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  • 1
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    Remote sensing of benthic microalgal biomass with a tower-mounted multispectral scanner (1980)
    Elsevier
    Details
    Publication Date: 1980-06-01
    Print ISSN: 0034-4257
    Electronic ISSN: 1879-0704
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by Elsevier
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  • 2
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    Comment [on “Spectrophotometric and color estimates of the Viking lander sites” by Friedrich O. Huck et al.] (1978)
    American Geophysical Union
    Details
    Publication Date: 1978-07-10
    Print ISSN: 0148-0227
    Electronic ISSN: 2156-2202
    Topics: Geosciences
    Published by American Geophysical Union
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  • 3
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    Spectrophotometric and color estimates of the Viking Lander sites (1977)
    American Geophysical Union
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    Publication Date: 1977-09-30
    Print ISSN: 0148-0227
    Electronic ISSN: 2156-2202
    Topics: Geosciences
    Published by American Geophysical Union
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  • 4
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    Some distinguishing characteristics of contour and texture phenomena in images (1992)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: The development of generalized contour/texture discrimination techniques is a central element necessary for machine vision recognition and interpretation of arbitrary images. Here, the visual perception of texture, selected studies of texture analysis in machine vision, and diverse small samples of contour and texture are all used to provide insights into the fundamental characteristics of contour and texture. From these, an experimental discrimination scheme is developed and tested on a battery of natural images. The visual perception of texture defined fine texture as a subclass which is interpreted as shading and is distinct from coarse figural similarity textures. Also, perception defined the smallest scale for contour/texture discrimination as eight to nine visual acuity units. Three contour/texture discrimination parameters were found to be moderately successful for this scale discrimination: (1) lightness change in a blurred version of the image, (2) change in lightness change in the original image, and (3) percent change in edge counts relative to local maximum.
    Keywords: COMPUTER PROGRAMMING AND SOFTWARE
    Type: In: Visual information processing; Proceedings of the Meeting, Orlando, FL, Apr. 20-22, 1992 (A93-32438 12-61); p. 55-67.
    Format: text
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  • 5
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    Isolating contour information from arbitrary images (1989)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Aspects of natural vision (physiological and perceptual) serve as a basis for attempting the development of a general processing scheme for contour extraction. Contour information is assumed to be central to visual recognition skills. While the scheme must be regarded as highly preliminary, initial results do compare favorably with the visual perception of structure. The scheme pays special attention to the construction of a smallest scale circular difference-of-Gaussian (DOG) convolution, calibration of multiscale edge detection thresholds with the visual perception of grayscale boundaries, and contour/texture discrimination methods derived from fundamental assumptions of connectivity and the characteristics of printed text. Contour information is required to fall between a minimum connectivity limit and maximum regional spatial density limit at each scale. Results support the idea that contour information, in images possessing good image quality, is (centered at about 10 cyc/deg and 30 cyc/deg). Further, lower spatial frequency channels appear to play a major role only in contour extraction from images with serious global image defects.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Visual Information Processing for Television and Telerobotics; p 177-190
    Format: application/pdf
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  • 6
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    Properties of a center/surround retinex. Part 2: Surround design (1995)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The last version of Edwin Land's retinex model for human vision's lightness and color constancy has been implemented. Previous research has established the mathematical foundations of Land's retinex but has not examined specific design issues and their effects on the properties of the retinex operation. We have sought to define a practical implementation of the retinex without particular concern for its validity as a model for human lightness and color perception. Here we describe issues involved in designing the surround function. We find that there is a trade-off between rendition and dynamic range compression that is governed by the surround space constant. Various functional forms for the retinex surround are evaluated and a Gaussian form is found to perform better than the inverse square suggested by Land. Preliminary testing led to the design of a Gaussian surround with a space constant of 80 pixels as a reasonable compromise between dynamic range compression and rendition.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: NASA-TM-110188 , NAS 1.15:110188
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  • 7
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    A discrepancy within primate spatial vision and its bearing on the definition of edge detection processes in machine vision (1990)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The visual perception of form information is considered to be based on the functioning of simple and complex neurons in the primate striate cortex. However, a review of the physiological data on these brain cells cannot be harmonized with either the perceptual spatial frequency performance of primates or the performance which is necessary for form perception in humans. This discrepancy together with recent interest in cortical-like and perceptual-like processing in image coding and machine vision prompted a series of image processing experiments intended to provide some definition of the selection of image operators. The experiments were aimed at determining operators which could be used to detect edges in a computational manner consistent with the visual perception of structure in images. Fundamental issues were the selection of size (peak spatial frequency) and circular versus oriented operators (or some combination). In a previous study, circular difference-of-Gaussian (DOG) operators, with peak spatial frequency responses at about 11 and 33 cyc/deg were found to capture the primary structural information in images. Here larger scale circular DOG operators were explored and led to severe loss of image structure and introduced spatial dislocations (due to blur) in structure which is not consistent with visual perception. Orientation sensitive operators (akin to one class of simple cortical neurons) introduced ambiguities of edge extent regardless of the scale of the operator. For machine vision schemes which are functionally similar to natural vision form perception, two circularly symmetric very high spatial frequency channels appear to be necessary and sufficient for a wide range of natural images. Such a machine vision scheme is most similar to the physiological performance of the primate lateral geniculate nucleus rather than the striate cortex.
    Keywords: CYBERNETICS
    Type: NASA-TM-102739 , NAS 1.15:102739
    Format: application/pdf
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  • 8
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    A Comparison of the Multiscale Retinex With Other Image Enhancement Techniques (1997)
    In:  CASI
    Details
    Publication Date: 2018-06-02
    Description: The multiscale retinex with color restoration (MSRCR) has shown itself to be a very versatile automatic image enhancement algorithm that simultaneously provides dynamic range compression, color constancy, and color rendition. A number of algorithms exist that provide one or more of these features, but not all. In this paper we compare the performance of the MSRCR with techniques that are widely used for image enhancement. Specifically, we compare the MSRCR with color adjustment methods such as gamma correction and gain/offset application, histogram modification techniques such as histogram equalization and manual histogram adjustment, and other more powerful techniques such as homomorphic filtering and 'burning and dodging'. The comparison is carried out by testing the suite of image enhancement methods on a set of diverse images. We find that though some of these techniques work well for some of these images, only the MSRCR performs universally well on the test set.
    Keywords: Instrumentation and Photography
    Format: application/pdf
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  • 9
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    Spatial vision processes: From the optical image to the symbolic structures of contour information (1988)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The significance of machine and natural vision is discussed together with the need for a general approach to image acquisition and processing aimed at recognition. An exploratory scheme is proposed which encompasses the definition of spatial primitives, intrinsic image properties and sampling, 2-D edge detection at the smallest scale, the construction of spatial primitives from edges, and the isolation of contour information from textural information. Concepts drawn from or suggested by natural vision at both perceptual and physiological levels are relied upon heavily to guide the development of the overall scheme. The scheme is intended to provide a larger context in which to place the emerging technology of detector array focal-plane processors. The approach differs from many recent efforts in edge detection and image coding by emphasizing smallest scale edge detection as a foundation for multi-scale symbolic processing while diminishing somewhat the importance of image convolutions with multi-scale edge operators. Cursory treatments of information theory illustrate that the direct application of this theory to structural information in images could not be realized.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: NASA-TP-2838 , L-16479 , NAS 1.60:2838
    Format: application/pdf
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  • 10
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    Modes of Visual Recognition and Perceptually Relevant Sketch-based Coding for Images (1991)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A review of visual recognition studies is used to define two levels of information requirements. These two levels are related to two primary subdivisions of the spatial frequency domain of images and reflect two distinct different physical properties of arbitrary scenes. In particular, pathologies in recognition due to cerebral dysfunction point to a more complete split into two major types of processing: high spatial frequency edge based recognition vs. low spatial frequency lightness (and color) based recognition. The former is more central and general while the latter is more specific and is necessary for certain special tasks. The two modes of recognition can also be distinguished on the basis of physical scene properties: the highly localized edges associated with reflectance and sharp topographic transitions vs. smooth topographic undulation. The extreme case of heavily abstracted images is pursued to gain an understanding of the minimal information required to support both modes of recognition. Here the intention is to define the semantic core of transmission. This central core of processing can then be fleshed out with additional image information and coding and rendering techniques.
    Keywords: CYBERNETICS
    Type: NASA-TM-104051 , NAS 1.15:104051
    Format: application/pdf
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