Showing papers on "Edge enhancement published in 1995"

Wavelets and image fusion

Abstract: As new remote sensing systems are deployed, we will see an increase in the amount of image data available at different wavelengths. Also, images from a single sensor over the same area often exhibit clouds, forcing analysts to switch among several images or to mosaic the images by manually defining cutlines to eliminate clouds. The ability to fuse multiple images over the same area, and to have the fused product exhibit, in a single image, the important details visible in individual bands has become crucial in dealing with the large volume of data available. We describe an approach to image fusion using the wavelet transform. When images are merged in wavelet space, we can process different frequency ranges differently. For example, high frequency information from one image can be combined with lower frequency information from another, for performing edge enhancement. We have built a prototype system that allows experimentation with various wavelet array combination and manipulation methods for image fusion, using a set of basic operations on wavelet frequency blocks. Problems caused by image misregistration and processing artifacts are described. Examples of wavelet fusion results are shown, along with test images that clarify behavior of the wavelet fusion methods used.© (1995) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Image encoding and decoding method and apparatus using edge synthesis and inverse wavelet transform

Abstract: A digitized image is encoded by detecting edges in the image, encoding the position and sharpness of the detected edges, filtering the image by a low-pass filter to generate a low-frequency image, and encoding the low-frequency image. A digitized image encoded in this way is reconstructed by generating a horizontal edge image and a vertical edge image from the encoded edge position and sharpness information, synthesizing a pair of high-frequency images by filtering the horizontal and vertical edge images with an edge synthesis filter, decoding the low-frequency image, and performing an inverse wavelet transform on the decoded low-frequency image and the high-frequency images.

Automated license plate locator and reader including perspective distortion correction

Abstract: An automated license plate locator and reader (10) which provides novel methods for 1) correcting for perspective distortion (16), 2) locating the license plate (20), 3) reading the license plate (22) and 4) improving the confidence rating of the output signal (228) The novel method for accommodating a wide range of viewing geometries involves warping the image to eliminate perspective distortion of the plate resulting from roadside camera placement The novel method for locating plates involves correlating an "idealized" edge template of a license plate with an edge-enhanced version of the image Edge enhancement and shadow reduction is achieved by applying a Laplacian operator over the input image Performance is further improved by filtering out distracting edges within the resulting correlation surface and then locating the highest peaks within this filtered correlation surface The location of the highest peaks provides the location of the plate The novel method for reading the license plates involves performing a modified binary correlation of an image of the plate with reference characters to provide output signals indicative of the symbols on the plate This output is correlated with valid license plate signals to improve the confidence rating thereof

Edge enhancement system for ultrasound images

Abstract: A method for enhancing an ultrasound image The image is assumed to be in the form of an ordered array of pixels Each pixel corresponding to the intensity of the echo generated by a corresponding voxel in an ultrasound energy field Axial and lateral directions relative to the ultrasound beam used to generate the sound field are defined within the ordered array The method of the present invention includes the steps of dividing the image into a plurality of processing blocks, picking blocks that satisfy certain statistical constraints for edge enhancement, enhancing the pixels in the selected blocks, and then displaying the pixels in each block, whether enhanced or not, that are above a display threshold for the block in question The statistical constraints are determined by second order statistics with reference to the axial and later directions In one embodiment of the present invention, sum and difference histograms are used to approximate the second order statistics, thereby reducing the computational load

Controller for medical image review station

Abstract: A medical image review station has several functions with visual feedback which are controlled by a controller. These functions include detail/real-time mode; density, contrast and edge enhancement image appearance characteristics; zoom; cine loop; single frame jog; skip forward/back; displayed frame speed and direction; still print; cancel; directory.

Method and apparatus for binary-encoding image data using error diffusion with edge enhancement

Abstract: An image processing system for displaying pixel data on a screen performs a binary-encoding method using error diffusion with edge enhancement. In the method for binary-encoding the image data, pixels to be binary-encoded are divided into normal and edge regions, and the pixel data is binary-encoded in accordance with the divided regions. By using the method, bars on the display screen which are unpleasant to the eye can be removed and an image with good edge sharpness can be obtained.

Efficient algorithm for the detection of parabolic curves

Abstract: A new approach for parabolic curve detection is presented based on Hough transforms. This approach uses the vertices of the curve as the detecting parameters which also indicate the position of the maximum curvature. Evidence for the transformation is gathered from the edge gradient obtained from an edge enhancement operator. The Sobel operator is used for edge enhancement. For the detection of parabolic curves in any orientation, a coordinate transformation matrix is used to derive a new parabolic equation which involves the edge gradient information. In the proposed algorithm, parabolic curves in any orientation are detected by using a 3D accumulator array. The new algorithm, therefore reduces the accumulator size from 4D accumulator array if an ordinary Hough transform for parabola detection is used. The reduced parameter space of the proposed algorithm improves the processing time and decreases storage requirement for the detection of parabolic curves. The paper reports on the accuracy obtained when this approach is used on natural and synthetic images containing parabolic and other curves.

Resolution enhancement system for combined binary and gray scale halftone images

Abstract: A system for performing edge enhancement of mixed low resolution image files employs a binarization and sorting unit to sort data that is indicative of binary data from the mixed low resolution image input file. The sorted binary data is then supplied to a binary data edge enhancement processor for edge enhancement processing. The output from the binary data edge enhancement processor unit is supplied to a data merger unit along with the original image data. The data merger unit determines whether the original image data was part of a gray-scale image. If the data merger determines the original data is part of a gray-scale image, the original data is supplied as the output of the processing system. If the data merger determines that the original data is binary image data, the output from the binary edge enhancement processor unit is supplied as the output of the processing system.

Invariance of edges and corners under mean-curvature diffusions of images

Abstract: We have recently proposed the use of geometry in image processing by representing an image as a surface in 3-space. The linear variations in intensity (edges) were shown to have a nondivergent surface normal. Exploiting this feature we introduced a nonlinear adaptive filter that only averages the divergence in the direction of the surface normal. This led to an inhomogeneous diffusion (ID) that averages the mean curvature of the surface, rendering edges invariant while removing noise. This mean curvature diffusion (MCD) when applied to an isolated edge imbedded in additive Gaussian noise results in complete noise removal and edge enhancement with the edge location left intact. In this paper we introduce a new filter that will render corners (two intersecting edges), as well as edges, invariant to the diffusion process. Because many edges in images are not isolated the corner model better represents the image than the edge model. For this reason, this new filtering technique, while encompassing MCD, also outperforms it when applied to images. Many applications will benefit from this geometrical interpretation of image processing, and those discussed in this paper include image noise removal, edge and/or corner detection and enhancement, and perceptually transparent coding.

Rank-order and morphological enhancement of image details with an optoelectronic processor

Abstract: In all-optical processors, enhancement of image details is the result of high-pass filtering. We describe an optoelectronic processor in which detail enhancement results from the digitally calculated difference between an original input image and its low-pass filtered version. The low-pass filtering is realized through the rank-order median and the morphological opening and closing operations calculated by use of the optical convolver. It is shown that the normalized difference between the morphological white and black top hats enhances bright and dark image details analogously to the rank-order unsharp masking.

Precomputing and encoding compressed image enhancement instructions

Abstract: Traditional techniques such as filtering and edge enhancement have been applied to restoring images that have been distorted due to lossy image compression. However, these techniques have ignored a unique feature that can be exploited when working with digital compression. Before the image is stored or transmitted, the sender has access to both the original and the distorted images, enabling the encoder to transmit information specifying the regions where the enhancement was successful. To utilize this feature, before storage or transmission the sender produces a codec file, and assesses the efficacy of one or more enhancement schemes. To determine which image regions have been improved by the enhancement, the enhanced codec is compared to the original. A map of where the enhancement scheme was successful is encoded into the image by making tiny adjustments to the image itself. This method can comply with many compression standards, adds nothing to the compressed images' bandwidth, and distorts the image by only a very tiny amount. Examples are presented showing the reduction of distortion if enhancement is used, together with calculations of how much distortion is introduced if a standard decompressor is used.

Edge enhancement, contrast reversal and logic operations using beam fanning in a photorefractive iron-doped barium titanate crystal

Abstract: We investigate the dynamics of beam fanning in a photorefractive barium titanate crystal at different wavelengths and with a mixed-polarization state of the input beam. The investigations reveal a remarkable difference in the behaviours at different wavelengths. This is further used to advantage for edge enhancement and image intensity inversion processes. Incoherent erasure to control the beam fanning has been exploited to perform some of the logic operations. The simplified geometry, ease of alignment and low input intensities involved are some features of the present work.

Center-surround filters for the detection of small targets in cluttered multispectral imagery: background and filter design

Abstract: Center-surround (CS) fields have long been identified in the human visual system as having properties of edge enhancement that facilitate the detection, location, and tracking of small objects. Unfortunately, the automatic digital implementation of such capabilities is not straightforward, since digital computers lack the neural functionality and connectivity inherent in the retina, optic chiasm, geniculate nuclei, and visual cortex. In this paper, we discuss efficient techniques for implementing CS detectors in terms of a class of nonlinear filters. In particular, we emphasize image enhancement schemes that cue the registration of CS detectors over the target, thus rendering our filters implementationally feasible in terms of hit rate and computational cost. Examples are given of the CS detectors that we call the adaptive Double- Gated and Triple-Gated filters (DGF and TGF). Such filters account for spatial nonstationary input. We further show how the DGF and TGF are useful for object detection in multispectral imagery. Analyses emphasize error and computational cost in practical sensing scenarios.

Real-time image processing with a cat conjugator

Abstract: We demonstrate the real-time image-processing operations of edge enhancement, theta filtering, and pattern recognition with a self-pumped phase conjugator with an external erase beam to modify the index gratings formed inside the photorefractive BaTiO3 crystal.

The resel-based GIS

Abstract: There now exist several microcomputer processing systems which incorporate algorithms and display techniques appropriate for the class of objects known as images Zooming, histogram equalization, contrast stretching, ratioing, edge enhancement, and filtering are common options used in these systems In the present discussion a system is proposed for the equivalent processing of general resolution elements (resells), instead of the homogeneous picture elements (pixels) which are found in image processing systems The resel processing system requires a new, generalized, repertoire of processing algorithms and a high resolution display A summary is provided of the facilities and procedures required, a computational metaphor using computer spreadsheets is described, and the applicability to censels (census data elements) and to medical data is suggested

Edge behavior of error diffusion

Abstract: Error diffusion is an important technique for digital halftoning. One of the most observable artifacts of error diffusion is the inherent edge enhancement. We analyze the edge behavior of error diffusion. We show that error diffusion does not always enhance edges. For some error diffusion weights, it actually blurs the images. We demonstrate that the source for edge enhancement or blurring is the nonuniform distribution of the correction terms. We propose an enhancement index to predict the overall edge behavior for a given set of weights.

ROC-Analyse zur Bildnachverarbeitung digitaler Thoraxaufnahmen

Abstract: PURPOSE To examine the extent to which digital luminescence radiography (DLR) can be used for the imaging of pulmonary nodules and interstitial lung disease in chest radiography without any loss of image quality. Additionally: to examine whether post-processing of image data can optimise the recognizability of varied image details. MATERIALS AND METHODS Detail perceptibility studies were performed on an anthropomorphic thorax phantom with simulated nodules and small linear and reticular details. Under standard conditions, digital luminescence radiographs were obtained in 7 different image modes, and these were compared with a 200-speed screen-film system. The detection of these systems was evaluated in an ROC analysis on the basis of 19,200 individual observations. RESULTS Edge enhancement or application of high-frequency-enhancing small filter kernels (S 5) slightly improves the detection of linear structures; however, the illustration of nodular details is markedly reduced. Larger filter kernels (S 20, S 40) make a definitive detection possible--not only of circular, but also of linear details. CONCLUSIONS Storage phosphor radiographs are equal to the tested analog screen-film-system. The optimization of post-processing can be helpful in the prevention of routine multiple documentations.

Fuzzy approach for smoothing and edge detection in color images

Abstract: Edge detection is one of the most important image processing steps towards image understanding. The resultant isolated regions or segments must be completely separated from their neighbors; that is, edges be continuous. Images must first be smoothed to remove noises. In this paper, a novel fuzzy smoother algorithm is presented which removes all camera noises and enhances edge contrasts. A fuzzy edge detection algorithm is then presented which is applied on the smoothed image. In this algorithm normalized hue in HSI and color contrast in RGB spaces are combined using an aggregate operator. Almost local maxima is then found for all edge directions and the results are combined. Finding another local maxima produces promising results.© (1995) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Edge enhancement to improve visualizations of tube/line placement in x-ray imaging

Abstract: A nonlinear unsharp masking algorithm designed specifically to improve visualization of tube and line placements in chest x-ray imaging is presented in this paper. This algorithm was incorporated as an on-demand button in the design of a PACS display console. To address the concerns of radiologists about the artifacts accompanying image processing operations, we utilized a window-shade display scheme that shows both processed and unprocessed images simultaneously in the same display window at full resolution. We have found that the new algorithm enhances more details in low contrast areas without more over-shootings at high contrast edges. This algorithm is beneficial to tube/line placement examinations since the tips of tubes and lines are typically located in the areas of high brightness and low contrast. Preliminary results indicate that our modified unsharp masking algorithm as an option in a PACS workstation leads to better visualizations of tube-placement position for MICU physicians.© (1995) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

[ROC analysis of image quality in digital luminescence radiography in comparison with current film-screen systems in mammography]

Abstract: Aim To compare in mammography the image quality of digital luminescence radiography (DLR) to that of usual film screen mammography and xeromammography. Materials and methods Three single emulsion film-screen combinations, one double coated high resolution film and xeroradiography, were tested for this purpose. In our phantom study the detectability of microcalcifications, fibrils and low contrast details were first of all studied separately. Image processing techniques were, for example, contrast variation by grey scale level windowing, "unsharp mask" filtering and regulatable edge enhancement. Phantom images were made and then the image quality was evaluated by observer performance study using a receiver operating characteristic (ROC analysis). Results Best results in respect of detection of microcalcifications and fibrils were found in xeroradiography, luminescent image plate and double-coated film-screen combination. These systems showed more favourable ROC curves than the single emulsion film-screen combinations. Conclusions Our results indicate that image quality of digital images in the field of image processing is equal to that of conventional mammographic techniques and partially superior to detection of low contrast details.

Unsharp masking and its inverse processing integrated in a compression/decompression scheme: application to cardiac angiograms

Abstract: Image data compression can be useful for storage or transmission of cardiac angiograms In clinical systems, images are recorded in a `raw' format, and are usually processed with an edge enhancement filter to improve the visibility of medical information The raw images are needed for other processing including quantitative measurements, and their enhanced version is used for display We report on a compression scheme based on full-frame DCT which allows the integration of enhancement in the codec We investigated whether the raw or the enhanced image should be compressed We studied an inverse filter and integrated it in the decompression process, so that a non-enhanced image can be derived after enhancement and compression The de-enhancement filter acts as a low pass filter for the quantization noise We proposed to improve the inverse filter using a regularized signal restoration technique

Extended permutation filters and their application to edge enhancement

Abstract: Extended permutation (EP) filters are defined and analyzed in this paper. In particular, we focus on extended permutation rank selection (EPRS) filters. These filters are constrained to output an order statistic from an extended observation vector. This extended vector includes N observation samples and K statistics that are functions of the observation samples. By selecting an appropriate extended observation space, we show that the EPRS filters can be designed to have excellent edge enhancement characteristics. Moreover, the EPRS filters can perform edge enhancement in the presence of noise making them a powerful filter class.

New edge-enhanced error diffusion based on the error sum criteria

Abstract: In this paper, a new edge enhanced error diffusion algorithm which is based on the Eschbach's algorithm is proposed. Thick edge artifacts with large edge enhancing factor as well as less edge enhancement effects for the bright or dark pixel values are observed in the previous algorithm. By analyzing the phenomena, a new improved algorithm is proposed by using the diffused error sum and input pixel value. An input pixel is classified into a normal- or edge-region pixel based on the error sum criteria. Then, a new error calculation is employed for the edge-region pixel, while conventional error calculation is used for the normal- region pixel. The proposed method requires only a few additional calculations, and provides edge enhanced binary output images. The edge is less influenced by the brightness offset and thick edge artifacts are reduces.

Extended permutation filters and their application to image edge enhancement

Abstract: Extended permutation (EP) filters are defined and analyzed in this paper. In particular, we focus on extended permutation rank selection (EPRS) filters. These filters are constrained to output an order statistic from an extended observation vector. This extended vector includes N observation samples and K statistics that are functions of the observation samples. By selecting an appropriate extended observation space, we show that the EPRS filters can be designed to have excellent edge enhancement characteristics. Moreover, the EPRS filters contain several previously defined edge enhancing filters as a subset and can perform edge enhancement in the presence of noise.

Cellular Neural Networks for Image Deconvolution and Enhancement: A Microscopy Toolkit

Abstract: A new microscopy image processing environment is shown, using several novel algorithms of Cellular Neural Networks (CNN). 3D and 2D deblurring, diffusion-based edge enhancement, morphological operations and texture segmentations are the main parts of the system. Since custom CNN VLSI chips are near to be released, we show the theoretical background how to use these analogue image processing parallel supercomputers for microscopy. We have developed a hardware-software system for complete problem-solving in microscopic environment by CNN. Theoretical results and examples are shown by using real-life microscopic multilayer images and natural textures.