminance matching can indeed achieve photometric uniformity.

Enhancing embedding of out-of-phase signals

Abstract: The present invention relates to steganographically hiding images and information. In a preferred embodiment, an image is hidden within a media signal. The media preferably includes a cyan (C) color plane, a magenta (M) color plane, a yellow (Y) color plane and a black (K) color plane. In an alternative embodiment, the media includes a spot color. The image is converted into a black color channel image and is then applied to the media's K channel. The black channel image is inverted and the inverted image is applied to the media's CMY (or spot) color planes. The C, M and/or Y channels can be investigated to determine whether the image's signal level should be modified. In a related embodiment, the media signal is segmented into a plurality of blocks and the detection level of a first embedded block is determined to be sufficient before the embedding continues to a second block. In still another embodiment, visible spectrum detection of our out-of-phase digital watermark provides a clue as to whether a printing process needs calibration or is misaligned.

Perceptual Evaluation of Tone Mapping Operators with Regard to Similarity and Preference

Abstract: For years, 24-bit images effectively using 256 values for each color channel wereconsidered accurate enough to be used in the creation and display of photorealisticimagery. On the other end, photographers knowing the limitation of cameras andfilms would never attempt to photograph a scene including a light source placed inthe camera’s field of vision. However, as a result of global illumination renderingand high dynamic range (HDR) imaging [DM97], it is now common to generateimages spanning a huge range of luminance. Dealing with such images in elec-tronic form requires extending file formats that are restricted to too few luminancevalues and colors. An even more serious issue is effective displaying/printing ofthose images using media with limited dynamic range (both in reproducible lumi-nance values and color gamut).The first limitation was successfully addressed in different pixel encoding for-mats. A simple approach relies on using three floating point numbers for eachpixel RGB values, however, this leads to excessive file sizes. The HDR imagesize can be reduced to four bytes for each pixel using the RGBE format [War91],in which a common exponent and a mantissa are assumed for each channel thusallowing a wide dynamic range with little storage overhead. Another format, thelogLuv encoding for tiff images [Lar98] separates a logarithmic representation ofluminance and aCIE

Designing effective transfer functions for volume rendering from photographic volumes

Abstract: Photographic volumes present a unique, interesting challenge for volume rendering. In photographic volumes, the voxel color is pre-determined, making color selection through transfer functions unnecessary. However, photographic data does not contain a clear mapping from the multi-valued color values to a scalar density or opacity, making projection and compositing much more difficult than with traditional volumes. Moreover, because of the nonlinear nature of color spaces, there is no meaningful norm for the multi-valued voxels. Thus, the individual color channels of photographic data must be treated as incomparable data tuples rather than as vector values. Traditional differential geometric tools, such as intensity gradients, density and Laplacians, are distorted by the nonlinear non-orthonormal color spaces that are the domain of the voxel values. We have developed different techniques for managing these issues while directly rendering volumes from photographic data. We present and justify the normalization of color values by mapping RGB values to the CIE L*u*v* color space. We explore and compare different opacity transfer functions that map three-channel color values to opacity. We apply these many-to-one mappings to the original RGB values as well as to the voxels after conversion to L*u*v* space. Direct rendering using transfer functions allows us to explore photographic volumes without having to commit to an a-priori segmentation that might mask fine variations of interest. We empirically compare the combined effects of each of the two color spaces with our opacity transfer functions using source data from the Visible Human project.

Masking Model for Accurate Colorimetric Characterization of LCD.

Abstract: Acolor management system (CMS) such as ICC profile or sRGB space have been proposed for color transformation and reproduction of cross media. In such a CMS, accurate colorimetric characterization of a display device plays a critical role in achieving device-independent color reproduction. In the case of a CRT, colorimetric characterization based on a GOG model is accurate enough for this purpose. However, there is no effective counterpart in liquid-crystal displays (LCDs) since the characterization of an LCD has many difficulties, such as channel interaction and non-constancy of channel chromaticity. In this paper, a new method of display characterization is proposed which is applicable to the assessment of color reproduction of LCDs. The proposed method characterizes an electro-optical transfer function considering both channel interaction and non-constancy of channel chromaticity. Experimental results show that the proposed method is very effective in the colorimetry of LCDs.

Evaluation and optimal design of spectral sensitivities for digital color imaging

Abstract: The quality of an image captured by color imaging system primarily depends on three factors: sensor spectral sensitivity, illumination and scene. While illumination is very important to be known, the sensitivity characteristics is critical to the success of imaging applications, and is necessary to be optimally designed under practical constraints. The ultimate image quality is judged subjectively by human visual system. This dissertation addresses the evaluation and optimal design of spectral sensitivity functions for digital color imaging devices. Color imaging fundamentals and device characterization are discussed in the first place. For the evaluation of spectral sensitivity functions, this dissertation concentrates on the consideration of imaging noise characteristics. Both signal-independent and signal-dependent noises form an imaging noise model and noises will be propagated while signal is processed. A new colorimetric quality metric, unified measure of goodness (UMG), which addresses color accuracy and noise performance simultaneously, is introduced and compared with other available quality metrics. Through comparison, UMG is designated as a primary evaluation metric. On the optimal design of spectral sensitivity functions, three generic approaches, optimization through enumeration evaluation, optimization of parameterized functions, and optimization of additional channel, are analyzed in the case of the filter fabrication process is unknown. Otherwise a hierarchical design approach is introduced, which emphasizes the use of the primary metric but the initial optimization results are refined through the application of multiple secondary metrics. Finally the validity of UMG as a primary metric and the hierarchical approach are experimentally tested and verified.

Color separation method and printed product of the method

Abstract: A method is described for overcoming the adverse visual effect of misregistered ink planes in multiple ink color prints. Color separations are initially made in a normal fashion. The separation carrying the greatest object detail is then chosen as a luminance or achromatic channel. This may be used as is or preferably it is sharpened using a high pass filter. Normally this separation will be black. However, it may be a surrogate color for black, particularly if only two or three separations are made. Object detail in all other separations (chrominance separations) is degraded, usually by a low pass filter such as a Gaussian blur. The printed image formed when the separations are recombined in a conventional manner is remarkably visually tolerant of misregistration of the various ink planes in the image.

Color transformation for processing digital images

Abstract: A method of transforming the color appearance of a plurality of digital images includes receiving a plurality of digital images from a capture medium wherein each digital image includes a plurality of pixel values relating to at least three basic colors; calculating a color correction transform by using a non-linear adjustment that is independent of the digital images and which corrects an under-exposure condition as a function of the capture medium; and a linear functional relationship dependent upon the pixels of the basic colors, the linear functional relationship defining an exposure-level-dependent estimate of gray corresponding to the photographic response of the capture medium; and using the color correction transform to modify the pixels of the plurality of digital images wherein the pixels within a digital image are transformed with varying degrees of color modification as a function of exposure

Arrangement and method for spatial visualization

Abstract: An apparatus for image data computation and for synchronous data output. An arrangement for producing and reproducing two partial light images which together can be perceived as a light image having a three-dimensional effect. A method of synchronous reproduction of time image sequences by at least two image reproduction devices. The apparatus according to an embodiment of the present invention has a master-client structure. A graphics master unit and at least two graphics clients are connected together by way of a first message channel and by way thereof exchange first messages, such that computation and projection of the partial images is synchronized.

Prediction-based image restoration using a multiple window configuration

Abstract: We present a prediction-based multiple-window approach to image restoration based on new hypotheses. The filter is an order statistics filter that incorporates the new hypotheses via the generation of a reference image to predict the original uncorrupted image. In addition, adaptive parameter selection based on the local signal content is employed, as well as off-line parameter optimization and training using a maximum-likelihood estimation algorithm. The experimental results are all carried out using 24-bit RGB images with each channel being processed individually. The new technique demonstrates a marked performance gain over existing state-of-the-art methods.

Recognition of two-phase flow patterns with the use of dynamic image analysis

Abstract: This research work aimed at developing techniques for the recognition of two-phase flow patterns using image analysis. Flow was realized in a flat rectangular channel. Information recorded with a CCD camera, was analysed using the authors' own software. The change in the grey level value from the recorded flow realizations was investigated. The results of this analysis allowed identification of the two-phase flow structures obtained. Stochastic analysis of the fluidization process was also carried out.

Method of color interpolation in a single sensor color camera using green channel separation

Abstract: This paper presents a color interpolation algorithm for a single sensor color camera The proposed algorithm is especially designed to solve the problem of pixel crosstalk among the pixels of different color channels Interchannel cross-talk gives rise to blocking effects on the interpolated green plane, and also spreading of false colors into detailed structures The proposed algorithm separates the green channel into two planes, one highly correlated with the red channel and the other with the blue channel These separate planes are used for red and blue channel interpolation Experiments conducted on McBeth color chart and natural images have shown that the proposed algorithm can eliminate or suppress blocking and color artifacts to produce better quality images

Sound image localizing signal processing apparatus and sound image localizing signal processing method

Abstract: PROBLEM TO BE SOLVED: To provide a sound image localizing signal processing apparatus and a sound image localizing signal processing method capable of localizing a sound image in a direction of a moving video image even in the case of moving and reproducing the video image with a changed angle for reproduction of an audio signal with respect to a free viewpoint video image. SOLUTION: The sound image localizing signal processing apparatus includes: a viewpoint selection section 5 for selecting viewpoint selection information of a user acting like angle information of a reproduced sound image of a video image on the basis of a video signal; a channel mapping section 6 for applying signal processing in real time for localizing the sound image to a channel of the audio signal corresponding to the viewpoint selection information of the user used for angle information of the selected reproduction sound image; a meta data section 9 for producing meta data to perform the signal processing; and an audio interleave section 11 for superimposing the audio signal and the meta data on the video signal to produce transmission information, and applies signal processing to the audio signal in real time so as to control the sound image localizing position corresponding to the video image on the basis of the video signal. COPYRIGHT: (C)2004,JPO

Channel Representation of Colour Images

Abstract: In this report we describe how an RGB component colour image may be expanded into a set of channel images, and how the original colour image may be reconstructed from these We also demonstrate the

Image processing method and system to increase perceived visual output quality in case of lack of image data

Abstract: A digital video processing system is disclosed in which processing modules use less data packets than in the regular situation in which there enough data is received. In case of a channel change, the digital video processing system can, during a time period in which there is a lack of data, produce more images than the prior art systems. These images have lower quality than the ones that result from regular processing, but a person will perceive the image quality to be higher than the one of the prior art.

Method and apparatus for computing thresholds for identification of waveform anomalies

Abstract: Apparatus in accordance with the subject invention maintains an exponentially decayed histogram of the counts of new pixels for each active channel, together with a running count of time and number of acquisitions. At regular intervals determined by a maximum time or by a minimum number of acquisitions it computes a new threshold for each active channel. This threshold will theoretically produce “N” nominally unusual waveforms per second where N is defined by a user “sensitivity” control. The raw histogram is smoothed to provide a stable “tail” of small probabilities. Once a threshold has been determined, subsequent waveforms with more than this number of new pixels are re-examined to determine the number of “really new” pixels. “Really new” pixels are defined as those that are not adjacent to pixels remaining from earlier acquisitions. Only those waveforms that have more “really new” pixels than a specified fraction of the basic threshold are reported as anomalies.

Digital red eye removal

Abstract: The current paper provides methods to correct the artifact known as red eye by means of digital color image processing. This artifact is typically formed in amateur photographs taken with a built-in camera flash. To correct red eye artifacts, an image mask is computed by calculating a colorimetric distance between a prototypical reference red eye color and each pixel of the image containing the red eye. Various image processing algorithms such as thresholding, blob analysis, and morphological filtering, are applied to the mask, in order to eliminate noise, reduce errors, and facilitate a more natural looking result. The mask serves to identify pixels in the color image needing correction, and further serves to identify the amount of correction needed. Pixels identified as having red eye artifacts are modified to a substantially monochrome color, while the bright specular reflection of the eye is preserved.

Color image watermarking using channel-state knowledge

Abstract: This work concentrates on the problem of watermarking embedding and blind optimum detection in full-frame DCT domain using channel-state knowledge concepts. Minimum length sequences are used to embed the watermark information in the color components. Each chip of the sequence is inserted in a random-like fashion in those coefficients that ensure imperceptibility, robustness and a very low probability of error in detection. As it will be shown the power of the watermark has to be distributed among the symbols not only considering imperceptibility but also to improve the detection process. Furthermore, two solutions are proposed to improve the robustness against cropping operations.

Digital broadcast receiver

Abstract: PROBLEM TO BE SOLVED: To provide a digital broadcast receiver that can display proper images, even when normal reproduction operation is disabled, right after the application of power and right after channel switching, at the reception of a digital television broadcast. SOLUTION: The digital broadcast receiver 10 is provided with a channel selection section 18a, that outputs image coding data VCDa to make a usual reproduction operation correspond to a channel selected by a user, a memory section 30 that outputs image coded data VCDb for a background reproduction operation, when the usual reproduction operation is disabled, a data selector 34 that receives the image coded data VCDa, VCDb and outputs either of them, and an MPEG video decode section 20 that decodes the image coded data outputted from the data selector 34 to generate an image signal. The channel selection section 18b sequentially receives each selected channel at a background, independently of the selection by the user and allows the memory section 30 to store the image coded data VCDb which correspond to each channel.

Method of embedding watermark into digital image

Abstract: Methods of embedding and detecting a watermark into/from a digital image are disclosed. A method of embedding a watermark in accordance with the present invention includes generating a predicted image of an original image by using a linear predictor; generating a difference image by subtracting said predicted image from said original image or vice versa; and segmenting said difference image into sub-regions. The method further includes the steps of calculating a watermark amplitude for each sub-region or for each pixel of each sub-region; performing a channel coding process on a set of watermark data bits; calculating a watermark block for each sub-region by using said encoded data bits, a pseudo random sequence (PRS) and said watermark amplitude; and embedding said watermark block into each sub-region by adding said watermark block with pixel values of each sub-region. As a result of the method described, the embedded information is robust against any modifications including loss data compression, filtering, channel noise, cropping, geometrical transformations, and etc.

BSS: a new approach for watermark attack

Abstract: Digital watermarking is an enabling technology to prove ownership on copyrighted material, detect originators of illegally made copies, monitor the usage of copyrighted multimedia data, and analyze the spread spectrum of data over networks and servers. Most watermarking methods for images and video can be viewed as a communications problem in which the watermark must be transmitted and received through a watermark channel. This channel includes distortions resulting from attacks and interference from the original digital data. It is well accepted that an effective watermarking scheme may be described as the secure, imperceptible, robust communication of information by direct embedding in, and retrieval from, digital data. For verifying the security and robustness of watermarking algorithms, specific attacks have to be applied to test them. By using a theoretical approach based on random processes, signal processes, and communication theory, we propose a stochastic formulation of a new watermarking attack using a blind source separation-based concept. The proposed attack considers the watermarking channel as a "black-box". A host image was passed through the "black-box", which includes the watermarking embedding process, and then the watermarked image was produced The watermarked image is viewed as linear mixtures of unknown source signals, and we attempt to recover sources from their linear mixtures without resorting to any prior knowledge by using blind source separation theory.

Stripe-based MSE control in image coding

Abstract: It is well known that compression of very large images (e.g. medical imaging, microscopy, satellite images) requires stripe-based or tiling processing. In some applications, the transmission of compressed data is performed through a rate constrained channel. Thus, rate allocation and control procedures have to be used to fit the channel characteristics. On the other hand, most applications require high quality image coding without any real time rate constraint (e.g. off-line compression for storage or for broadcasting over IP, ADSL, HDTV, etc.). Therefore, we propose a new stripe-based compression algorithm based on quality control. Our method computes first an optimal subband MSE allocation and then, the corresponding quantization steps. The proposed algorithm provides, both accurate local MSE control and a global rate-distortion improvement when compared to a rate constrained compression scheme. Furthermore, it performs better than JPEG2000.

Fluorescence spectrum estimation using multiple color images and minimum negativity constraint.

Abstract: An inexpensive method to convert a microscope into an imaging spectrometer is presented. Unlike current microscope-based spectrometers which use specialized optics or scanning mechanisms, our system only requires at most two image captures with a 3-chip CCD camera and a lightly-tinted color filter to output the color signal of a sample at each pixel. Basis spectra are obtained by principal components analysis applied to an ensemble of color signals of commercially-available dyes observed with different dichroic mirrors. A transformation matrix from channel values to spectral coefficients is derived. Minimum negativity constraint is applied to eliminate negative parts of the reconstructed fluorescence spectrum. The technique is demonstrated on fluorescence microspheres (fluorospheres) and chlorophyll from plant leaf.

Image processor for fluorescent observation

Abstract: PROBLEM TO BE SOLVED: To realize an image processor for fluorescent observation for obtaining an image in which a normal tissue is easily recognized from a lesioned tissue by simple constitution. SOLUTION: This image processor 4A comprises an image processing circuit 38 which assigns an image signal on a long wavelength side (a wavelength band including a non-absorption band of light of hemoglobin) of reflected light to a B channel of RGB channel, an image signal of a fluorescent image to a G channel, and an image signal on a short wavelength side (a wavelength band including an absorption band of light of hemoglobin) of the reflected light to an R channel, synthesizes them to be a single image to form a synthetic image, and which adjusts the gains of the three input image signals so that a boundary of hues of the normal tissue and the lesioned hue displayed on the synthetic image may be included in a range surrounded by four dots of (0.21, 0.53), (0.18, 0.50), (o.23, 0.44) and (o.25, 0.49) with respect to CIE 1976 UCS chromaticity diagram. COPYRIGHT: (C)2004,JPO

Image processing method and apparatus for multiple spectrum image data

Abstract: There are formed three kinds of virtual spectrum aperture images in which a weight is added to each spectrum channel image of multiple spectrum data, three kinds of characteristic virtual spectrum aperture images are allocated to RGB (red, green, blue) and a color synthesized image is displayed. A line spectrum image of a designated line of the displayed color synthesized image is displayed, and a spectrum of a designated point is further displayed. A user is able to select whether the spectrum that is once displayed should be left or deleted. When the displayed spectrum should be left, such displayed spectrum is superimposed upon a spectrum of the next selected point. Also, spectrums of points in the designated range are sequentially displayed in a cinema fashion.