Registration is a fundamental task in image processing used to match two or more pictures taken, for example, at different times, from different sensors, or from different viewpoints. Virtually all large systems which evaluate images require the registration of images, or a closely related operation, as an intermediate step. Specific examples of systems where image registration is a significant component include matching a target with a real-time image of a scene for target recognition, monitoring global land usage using satellite images, matching stereo images to recover shape for autonomous navigation, and aligning images from different medical modalities for diagnosis.Over the years, a broad range of techniques has been developed for various types of data and problems. These techniques have been independently studied for several different applications, resulting in a large body of research. This paper organizes this material by establishing the relationship between the variations in the images and the type of registration techniques which can most appropriately be applied. Three major types of variations are distinguished. The first type are the variations due to the differences in acquisition which cause the images to be misaligned. To register images, a spatial transformation is found which will remove these variations. The class of transformations which must be searched to find the optimal transformation is determined by knowledge about the variations of this type. The transformation class in turn influences the general technique that should be taken. The second type of variations are those which are also due to differences in acquisition, but cannot be modeled easily such as lighting and atmospheric conditions. This type usually effects intensity values, but they may also be spatial, such as perspective distortions. The third type of variations are differences in the images that are of interest such as object movements, growths, or other scene changes. Variations of the second and third type are not directly removed by registration, but they make registration more difficult since an exact match is no longer possible. In particular, it is critical that variations of the third type are not removed. Knowledge about the characteristics of each type of variation effect the choice of feature space, similarity measure, search space, and search strategy which will make up the final technique. All registration techniques can be viewed as different combinations of these choices. This framework is useful for understanding the merits and relationships between the wide variety of existing techniques and for assisting in the selection of the most suitable technique for a specific problem.

A survey of image registration techniques

Let's read! We will often find out this sentence everywhere. When still being a kid, mom used to order us to always read, so did the teacher. Some books are fully read in a week and we need the obligation to support reading. What about now? Do you still love reading? Is reading only for you who have obligation? Absolutely not! We here offer you a new book enPDFd the perception of the visual world to read.

The Perception of the Visual World. By James J. Gibson. U.S.A.: Houghton Mifflin Company, 1950 (George Allen & Unwin, Ltd., London). Price 35s.

There are declines with age in speed of processing, working memory, inhibitory function, and long-term memory, as well as decreases in brain structure size and white matter integrity. In the face of these decreases, functional imaging studies have demonstrated, somewhat surprisingly, reliable increases in prefrontal activation. To account for these joint phenomena, we propose the scaffolding theory of aging and cognition (STAC). STAC provides an integrative view of the aging mind, suggesting that pervasive increased frontal activation with age is a marker of an adaptive brain that engages in compensatory scaffolding in response to the challenges posed by declining neural structures and function. Scaffolding is a normal process present across the lifespan that involves use and development of complementary, alternative neural circuits to achieve a particular cognitive goal. Scaffolding is protective of cognitive function in the aging brain, and available evidence suggests that the ability to use this mechanism is strengthened by cognitive engagement, exercise, and low levels of default network engagement.

/pdf/the-adaptive-brain-aging-and-neurocognitive-scaffolding-3igyn72710.pdf

The Adaptive Brain: Aging and Neurocognitive Scaffolding

A classic photographic task is the mapping of the potentially high dynamic range of real world luminances to the low dynamic range of the photographic print. This tone reproduction problem is also faced by computer graphics practitioners who map digital images to a low dynamic range print or screen. The work presented in this paper leverages the time-tested techniques of photographic practice to develop a new tone reproduction operator. In particular, we use and extend the techniques developed by Ansel Adams to deal with digital images. The resulting algorithm is simple and produces good results for a wide variety of images.

/pdf/photographic-tone-reproduction-for-digital-images-k89wmpv97f.pdf

Photographic tone reproduction for digital images

Blood vessels usually have poor local contrast, and the application of existing edge detection algorithms yield results which are not satisfactory. An operator for feature extraction based on the optical and spatial properties of objects to be recognized is introduced. The gray-level profile of the cross section of a blood vessel is approximated by a Gaussian-shaped curve. The concept of matched filter detection of signals is used to detect piecewise linear segments of blood vessels in these images. Twelve different templates that are used to search for vessel segments along all possible directions are constructed. Various issues related to the implementation of these matched filters are discussed. The results are compared to those obtained with other methods. >

/pdf/detection-of-blood-vessels-in-retinal-images-using-two-2lxvrugvz5.pdf

Detection of blood vessels in retinal images using two-dimensional matched filters

Background
The image formed by the eye's optics is blurred by the ocular aberrations, specific to each eye. Recent studies demonstrated that the eye is adapted to the level of blur produced by the high order aberrations (HOA). We examined whether visual coding is also adapted to the orientation of the natural HOA of the eye.

https://dash.harvard.edu/bitstream/handle/1/11855837/3743894.pdf?sequence=1

Using pattern classification to measure adaptation to the orientation of high order aberrations.

Measuring preferences for moving video quality is harder than for static images due to
the fleeting and variable nature of moving video. Subjective preferences for image
quality can be tested by observers indicating their preference for one image over another.
Such pairwise comparisons can be analyzed using Thurstone scaling (Farrell, 1999).
Thurstone (1927) scaling is widely used in applied psychology, marketing, food tasting
and advertising research. Thurstone analysis constructs an arbitrary perceptual scale for
the items that are compared (e.g. enhancement levels). However, Thurstone scaling does
not determine the statistical significance of the differences between items on that
perceptual scale. Recent papers have provided inferential statistical methods that produce
an outcome similar to Thurstone scaling (Lipovetsky and Conklin, 2004). Here, we
demonstrate that binary logistic regression can analyze preferences for enhanced video.

Statistical analysis of subjective preferences for video enhancement

BACKGROUND As text is magnified, the number of letters that can be displayed with a magnifier or other reading aid at any one time (window size) reduced. There is a great deal of evidence that reading rates increase as the number of letters displayed increases. The minimum number of proportionally spaced letters necessary to read at maximal rates from a scroll display, in which the text is continuously panned across a television screen, is not known. METHODS Visually impaired (VI)and normally sighted (NA) observers were asked to read either sentences or random words scrolled across a computer screen. The window size was varied so that from one to 12 characters were visible, on average, at any one time. Each subject read with six different window sizes within the range of one to 12 characters visible. RESULTS For the NA group, a window of four to five characters was necessary to read at maximal rates. VI subjects, as a group, required a significantly larger window of six to seven characters to reach maximal reading rates. CONCLUSIONS The window size requirement for the NA group is close to the size other investigators have reported for a fixed-width font However, the VI group required a larger window than did the NA group, which has not been previously reported. This requirement could result from the additional stimulation available with a larger window to entrain the eyes' motion when reading from a passively scrolled display. low vision, reading rates, scroll display, computer screen, window size

Visually impaired observers require a larger window than normally sighted observers to read from a scroll display.

Hazard detection with a monocular bioptic telescope

Recent studies have reported that flanking stimuli broaden the psychometric function and lower detection thresholds. In the present study, we measured psychometric functions for detection and discrimination with and without flankers to investigate whether these effects occur throughout the contrast continuum. Our results confirm that lower detection thresholds with flankers are accompanied by broader psychometric functions. Psychometric functions for discrimination reveal that discrimination thresholds with and without flankers are similar across standard levels, and that the broadening of psychometric functions with flankers disappears as standard contrast increases, to the point that psychometric functions at high standard levels are virtually identical with or without flankers. Threshold-versus-contrast (TvC) curves with flankers only differ from TvC curves without flankers in occasional shallower dippers and lower branches on the left of the dipper, but they run virtually superimposed at high standard levels. We discuss differences between our results and other results in the literature, and how they are likely attributed to the differential vulnerability of alternative psychophysical procedures to the effects of presentation order. We show that different models of flanker facilitation can fit the data equally well, which stresses that succeeding at fitting a model does not validate it in any sense.

/pdf/psychometric-functions-for-detection-and-discrimination-with-mu4t1qua3b.pdf

Eli Peli

Papers

Using pattern classification to measure adaptation to the orientation of high order aberrations.

Statistical analysis of subjective preferences for video enhancement

Visually impaired observers require a larger window than normally sighted observers to read from a scroll display.

Hazard detection with a monocular bioptic telescope

Psychometric functions for detection and discrimination with and without flankers