Showing papers on "Grayscale published in 1994"

A digital watermark

Abstract: The paper discusses the feasibility of coding an "undetectable" digital water mark on a standard 512/spl times/512 intensity image with an 8 bit gray scale. The watermark is capable of carrying such information as authentication or authorisation codes, or a legend essential for image interpretation. This capability is envisaged to find application in image tagging, copyright enforcement, counterfeit protection, and controlled access. Two methods of implementation are discussed. The first is based on bit plane manipulation of the LSB, which offers easy and rapid decoding. The second method utilises linear addition of the water mark to the image data, and is more difficult to decode, offering inherent security. This linearity property also allows some image processing, such as averaging, to take place on the image, without corrupting the water mark beyond recovery. Either method is potentially compatible with JPEG and MPEG processing. >

Rotation and gray scale transform invariant texture identification using wavelet decomposition and hidden Markov model

Abstract: In this correspondence, we have presented a rotation and gray scale transform invariant texture recognition scheme using the combination of quadrature mirror filter (QMF) bank and hidden Markov model (HMM). In the first stage, the QMF bank is used as the wavelet transform to decompose the texture image into subbands. The gray scale transform invariant features derived from the statistics based on first-order distribution of gray levels 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. The HMM is used to exploit the dependence among these subbands, and is able to capture the trend of changes caused by rotation. During recognition, the unknown texture is matched against all the models. The best matched model identifies the texture class. Up to 93.33% classification accuracy is reported. >

Method and apparatus for halftone rendering of a gray image using a blue noise mask

Abstract: A method of and system for rendering a halftone image of a gray scale image by utilizing a pixel-by-pixel comparison of the gray scale image against a blue noise mask is disclosed in which the gray scale image is scanned on a pixel-by-pixel basis and compared on a pixel-by-pixel basis to an array of corresponding data points contained in a blue noise mask stored in a PROM or computer memory in order to produce the desired halftoned image. Both digital and optically implemented halftone methods are disclosed. Application specific modifications of the blue noise mask as well as its use for producing halftoned color images are also disclosed.

Rotating non-rotationally symmetrical halftone dots for encoding embedded data in a hyperacuity printer

Abstract: A printing system for receiving grayscale input image data and rendering halftoned image data having embedded data on a recording medium includes an addressable three dimensional memory system. The memory system has a first set of address lines defining an x dimension, a second set of address lines defining a y dimension, and a third set of address lines providing an intensity dimension, and halftoning circuitry for receiving and transforming grayscale input image data into multi-bit value output data. A look-up table is used to match multi-bit value output data representing x dimension, y dimension, and intensity, to grayscale input image data. The system uses addressing circuitry for addressing the three dimensional memory system, with the first set of address lines and the second set of address lines defining a screen stored in the memory system, the first set of address lines and the second set of address lines providing x and y address values defined at a desired screen angle. Data is embedded in the halftone pattern by using rotation circuitry to modify the x and y address values as they are read from the look-up table. A modulating device receives this multi-bit value output data containing embedded data from the halftoning circuitry and converts it into modulated scan spots of defined intensity.

Error-diffused image compression using a binary-to-gray-scale decoder and predictive pruned tree-structured vector quantization

Abstract: The authors consider data compression of binary error diffused images. The original contribution is using nonlinear filters to decode error-diffused images to compress them in the gray-scale domain; this gives better image quality than directly compressing the binary images. Their method is of low computational complexity and can work with any halftoning algorithm. >

Color image segmentation by a watershed algorithm and region adjacency graph processing

Abstract: A new method for gray-scale, color and multispectral image segmentation is proposed. The method is based on a morphological split-and-merge fast watershed algorithm and region adjacency graph processing. It features partly iterative processing with relatively low computational load. Two system alternatives are presented and their application to color image segmentation is discussed. First computer simulations show correctness of operation and encourage for further research. >

Invariant image classification using triple-correlation-based neural networks

Abstract: Triple-correlation-based neural networks are introduced and used in this paper for invariant classification of 2D gray scale images. Third-order correlations of an image are appropriately clustered, in spatial or spectral domain, to generate an equivalent image representation that is invariant with respect to translation, rotation, and dilation. An efficient implementation scheme is also proposed, which is robust to distortions, insensitive to additive noise, and classifies the original image using adequate neural network architectures applied directly to 2D image representations. Third-order neural networks are shown to be a specific category of triple-correlation-based networks, applied either to binary or gray-scale images. A simulation study is given, which illustrates the theoretical developments, using synthetic and real image data. >

Grayscale printing system

Abstract: A system is provided for obtaining enhanced quality grayscale printing using standard printer architecture. An image to be printed is scanned to produce several bit maps for image pixels having different optical intensities. The different bit maps are handled by a standard print engine separately, in the same manner as multicolor bit maps would be handled. The image is then printed using a print head assembly having separate print heads for grayscale printing using different optical intensities. Thus, a printed image having enhanced resolution and quality, because of the optical intensity discrimination, is produced using a printer architecture which is the same as a standard multicolor printer architecture except for the front end, which scans for optical intensity, and the print head assembly, which has different print heads designed to produce different optical intensities. The print heads use either different ink dot sizes, inks having different pigment concentrations, or other suitable techniques for varying the optical intensity.

Fast Grayscale Granulometry Algorithms

Abstract: Granulometries constitute an extremely useful set of morphological operators, applicable to a variety of image analysis tasks. Traditional granulometry algorithms involve sequences of openings or closings of increasing size, and are therefore very slow on non-dedicated hardware. Efficient techniques have been proposed to compute granulometries in binary images, based on the concept of opening functions. In the present paper, a class of algorithms for computing granulometries in grayscale images is introduced. The most advanced among them are based on the new concept of opening tree. These algorithms are several orders of magnitude faster than traditional techniques, thereby opening up a range of new applications for grayscale granulometries.

Digital halftone rendering of a gray scale image with frequency-dependent diagonal correlation

Abstract: A method of halftoning a digital gray scale image is disclosed that utilizes a point by point thresholding comparison to a novel diagonal correlation dither matrix. The new dither matrix forces diagonal correlation of adjacent dots in the output image while maximizing dispersion of dots, thereby producing visually unobtrusive output dot patterns. The matrix is generated according to a spatial domain cost function that determines a cost value for each candidate pixel based on respective radial distances and relative angles between a candidate pixel and the ON pixels in the matrix such that unit diagonals are favored over placement of vertically or horizontally adjacent dots.

Hyperacuity printer architecture

Abstract: A hyperacuity printing system for rendering bitmapped image data on a photosensitive recording medium, the bitmapped image data being rendered as an array of pixels across the photosensitive recording medium in a fastscan direction, and an orthogonal slowscan direction. This system includes a data source for supplying grayscale input image data and a scanning device for rendering grayscale output image data onto the recording medium. The scanning device has a device for writing scan spots on the recording medium. Further included in this system is transformation circuitry for transforming the grayscale input image data into grayscale output image data. The transformation circuitry includes a halftoner, a thresholder, and a selection device, where the selection device selects either the thresholder or the halftoner to provide the grayscale output image data. Finally, included is a modulating device coupled between the transformation circuitry and the scanning device for intensity modulating each of the scan spots in accordance with the grayscale output image data.

Graphics system for displaying images in gray-scale

Abstract: A graphics system for use with a computer in a gray-scale mode. The graphics system utilizes a lookup table having index values to be stored in a frame buffer. The lookup table is addressed by convening color information, such as RGB color information, to a luminance value, which is then used to access the table. The index values may be used to index a second lookup table for providing luminance information. The present invention further discloses methods of insuring index values provided by the lookup table closely approximate the desired luminance value within the available gray-scale space. Further, the present invention provides methods for performing arithmetic transfer operations on gray-scales represented by indices in the frame buffer.

Halftoning in a hyperacuity printer

Abstract: A hyperacuity printing system for rendering halftoned image data on a recording medium. The system includes comprising a data source for supplying grayscale input image data and a writing device for writing grayscale output image data onto the recording medium. Also included is halftoning circuitry for transforming the grayscale input image data into the grayscale output image data, the halftoning circuitry including a lookup table for providing the grayscale output image data described as halftone dots arranged as a continuum from a lowest intensity value to a highest intensity value of the grayscale input image data. Finally, included is a modulating device coupled between the halftoning circuitry and the writing device for converting the grayscale output image data from the halftoning circuitry into a form which can be utilized by the writing device.

Perceptual coding of images for halftone display

Abstract: The authors present a new technique for coding gray-scale images for facsimile transmission and printing on a laser printer. They use a gray-scale image encoder so that it is only at the receiver that the image is converted to a binary pattern and printed. The conventional approach is to transmit the image in halftoned form, using entropy coding (e.g., CCITT Group 3 or JBIG). The main advantages of the new approach are that one can get higher compression rates and that the receiver can tune the halftoning process to the particular printer. They use a perceptually based subband coding approach. It uses a perceptual masking model that was empirically derived for printed images using a specific printer and halftoning technique. In particular, they used a 300 dots/inch write-black laser printer and a standard halftoning scheme ("classical") for that resolution. For nearly transparent coding of gray-scale images, the proposed technique requires lower rates than the standard facsimile techniques. >

Identifying an area of interest using histogram data arranged in predetermined sequence

Abstract: A method for automatic analysis and enhancement of digitized images to identify the area of interest (AOI) from background areas divides a digitized image into a number of regions, and calculates histograms of gray scale or density for each region. An image of the regions in histogram space is created according to a selected sequence of the regions, chosen to preserve spatial proximity. This image is then processed by peak detection to identify features grouped spatially and by similarity of histograms. From this the AOI is identified, and the contrast enhancement is applied to the original image, according to the characteristics of the output device. The method is particularly adapted for enhancing medical X-ray images, for output to viewing devices.

Hand shape extraction from a sequence of digitized gray-scale images

Abstract: Gesture recognition is currently a major trend in human-computer interface researches. In a gestural interface, the extraction of the hand shape from a digitized scene is the first step before the analysis and recognition of the gestures themselves. Aiming at the implementation of a gestural interface, in this paper the authors present a method to extract fingertip coordinates from a sequence of images. The authors propose a method comprising histogram analysis, using the results from movement detection in order to find threshold values, and applying gray level slicing. This overall processing solves some problems found in conventional methods, such as the influence of shadows. A potential application would be in the implementation of an input device that substitutes the mouse. >

Compression of gray-scale fingerprint images

Abstract: The FBI has developed a specification for the compression of gray-scale fingerprint images to support paperless identification services within the criminal justice community. The algorithm is based on a scalar quantization of a discrete wavelet transform decomposition of the images, followed by zero run encoding and Huffman encoding.

Precise visual inspection for LSI wafer patterns using subpixel image alignment

Abstract: This paper reports on an image processing algorithm and hardware for fast, precise inspection of LSI wafer patterns. In order to detect deep sub-micron defects such as 0.2 /spl mu/m at high speed by grayscale image comparison, we must overcome the sampling errors that inevitably occur between two images during detection. For this purpose, we have developed a subpixel image alignment algorithm that infers the correct sampling position and creates the two resampled images with subpixel accuracy. We have also developed an 8-channel pipelined processor with gate arrays. It has 8/spl times/19,000 gates and can operate at 8/spl times/15 MHz. Evaluation of the system confirmed that the accuracy of the subpixel image alignment was 0.16 pixels or less and that the inspection system could detect 0.18 /spl mu/m defects at a pixel size of 0.25 /spl mu/m for half-micron LSI wafer patterns with an inspection speed of 25 s/cm/sup 2/. >

Global threshold method and apparatus

Abstract: The problem of thresholding is considered from a clustering point of view and a novel weight-based clustering method (WCThresh) is implemented in a neural network image processor 50. The neural network image processor 50 uses weights 51-53, representing clusters of gray scale pixels of an image of document 43, to provide a threshold for the image of document 43. The processor 50 modifies weights 51-53 with the input pixels and comparator 60 using a nearest value criterion to provide the threshold.

Multiple tonal range image processing system

Abstract: A host computer converts an entered gray scale image into a raster image expressing multiple tonal ranges, using an intermediate spot pattern determined in advance. Here, the intermediate spot pattern is a spot pattern composed of pixels which can take only binary value densities with information indicating tonal ranges embedded in the manner of arrangement of the pixels in the spot pattern. Therefore, this raster image logically expresses a large number of tonal ranges which cannot be actually expressed with pixels in binary value densities. A printer receives this raster image from the host computer and converts the intermediate spot pattern in this raster image into an output spot pattern which can assume tertiary values or more in density, thereby printing out a half-tone image actually expressing multiple tonal ranges.

Embedded active surfaces for volume visualization

Abstract: We propose a new technique for use in the visualization of sparse, fuzzy, or noisy 3D data This technique incorporates the methods of deformable or active models that have been developed in 2D computer vision In this paper we generalize such models to 3D in a manner that is both practical and mathematically elegant, and we thereby avoid many of the problems associated with previous attempts to generalize deformable models When generalizing to 3D, deformable models have several drawbacks-- including their acute sensitivity to topology, parameterization, and initial conditions--which limit their effectiveness Many of these problems stem from the underlying parameterization of the model This paper presents an implicit representation of deformable models The implicit representation is an embedding of objects as level sets of grayscale functions which serve as templates The evolution equation associated with the energy minimization process for a model has an analogous partial differential equation which governs the behavior of the corresponding grayscale template We show that the 'active blobs' associated with the embedding of active models have several useful properties First, they are topologically flexible Second, grayscale images represent families of models Third, when surfaces are embedded as grayscale images, they are described by a natural scale space This scale space provides the ability to solve these equations in a multi-scale manner Several 2D examples of technique are presented, as well as some visualization results from 3D ultrasound© (1994) COPYRIGHT SPIE--The International Society for Optical Engineering Downloading of the abstract is permitted for personal use only

A Database for Handwritten Text Recognition Research Some of the criticisms of experimental pattern recognition that are related to the replication of experiments and the comparison

Abstract: SUMMARY AND CONCLUSION The image database discussed in this correspondence addresses several important aspects not covered by most other data sets. Only images scanned from mailpieces in a working post office are included. This overcomes the subject-bias problems of other databases that were scanned in laboratory settings. Also, the data were. scanned at 300 pixels/in in 8-bit grayscale. This allows for experimentation with preprocessing and grayscale recognition techniques. The image files are compressed with a public domain difference coding algorithm. The bi-tonal images are stored as l-bit/pixel. Complete C language source is provided for the difference coding algorithm and a routine to convert the l-bit/pixel data I-byte/pixel format. Imager Digitizer The context that can be provided by a restricted domain was also All the images were scanned on an Eikonix EC850 4096x4096 addressed in the design of the database. The inclusion of cities, CCD digitizer.

Three dimensional anisotropy contrast magnetic resonance imaging

Abstract: A method for contrast magnetic resonance imaging (MRI) based on three axial anisotropic diffusion weighted images (DWIs) of the identical imaging plane. Three primary colors, red, green, and blue, are first assigned to the gray scale of the three axial, x-, y-, z-axis, anisotropic DWIs. These three primary color images are then vectorially combined to form a single image in full visible color spectrum. Since the sum of the three primary colors of the same intensity results in cancellation (white out), the process effectively eliminates the background signals from isotropic water motion. Accordingly, each pixel of the final color image exhibits a color of a unique frequency, according to the balance of red, green, and blue, reflecting direction of anisotropic water motion in space. Water motion in neuronal fibers, especially those in axons, possesses high intravoxel anisotropy compared to other elements of the nervous system. Therefore, the method is especially sensitive for discerning axonal direction and density.

A fast implementation of 1-D grayscale morphological filters

Abstract: This paper presents an algorithm for the fast implementation of 1-D grayscale morphological filters with set structuring elements. The algorithm is developed by filter property analysis, instead of by architecture design. It performs an opening or closing with a single pass procedure. The average number of operations required is less than three comparisons per sample for openings and closings, which is independent of the size of the structuring element used. >

Method and apparatus for dither array generation to reduce artifacts in halftoned images

Abstract: An existing void-and-cluster method for generating dither arrays for halftoning grayscale images on binary printing devices is improved by including additional steps which both homogenize the starting pattern used in the void-and-cluster method and correct the starting pattern for the effects of oversized dots generated by the printing devices. More particularly, a constant gray starting pattern is first subjected to an error diffusion halftoning process before void and cluster processing to produce a starting binary pattern as a more homogeneous starting point. In addition, after the starting binary pattern has been created, it can be modified to take into account that most printers print "oversized dots" in order to avoid white areas between dots. In particular, from the starting binary pattern, a starting gray pattern is created which uses oversized dot information to assign grayscale values to the "0" pixels surrounding a "1" pixel. Then cluster-finding and void-finding filters are used on both the starting binary pattern and the starting gray pattern to locate "clusters" and "voids". Pixels are transferred from the clusters to the voids to homogenize the arrays and generate an initial binary pattern and an initial gray pattern. The initial binary pattern and the initial gray pattern are then used to assign threshold values to the dither array.

Quadrature shape detection using the flow integration transform

Abstract: A transform, the Flow Integration Transform (FIT), is applied for determining the presence of a preconceived shape in a gray scale image. The FIT represents a form of Quadrature Shape Detection. The expected contour serves as a filter for detecting potential targets as periodic signals. The FIT performs a line integral of two vectors: (1) the flow, a vector equal to the gradient of the image's intensity but rotated by 90 degrees, and (2) the local tangent to the path of integration. The path of integration follows the expected contour. The integration is performed starting at each point in the image, producing a two-dimensional transform whose pixel value corresponds to the relative presence of the contour at that location in the input image. The transform exhibits the feature that information widely dispersed in the image becomes concentrated in a local area of the transform.

System and method for picture image processing employing transformation of picture data

Abstract: A method of picture image processing, and system for carrying out same, involves generation of a composite mapping function, for transforming gray scale values to different values in order to enhance contrast. A reduced range histogram is generated, involving removing a percentage of the total histogram counts from bottom and top sub-ranges and also removing spikes. The reduced histogram is then density averaged in order to obtain a first map function. A second map function is generated for interfacing with the characteristics of the printer to be used, and a composite mapping transform is generated by combining the two generated functions. After the composite mapping function is generated, each gray value of the image data set is transformed in accordance with the composite function, for use in printing, thereby providing an enhanced contrast image.

Restorer: a visualization technique for handling missing data

Abstract: Pseudocoloring is a frequently used technique in scientific visualization for mapping a color to a data value. When using pseudocolor and animation to visualize data that contain missing regions displayed as black or transparent, the missing regions popping in and out can distract the viewer from the more relevant information. Filling these gaps with interpolated data could lead to a misinterpretation of the data. The paper presents a method for combining pseudocoloring and grayscale in the same colormap. Valid data are mapped to colors in the colormap. The luminance values of the colors bounding areas of missing data are used in interpolating over these regions. The missing data are mapped to the grayscale portion of the colormap. This approach has the advantages of eliminating distracting gaps caused by missing data and distinguishing between those areas that represent valid data and those areas that do not. This approach was inspired by a technique used in the restoration of paintings. >