Showing papers on "Grayscale published in 1992"

Color scales for image data

Abstract: Desirable properties of color scales are examined, and a linearized optimal color scale (LOCS) is introduced. The merits of color scales for medical image data were studied, and it was found that, in tests, although observers performed somewhat better with the newly developed LOCS than with the previously advocated heated-object color scale, they performed significantly better with a linearized gray scale than with either of the color scales. After evaluating these results, the authors suggest alternate solutions that might help observers perform better. Nonetheless, they believe that color scales can contribute to the perception of information in images. >

Multiscale contrast enhancement with applications to image fusion

Abstract: A method to merge images from different sensing modalities for visual display was introduced by Toet, van Ruyven, and Valeton in 1989, which produces a fused image by nonlinear recombination of the ratio of low-pass (R0LP) pyramidal decompositions ofthe original images. The appearance of merged images that are produced by this scheme is highly dependent on the contrast and mean gray level ofthe input images. That nonlinear multiplication of the successive layers of a ratio of low-pass pyramid results in a contrast-enhanced image representation that is highly invariant for changes in the global gray-level characteristics of the original image is shown. Application of this nonlinear multiplication procedure in the image fusion process results in composite images that appear highly independent of changes in lighting and gray-level gradients in the input images. The method is tested by merging different degraded versions of parallel registered thermal (FLIR) and visual (CCD) images.

Normalizing correlator for video processing

Abstract: A video image processor for generating an enhanced image of data based upon input gray scale picture element values of image data of a document background and printed information contained thereon generates a histogram of the gray scale picture element values for each tile of image data for an area of the document representing the frequency of occurrence of picture elements of a particular gray scale value. A correlator processes each histogram to determine a black reference level and a white reference level for each tile. Normalization factors are calculated based upon the black reference level and the white reference level. The input gray scale picture element values for each tile of the image data associated with the normalization factors of each tile are normalized based upon the normalization factors for each tile and correlated to generate a normalized and correlated representation of the image data.

Image processing system

Abstract: An image processing system for rapidly and efficiently converting a black and white image comprised of rows and columns of picture elements to a reduced size grayscale image wherein a dynamic determination is made of a specified number of picture elements from the black and white image which correspond to each new picture element within the reduced size grayscale image, a bit counting method is utilised to determine the number of black and white picture elements within each specified number of picture elements of the black and white image, the resultant tally being then utilised to access a table containing various grayscale values and the accessed grayscale value being assigned to an associated new picture element of the reduced size grayscale image.

Principled halftoning based on human vision models

Abstract: When models of human vision adequately measure the relative quality of candidate halftonings of an image, the problem of halftoning the image becomes equivalent to the search problem of finding a halftone that optimizes the quality metric. Because of the vast number of possible halftones, and the complexity of image quality measures, this principled approach has usually been put aside in favor of fast algorithms that seem to perform well. We find that the principled approach can lead to a range of useful halftoning algorithms, as we trade off speed for quality by varying the complexity of the quality measure and the thoroughness of the search. High quality halftones can be obtained reasonably quickly, for example, by using as a measure the vector length of the error image filtered by a contrast sensitivity function, and, as the search procedure, the sequential adjustment of individual pixels to improve the quality measure. If computational resources permit, simulated annealing can find nearly optimal solutions.

Image processing system

Abstract: An image processing system wherein for an inputted composite image composed of a line image and a dither image, both a line image processing and a dither image processing are carried out in parallel, and one of the processed results as selected in accordance with the image region discrimination result. The dither image processing is carried out through data conversion for calculating multivalued gray scale image from the inputted image data, gray scale data conversion for adjusting the gray scale image data so as to match an output device and obtaining such adjusted gray scale image data, and re-binarization for re-binarizing the gray scale image data after subjected to the gray scale conversion. The image region discrimination for discriminating if an image region is of a line image of a dither image is carried out based on a ratio of the number of black or white pixels within the region to the contour line length within the range. In ordered dither image through a screened type dither matrix is discriminated in accordance with a correlation between adjacent pixel trains each having a predetermined number of pixels.

3-dimensional sonographic analysis based on color flow Doppler and gray scale image data: a preliminary report.

Abstract: This paper presents preliminary results of a technique that permits acquisition and display of three-dimensional (3D) anatomy using data collected from color flow Doppler and gray scale image sonography. 3D sonographic image data were acquired as two-dimensional planar images with commercially available equipment. A translational stage permitted the transducer position and orientation to be determined. Color flow sonographic video image data were digitized into a PC-AT computer along with transducer position and orientation information. Color flow velocity and gray scale data were separated, 3D filtered, and thresholded. A surface rendering program was used to define the vessel blood-lumen interface. Planar slices of arbitrary orientation and volume rendered images were displayed interactively on a graphics workstation. The technique was demonstrated in a lamb kidney in vitro and for the carotid artery at the bifurcation in vivo. Our results demonstrate the potential of 3D sonography as a technique for visualization of anatomy. Color flow data offer direct access to the vascular system, facilitating 3D analysis and display. 3D sonography offers potential advantages over existing diagnostic studies in that it is noninvasive, requires no intravenous contrast material, offers arbitrary plane extraction and review after the patient has completed the examination, and permits vascular anatomy to be visualized clearly via rendered images.

Method and system for improved tone and color reproduction of electronic image on hard copy using a closed loop control

Abstract: A hard copy reproduction is formed of a video image which is an accurate reproduction of the tonal luminance differences and color of the video image. A gray scale and color test image is formed on the video monitor screen and measured using a photometer. The gray scale and color test image is reproduced on hard copy and may be measured using a densitometer. The two sets of measurements are entered into a computer system and used to adjust, on a pixel-by-pixel basis, the electronic controls of the hard color reproduction system to compensate for any deviations from accurate reproduction.

Morphological grayscale reconstruction: definition, efficient algorithm and applications in image analysis

Abstract: Gray-scale reconstruction is formally defined for discrete images A brief summary of the existing techniques to compute it is provided, and a hybrid algorithm that is an order of magnitude faster than any other algorithm is introduced Some of its application to image filtering and segmentation are listed >

Optimization of Hologram Computation for Real-Time Display

Abstract: Several methods of increasing the speed and simplicity of the computation of off-axis transmission holograms are presented, with applications to the real-time display of holographic images. A bipolar intensity approach enables a linear summation of interference fringes, a factor of two speed increase, and the elimination of image noise caused by object self- interference. An order of magnitude speed increase is obtained through the use of precomputed look-up tables containing a large array of elemental interference patterns corresponding to point source contributions from each of the possible locations in image space. Results achieved using a data-parallel supercomputer to compute horizontal-parallax- only holographic patterns containing 6 megasamples indicate that an image comprised of 10,000 points with arbitrary brightness (grayscale) can be computed in under one second.

Antialiasing apparatus and method for computer printers

Abstract: Printer apparatus provides a grayscale bitmap from a bitonal bitmap of desired output data. The apparatus includes a mapping function implemented as a lookup table for assigning predetermined grayscale values to bitonal bitmap pixels according to the neighborhood or subset of bitonal bitmap pixels including the subject pixel. From the grayscale values the laser of the laser printer is modulated to produce shades of gray during the printing of the desired data.

Dynamic thresholding system for documents using structural information of the documents

Abstract: Disclosed is a system that converts a scanned image of a complex document, wherein each pixel is represented by a gray scale level, into a bi-level image where text has been preserved and separated from the background. The system subdivides the scanned image into cells, and then creates histograms of the gray scale levels of the pixels in the cells. It creates matrices of the runs of dark pixels within the cells, and examines the runs to determine the extent of connected components. It computes the percentage of runs of each length, and computes the average gray scale level of runs of each length for the document image. It determines peaks in each of the histograms, and determines the width of the first peak within each histogram. The system uses this information to set a gray scale level threshold used to create the bi-level image.

One-dimensional least-squares model-based halftoning

Abstract: A least-squares model-based approach to digital halftoning is proposed. It exploits both a printer model and a model for visual perception. It obtains an optimal halftoned reproduction by minimizing the squared error between the response of the cascade of the printer and visual models to the binary image and the response of the visual model to the original gray-scale image. Least-squares model-based halftoning uses explicit eye models and relies on printer models that predict distortions and exploit them to increase, rather than decrease, both spatial and gray-scale resolution. The authors examine the one-dimensional case, in which each row or column of the image is halftoned independently. One-dimensional least-squares halftoning is implemented, in closed form, with the Viterbi algorithm. Experiments show that it produces better spatial and gray-scale resolution than conventional one-dimensional techniques and eliminates the problems associated with the modified (to account for printer distortions) error diffusion algorithm. >

Performance characteristics and image fidelity of gray-scale monitors.

Abstract: Gray-scale monitors are an essential element of electronic radiology, and their ability to provide images that are perceived to be identical to those available on conventional or laser-printed film is crucial to success of electronic radiology. Image fidelity is measured in physical characteristics (luminance, dynamic range, distortion, resolution, and noise) and with psychophysical techniques, including receiver operator characteristics analysis with clinical images and testing with contrast-detail patterns to determine threshold contrast. Currently, laser-printed images facilitate greater information transfer than does a gray-scale monitor because of their higher absolute luminance (500 ft-L vs 60 ft-L), greater perceived dynamic range, and better spatial resolution. In the near future, the developments of gray-scale monitors with 150-200 ft-L luminance, a display standard based on just noticeable differences, and algorithms to improve similarities between gray-scale display images and laser-printed ima...

Method for compressing, processing, and storing grayscale bitmaps

Abstract: A method for image processing includes the steps of scanning an image within a first grid of pixels, determining a grayscale value for each pixel scanned in the first grid of pixels, and, for each pixel scanned, activating a number of pixels of a second grid of pixels corresponding to the grayscale value determined. Data representing the second grid of pixels can be compressed, and stored for use in facsimile transmission or photoreprographic image production.

A new set of fast algorithms for mathematical morphology II: identification of topographic features on grayscale images

Abstract: New algorithms for morphological image processing are presented. These algorithms are based on recursive idempotent geodesic transforms using a pixel-dependent structuring element. Such transforms are used as building blocks to construct new, fast algorithms for the location of topographic features on grayscale images. This approach is first used for the location of regional extrema and then for watershed and water parting determination. The new algorithms are compared to previously known ones in terms of speed and results quality. The same basic transforms are also used to build evaluation tools for measuring the relative importance of watersheds and water partings. The usefulness of the new approach is illustrated by application examples on a biomedical image.

Consensus sync" data-sampling systems and methods

Abstract: Image processing systems and methods for retrieving digital data stored in a plurality of contiguous data cells on photographic film. An image sensor samples the image data at a plurality of pixel positions in each of the data cells and generates grayscale image data that is processed into a one-dimensional stream of binary pixels. A data sampling system processes the binary pixels by first selecting those binary pixels that correspond to the data cell centers. Then, a digital output signal is constructed from the selected pixels to represent the original data stored on the film. The stream of binary pixels are read in series. In particular, transitions, detected in the stream of binary pixels, are used to periodically estimate the data cell pitch and the transition phase. A plurality of, e.g. N, suggested distances from the current pixel to the next sampling point are located using the transition phases of the most recent N transitions. A preferred sampling phase is determined through a histogram to find a consensus among the N suggested distances. The digital output signal is constructed from those pixels that occur at the preferred sampling phase.

Line screen design for gray scale rendering

Abstract: A method and arrangement for reproducing an original image, includes scanning and digitizing an original image into pixels of a digitized image. The pixels of the digitized image are arranged into cells. A gray level halftone printer is then controlled to form dots along lines in accordance with at least a first template corresponding to increasing cell gray levels until a first line structure is stable. The printer is then controlled to form dots along lines in accordance with at least a second template corresponding to further increasing cell gray levels.

Optical morphological processors: gray scale with binary structuring elements, detection, and clutter reduction

Abstract: We consider morphological processing for clutter reduction and object detection. For detection, we compare a binary and gray-scale Hit-Miss Transform and find that the binary operator is preferable. For clutter reduction, we find gray-scale morphology to be preferable. We present a new gray-scale clutter reduction morphological algorithm for low clutter cases and a new algorithm for high clutter cases. In all morphological processing, we find binary structuring elements to be adequate; this is very attractive for our gray-scale morphology decomposition algorithm and its optical implementation.© (1992) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Apparatus for reproducing video signals on a monitor

Abstract: An apparatus for the reproduction of video signals on a monitor has a circuit connected with the monitor for the conversion of grayscale values of a video signal. The apparatus has a computing unit connected to the conversion circuit which, on the basis of a statistical evaluation of the grayscale distribution, recalculates the standard used for the conversion of the grayscale values so that in the display of an image on the monitor the dynamic range within a region of interest is completely utilized. The conversion circuit is supplied with the calculated, corrected values for the conversion from the calculating unit.

Rotation and gray-scale transform invariant texture recognition using hidden Markov model

Abstract: In the first stage of the proposed scheme the quadrature mirror filter (QMF) bank is used as the wavelet transform to decompose the texture image into subbands. Gray scale transform invariant features are then extracted from each subband image. In the second stage, the sequence of subbands is modeled as a hidden Markov model (HMM), and one HMM is designed for each class of textures. During recognition, the unknown texture is matched against all models. The best matched model identifies the texture class. The angles of rotation in the experiments are selected randomly in between -90 degrees and 90 degrees . Up to 95% classification accuracy is reported. >

Optical implementation of gray-scale morphology

Abstract: There is much work concerning morphological image processing, both binary and gray scale. Almost all implementations to date are performed electronically on standard computers, specialized processors, or specialized hardware. Prior work has described implementation of binary morphology on an optical processor, as well as indicating the relative merits of using an optical system. However, the restriction to binary morphology on an optical system has required that gray scale problems be reduced to binary morphology solutions using judiciously chosen binarization thresholds. This paper describes how gray scale morphology can be implemented on an optical correlator system using a threshold decomposition algorithm. A series of thresholded binary correlations are formed optically and summed on a CCD detector array or spatial light modulator, to produce the output morphologically processed gray scale image. The speed this optical system is much faster than 30 gray scale images per second. The details of the architecture used to implement threshold decomposition on an optical system is described, and issues relating to the implementation of binary morphology on an optical system are discussed. The threshold decomposition algorithm is discussed with attention to ways to reduce the number of intermediate processing steps required.

Medial description of gray-scale image structure by gradient-limited diffusion

Abstract: The representation of object shape in grayscale images is an important precursor to many common image interpretation needs, including recognition, registration, and measurement. Typically, such computer vision tasks have required the preliminary step of image segmentation, often via the detection of object edges. This paper presents a new means of describing grayscale object shape that obviates the need for edge-finding, i.e., classifying pixels as being inside or outside of an object boundary. Instead, this technique operates directly on the image intensity distribution to produce a set of `medialness' measurements at every pixel and across multiple spatial scales that capture more global properties of object shape. The application of an orientation-sensitive, gradient-limited diffusion model provides many of the benefits of global, multiscale structural analysis while preserving the local region- insulating effects of pixels having edge-like properties. The result of this procedure is a multiscale medial axis (MMA), which represents an object at multiple and simultaneous levels of scale, and which provides several desirable properties for describing the shape of grayscale forms.© (1992) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Resolution enhancement system for binary images

Abstract: An image processing system for providing edge enhancement of low resolution binary image files processes the low resolution bitmap data in sections or windows to determine whether an edge transition or "kink site" occurs within each window. The original bitmap data in the window is then replaced with edge enhanced gray scale data if a kink site is identified. The selection of the correct edge enhanced gray scale data to be used in place of the original bitmap data is based on whether the central pixel contained within the window is a black or white pixel, whether the central pixel is located on a single pixel line, and the location of the central pixel with respect to the kink site. The determination of whether the central pixel is a black or white pixel is based on the binary value assigned to the pixel, the determination of the location of the central pixel with respect to the kink site is based on pixel values and gradient magnitudes of surrounding pixel locations, and the determination of whether the central pixel is located on a single pixel line is based on the gradient magnitude of the central pixel and surrounding pixel locations.

Spatial nonlinearities of gray-scale CRT pixels

Abstract: We measured the overall luminance, the luminance profile of individual pixels, and the interactions among neighboring pixels of a grayscale (i.e., non-color) CRT, using a two- dimensional CCD camera. We find that the luminance of a pixel depends on the luminance of the two preceding pixels in the raster, and that the interaction results in superadditivity. Furthermore, the luminance of a pixel depends on the proportion of the screen illuminated. Two consequences of these nonlinearities are that average luminance (as in a halftone image) cannot be predicted from the linear summation of individual pixel spread functions, and that inverting the polarity of a display does not simply invert the luminance profiles. These interactions must be taken into account wherever the luminance profile of displayed stimuli is important.

A progressive scheme for digital image halftoning, coding of halftones, and reconstruction

Abstract: A digital halftoning technique for the efficient transformation of gray-scale images into bilevel ones, based on the progressive generation of the bilevel image pixels in a parallel way, is presented. An image distortion criterion, in which the gray-tone image is approximated by a filtered version of the halftoned image, is used for this purpose. A combined scheme is also derived in which continuous-tone images are progressively coded and transmitted in bilevel form and can be reconstructed in gray-scale form. >

Method and apparatus for imbedding controlled structure for gray scale rendering

Abstract: A method and arrangement for reproducing an original image has a scanner which scans and digitizes the original image into pixels, a controller coupled to the scanner to receive the digitized original image, and a printer coupled to the controller. The controller produces a first signal corresponding to a gray level halftoned representation of the digitized original image, and stabilizes the dots at specified pixels. The printer receives the first signal and reproduces the original image with stable dots at locations corresponding to the specified pixels.

Data field image compression

Abstract: A novel lossy image compression algorithm--nonuniform sampling and interpolation, or NSI--for fast uncompression on a low power compute platform is disclosed. Decoder simplicity is traded off for a slight (2.5 dB) signal to noise ratio degradation over a non-adaptive discrete cosine transform (DCT) and increased encoder complexity. Encoding is three times slower than the DCT. High quality images are obtained at compression rates as high as 8:1 for 8 bit per pixel greyscale images. NSI can uncompress an image 48 times faster than a DCT. This speed advantage is traded for a small degradation in quality and higher compressing complexity. However, the characteristics of NSI make it ideal for use in an application (a) where images are more often uncompressed than compressed and (b) where a PC will be decompressing the image without expensive hardware assistance.

Method and means for adding an extra dimension to sensor processed raster data using color encoding

Abstract: Many sensor information processing applications currently use monochrome B-scan presentations to exhibit processing results from radar, sonar, spectral estimation, seismic profiling, radio astronomy, bio-engineering, and infrared imaging. The use of color for such raster display presentations have been limited to the coding of amplitude values for a fixed set of hue/luminance colors to convey recognition by the human operator. Hue and luminance are used here independently to convey two orthogonal pieces of low signal-to-noise sensor information simultaneously to the operator for quick and accurate recognition. The net result is an added degree of freedom available on a single display surface, which not only improves operator recognition and reaction time for critical events, but precludes the necessity of a second display presentation for the alternate information and subsequent correlation of two data sets by visual comparison. This invention discloses a system to generate and add a new color dimension, a fourth orthogonal axis to the presented data, in addition to position and luminance levels of a video display. The process adds information independent of the usual gray scale as saturated colors on a monotonic wavelength scale from red to green to blue.

Gray-scale character recognition using boundary features

Abstract: Optical character recognition (OCR) traditionally applies to binary-valued imagery although text always scanned and stored in gray-scale. Binarization of multivalued image may remove important topological information from characters and introduce noise to character background. Low quality imagery, produced by poor print text and improper image lift, magnifies the shortcomings of this process. A character classifier is proposed to recognize gray-scale characters by extracting structural features from character outlines. A fast local contrast based gray-scale edge detector has been developed to locate character boundaries. A pixel is considered as an edge-pixel if its gray value is below a threshold and has a neighbor whose gray value is above the threshold. Edges are then thinned to one pixel wide. Extracting structural features from edges is performed by convolving the edges with a set of feature templates. Currently, 16 features, such as strokes, curves, and corners, are considered. Extracted features are compressed to form a binary vector with 576 features and it is used as input to a classifier. This approach is being tested on machine-printed characters which are extracted from mail address blocks. Characters are sampled at 300 ppi and quantized with 8 bits. Experimental results also demonstrate that recognition rates can be improved by enhancing image quality prior to boundary detection.© (1992) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.