Blur is an important attribute of human spatial vision, and sensitivity to blur has been the subject of considerable experimental research and theoretical modeling. Often these models have invoked specialized concepts or mechanisms, such as intrinsic blur, multiple channels, or blur estimation units. In this paper we review the several experimental studies of blur discrimination and find they are in broad empirical agreement. But contrary to previous modeling efforts, we find that the essential...
Topics: NASA Technical Reports Server (NTRS), BLURRING, VISUAL STIMULI, HUMAN FACTORS ENGINEERING, EYE...
The spatial standard observer is a computational model that provides a measure of the visibility of a target in a uniform background image or of the visual discriminability of two images. Standard observers have long been used in science and industry to quantify the discriminability of colors. Color standard observers address the spectral characteristics of visual stimuli, while the spatial standard observer (SSO), as its name indicates, addresses spatial characteristics. The SSO is based on a...
Topics: NASA Technical Reports Server (NTRS), VISUAL PERCEPTION, IMAGE CONTRAST, LUMINANCE, VISUAL STIMULI,...
Perimetric complexity is a measure of the complexity of binary pictures. It is defined as the sum of inside and outside perimeters of the foreground, squared, divided by the foreground area, divided by 4p . Difficulties arise when this definition is applied to digital images composed of binary pixels. In this paper we identify these problems and propose solutions. Perimetric complexity is often used as a measure of visual complexity, in which case it should take into account the limited...
Topics: NASA Technical Reports Server (NTRS), PHOTOGRAPHY, COMPLEXITY, DIGITAL SYSTEMS, VISION, PIXELS,...
To enhance the quality of the theatre experience, the film industry is interested in achieving higher frame rates for capture and display. In this talk I will describe the basic spatio-temporal sensitivities of human vision, and how they respond to the time sequence of static images that is fundamental to cinematic presentation.
Topics: NASA Technical Reports Server (NTRS), VISION, HUMAN BEINGS, MOTION PICTURES, CINEMATOGRAPHY,...
The present invention relates to devices and methods for the measurement and/or for the specification of the perceptual intensity of a visual image, or the perceptual distance between a pair of images. Grayscale test and reference images are processed to produce test and reference luminance images. A luminance filter function is convolved with the reference luminance image to produce a local mean luminance reference image. Test and reference contrast images are produced from the local mean...
Topics: NASA Technical Reports Server (NTRS), IMAGE CONTRAST, IMAGE PROCESSING, LUMINANCE, VISUAL...
A method for performing image compression that eliminates redundant and invisible image components is described. The image compression uses a Discrete Cosine Transform (DCT) and each DCT coefficient yielded by the transform is quantized by an entry in a quantization matrix which determines the perceived image quality and the bit rate of the image being compressed. The present invention adapts or customizes the quantization matrix to the image being compressed. The quantization matrix comprises...
Topics: NASA Technical Reports Server (NTRS), DATA COMPRESSION, DIGITAL TECHNIQUES, DISCRETE COSINE...
An alternative approach has been devised for encoding image data in compliance with JPEG 2000, the most recent still-image data-compression standard of the Joint Photographic Experts Group. Heretofore, JPEG 2000 encoding has been implemented by several related schemes classified as rate-based distortion-minimization encoding. In each of these schemes, the end user specifies a desired bit rate and the encoding algorithm strives to attain that rate while minimizing a mean squared error (MSE)....
Topics: NASA Technical Reports Server (NTRS), CODING, DATA COMPRESSION, OPTIMIZATION, MEAN SQUARE VALUES,...
Watson and Ahmuada (2005) constructed a Standard Spatial Observer (SSO) model for foveal luminance contrast signal detection based on the Medelfest data (Watson, 1999). Here we propose two changes to the model, dropping the oblique effect from the CSF and using the cone density data of Curcio et al. (1990) to estimate the variation of sensitivity with eccentricity. Dropping the complex images, and using medians to exclude outlier data points, the SSO model now accounts for essentially all the...
Topics: NASA Technical Reports Server (NTRS), LUMINANCE, SIGNAL DETECTION, NORMAL DENSITY FUNCTIONS,...
A Digital Video Quality (DVQ) apparatus and method that incorporate a model of human visual sensitivity to predict the visibility of artifacts. The DVQ method and apparatus are used for the evaluation of the visual quality of processed digital video sequences and for adaptively controlling the bit rate of the processed digital video sequences without compromising the visual quality. The DVQ apparatus minimizes the required amount of memory and computation. The input to the DVQ apparatus is a...
Topics: NASA Technical Reports Server (NTRS), DIGITAL TELEVISION, DISCRETE COSINE TRANSFORM, VIDEO...
Motion blur is a significant display property for which accurate, valid measurement methods are needed. Recent measurements of a set of eight displays by a set of six measurement devices provide an opportunity to evaluate techniques of measurement and of the analysis of those measurements.
Topics: NASA Technical Reports Server (NTRS), BLURRING, MOTION, DISPLAY DEVICES, VISUAL ACUITY, VISUAL...
Ideal methods are described for shrinking or expanding a discrete sequence, image, or image sequence. The methods are ideal in the sense that they preserve the frequency spectrum of the input up to the Nyquist limit of the input or output, whichever is smaller. Fast implementations that make use of the discrete Fourier transform or the discrete Hartley transform are described. The techniques lead to a new multiresolution image pyramid.
Topics: NASA Technical Reports Server (NTRS), DISCRETE FUNCTIONS, IMAGE PROCESSING, IMAGE RECONSTRUCTION,...
A major goal of the reseach group is to develop mathematical and computational models of early human vision. These models are valuable in the prediction of human performance, in the design of visual coding schemes and displays, and in robotic vision. To date researchers have models of retinal sampling, spatial processing in visual cortex, contrast sensitivity, and motion processing. Based on their models of early human vision, researchers developed several schemes for efficient coding and...
Topics: NASA Technical Reports Server (NTRS), CODING, COLOR VISION, COMPUTER VISION, IMAGE PROCESSING,...
A method for performing image compression that eliminates redundant and invisible image components is presented. The image compression uses a Discrete Cosine Transform (DCT) and each DCT coefficient yielded by the transform is quantized by an entry in a quantization matrix which determines the perceived image quality and the bit rate of the image being compressed. The present invention adapts or customizes the quantization matrix to the image being compressed. The quantization matrix comprises...
Topics: NASA Technical Reports Server (NTRS), DATA COMPRESSION, DIGITAL TECHNIQUES, DISCRETE COSINE...
The spatiotemporal power spectrum was calculated of 14 image sequences in order to determine the degree to which the spectra are separable in space and time, and to assess the validity of the commonly used exponential correlation model found in the literature. The spectrum was expanded by a Singular Value Decomposition into a sum of separable terms and an index was defined of spatiotemporal separability as the fraction of the signal energy that can be represented by the first (largest)...
Topics: NASA Technical Reports Server (NTRS), AUTOCORRELATION, IMAGE PROCESSING, MATHEMATICAL MODELS, POWER...
An image pyramid has been developed with basis functions that are orthogonal, self-similar, and localized in space, spatial frequency, orientation, and phase. The pyramid operates on a hexagonal sample lattice. The set of seven basis functions consist of three even high-pass kernels, three odd high-pass kernels, and one low-pass kernel. The three even kernels are identified when rotated by 60 or 120 deg, and likewise for the odd. The seven basis functions occupy a point and a hexagon of six...
Topics: NASA Technical Reports Server (NTRS), HEXAGONAL CELLS, IMAGE PROCESSING, LATTICES, ORTHOGONALITY,...
A method of measuring motion blur is disclosed comprising obtaining a moving edge temporal profile r(sub 1)(k) of an image of a high-contrast moving edge, calculating the masked local contrast m(sub1)(k) for r(sub 1)(k) and the masked local contrast m(sub 2)(k) for an ideal step edge waveform r(sub 2)(k) with the same amplitude as r(sub 1)(k), and calculating the measure or motion blur Psi as a difference function, The masked local contrasts are calculated using a set of convolution kernels...
Topics: NASA Technical Reports Server (NTRS), BLURRING, MOTION PERCEPTION, VISION, WAVEFORMS, PATENTS,...
A method for generating a visual acuity metric, based on wavefront aberrations (WFAs), associated with a test subject and representing classes of imperfections, such as defocus, astigmatism, coma and spherical aberrations, of the subject's visual system. The metric allows choices of different image template, can predict acuity for different target probabilities, can incorporate different and possibly subject-specific neural transfer functions, can predict acuity for different subject templates,...
Topics: NASA Technical Reports Server (NTRS), ABERRATION, PREDICTIONS, VISUAL ACUITY, WAVE FRONTS, OPTICAL...
A broad review is given of vision science and technology within NASA. The subject is defined and its applications in both NASA and the nation at large are noted. A survey of current NASA efforts is given, noting strengths and weaknesses of the NASA program.
Topics: NASA Technical Reports Server (NTRS), ARTIFICIAL INTELLIGENCE, COMPUTER VISION, CONFERENCES, IMAGE...
The discrete cosine transform (DCT) is widely used in image compression and is part of the JPEG and MPEG compression standards. The degree of compression and the amount of distortion in the decompressed image are controlled by the quantization of the transform coefficients. The standards do not specify how the DCT coefficients should be quantized. One approach is to set the quantization level for each coefficient so that the quantization error is near the threshold of visibility. Results from...
Topics: NASA Technical Reports Server (NTRS), COLOR CODING, DISCRETE COSINE TRANSFORM, IMAGE PROCESSING,...
A method is presented for performing color or grayscale image compression that eliminates redundant and invisible image components. The image compression uses a Discrete Cosine Transform (DCT) and each DCT coefficient yielded by the transform is quantized by an entry in a quantization matrix which determines the perceived image quality and the bit rate of the image being compressed. The quantization matrix comprises visual masking by luminance and contrast technique all resulting in a minimum...
Topics: NASA Technical Reports Server (NTRS), DATA COMPRESSION, DISCRETE COSINE TRANSFORM, PERCEPTUAL...
Processing of digital images destined for visual consumption raises many interesting questions regarding human visual sensitivity. This talk will survey some of these questions, including some that have been answered and some that have not. There will be an emphasis upon visual masking, and a distinction will be drawn between masking due to contrast gain control processes, and due to processes such as hypothesis testing, pattern recognition, and visual search.
Topics: NASA Technical Reports Server (NTRS), VISUAL PERCEPTION, IMAGING TECHNIQUES, DISPLAY DEVICES,...
Two types of research issues are involved in image management systems with space station applications: image processing research and image perception research. The image processing issues are the traditional ones of digitizing, coding, compressing, storing, analyzing, and displaying, but with a new emphasis on the constraints imposed by the human perceiver. Two image coding algorithms have been developed that may increase the efficiency of image management systems (IMS). Image perception...
Topics: NASA Technical Reports Server (NTRS), DATA MANAGEMENT, IMAGE PROCESSING, VISUAL PERCEPTION,...
This presentation describes how a vision model incorporating contrast sensitivity, contrast masking, and light adaptation is used to design visually optimal quantization matrices for Discrete Cosine Transform image compression. The Discrete Cosine Transform (DCT) underlies several image compression standards (JPEG, MPEG, H.261). The DCT is applied to 8x8 pixel blocks, and the resulting coefficients are quantized by division and rounding. The 8x8 'quantization matrix' of divisors determines the...
Topics: NASA Technical Reports Server (NTRS), BIT ERROR RATE, DISCRETE COSINE TRANSFORM, DISCRETE...
All vision systems, both human and machine, transform the spatial image into a coded representation. Particular codes may be optimized for efficiency or to extract useful image features. Researchers explored image codes based on primary visual cortex in man and other primates. Understanding these codes will advance the art in image coding, autonomous vision, and computational human factors. In cortex, imagery is coded by features that vary in size, orientation, and position. Researchers have...
Topics: NASA Technical Reports Server (NTRS), BRAIN, CODING, HUMAN FACTORS ENGINEERING, IMAGE PROCESSING,...
Modern electronic imaging systems include optics, sensors, sampling, noise, processing, compression, transmission and display elements, and are viewed by the human eye. Many of these elements cannot be assessed by traditional imaging system metrics such as the MTF. More complex metrics such as NVTherm do address these elements, but do so largely through parametric adjustment of an MTF-like metric. The parameters are adjusted through subjective testing of human observers identifying specific...
Topics: NASA Ames Research Center, Watson, Andrew B.
