Pairs Of Digital Images Research Articles

Experimental evidence that primate trichromacy is well suited for detecting primate social colour signals.

Primate trichromatic colour vision has been hypothesized to be well tuned for detecting variation in facial coloration, which could be due to selection on either signal wavelengths or the sensitivities of the photoreceptors themselves. We provide one of the first empirical tests of this idea by asking whether, when compared with other visual systems, the information obtained through primate trichromatic vision confers an improved ability to detect the changes in facial colour that female macaque monkeys exhibit when they are proceptive. We presented pairs of digital images of faces of the same monkey to human observers and asked them to select the proceptive face. We tested images that simulated what would be seen by common catarrhine trichromatic vision, two additional trichromatic conditions and three dichromatic conditions. Performance under conditions of common catarrhine trichromacy, and trichromacy with narrowly separated LM cone pigments (common in female platyrrhines), was better than for evenly spaced trichromacy or for any of the dichromatic conditions. These results suggest that primate trichromatic colour vision confers excellent ability to detect meaningful variation in primate face colour. This is consistent with the hypothesis that social information detection has acted on either primate signal spectral reflectance or photoreceptor spectral tuning, or both.

Sequence discrimination of heterogeneous crossing of seal impression and ink-printed text using adhesive tapes

This paper presents a technique to discriminate the sequence of stamped seal impression and ink-printed text in a document to detect falsely signed documents. In many Asian countries where a seal is widely used to endorse documents, a possibly forged document involves a seal impressed before the text is printed. The proposed method uses adhesive tapes with peel adhesion strength of approximately 25oz/in. to exfoliate the top layer of the overlapping region of seal impression and ink-printed text in the document. A pair of digital images of the overlapping region, captured using an infinite focus microscope, is compared for color changes before and after the exfoliation with adhesive tapes. The proposed sequence discrimination index (SDI) measures the amount of color changes before and after the exfoliation to determine the sequence of seal impression and printed text. Experiment results show that the SDI successfully discriminates the sequence of seal impression and printed text for different types of ink cartridges and seal inkpads under various storage conditions, enabling forensic investigation of falsely signed documents with a seal.

Nearness of Covering Uniformities: Theory and Application in Image Analysis

This paper applies the concepts of proximity and uniform spaces in an image processing (IP) application (Isbell, Uniform spaces, vol 12, American Mathematical Society, Providence, 1964; Di Concilio, Beyond Topology, AMS Contemporary Mathematics, vol. 486, Amer. Math. Soc. pp. 89–114, 2009). Application of these mathematical concepts to a digital image space and considering the time constraint of IP applications requires some modifications to the actual definitions. The paper presents a method to find a nearness measure between images based on these concepts. Given a pair of digital images, the basic approach starts with the approximation of the covering uniformity (\({\hat{\mathcal{C}}}\)) of the first image and then restricts the search on the second image based on proximities between the elements of \({\hat{\mathcal{C}}}\) and descriptive neighborhoods in the second image. This work carries forward the basic approach to descriptively near sets from the work by J.F. Peters and S.A. Naimpally (Notices Amer. Math. Soc, vol. 59(4), pp. 536–542, 2012).

Fracture of sandstone characterized by digital image correlation

Evaluation of mode I fracture characteristics, such as critical opening displacement and process-zone length, is fundamental for the analysis and prediction of crack growth. To identify deformation with micron-scale resolution, experiments were performed using digital image correlation, where displacement is determined through a comparison of a pair of digital images by matching a small area from the image before deformation to the image after deformation. The matching process uses a cross-correlation algorithm, and within this study, the correlation is based on a Fast Fourier Transform method. Mode I fracture tests were performed on Berea sandstone using three-point bending. Twelve specimens, of three types, were fabricated: six center notch (0.5mm radius), three smooth boundary, and three reduced-section (6 or 12mm radius notch). The characteristics of tensile fracture, namely opening displacement and crack length, were extracted from detailed displacement measurements. At the onset of unstable propagation (peak load) for the center notch specimens, the critical opening displacement ωc=30μm at the notch tip, and as the crack propagated, the known position of ωc allowed the identification of the process zone throughout the post-peak response. Incremental displacement contours established the tip of the effective crack, and the length of the process zone lp=5–7mm, about 10 times the maximum grain size. In addition, it was observed that the process zone maintained a constant length with constant critical opening for all tests.

3D discrete rotations using hinge angles

In this paper, we study 3D rotations on grid points computed by using only integers. For that purpose, we investigate the intersection between the 3D half-grid and the rotation plane. From this intersection, we define 3D hinge angles which determine a transit of a grid point from a voxel to its adjacent voxel during the rotation. Then, we give a method to sort all 3D hinge angles with integer computations. The study of 3D hinge angles allows us to design a 3D discrete rotation and to estimate the rotation between a pair of digital images in correspondence.

Image quality in conventional chest radiography. Evaluation using the postprocessing tool Diamond View ®

The objective of this work was to evaluate the influence of the postprocessing tool Diamond View ® (Siemens AG Medical Solutions, Germany) on image quality in conventional chest radiography. Evaluation of image quality remains a challenge in conventional radiography. Based on the European Commission quality criteria we evaluated the improvement of image quality when applying the new postprocessing tool Diamond View ® (Siemens AG Medical solutions, Germany) to conventional chest radiographs. Three different readers prospectively evaluated 102 digital image pairs of chest radiographs. Statistical analysis was performed with a p value <0.05 considered as significant. Images were evaluated on basis of the modified imaging Quality Criteria by the Commission of the European Communities. Each of the 11 image quality criteria was evaluated separately using a five point classification. Statistical analysis showed an overall tendency for improved image quality for Diamond View ® (DV) for all criteria. Significant differences could be found in most of the criteria. In conclusion DV improves image quality in conventional chest radiographs.

Image quality in conventional lumbar spine radiography: Evaluation using the post-processing tool Diamond View ®

Conventional radiography contributes for the majority of examinations in radiology departments. Based on the European Commission Quality Criteria we evaluated the effects on image quality when applying the new post-processing tool Diamond View ® (Siemens AG Medical Solutions, Germany) to conventional lumbar spine radiographs. 100 digital image pairs in two directions in two planes of lumbar spine radiographs were prospectively evaluated by two radiologists. Statistical analysis was performed with a p-value < .05 considered as significant. Images were evaluated on basis of the modified imaging Quality Criteria by the Commission of the European Communities, rated on a five-point scale. Statistical analysis showed an overall tendency for improved image quality of Diamond View ® (DV) for all criteria. Significant differences could be found in most of the criteria. Additional phantom analyses supported the advantage of DV. In conclusion DV improves image quality in conventional lumbar spine radiographs.

Comparison of Digital and Film Stereo Photography of the Optic Nerve in the Evaluation of Patients with Glaucoma

The aim of this study was to validate a digital simultaneous stereo photography system against film in the assessment of optic nerve head features in patients with glaucoma. Fifteen digital and 15 corresponding film simultaneous stereo photographs (SSP) of the optic nerve from patients with glaucoma were graded by two glaucoma specialists. Assessed parameters included the vertical and horizontal cup-to-disc ratios (VCD and HCD, respectively), and the image quality score (1 = worse, 5 = best) for each image. Digital and film SSP were presented in random order, two times to each grader. A total of 60 evaluations (30 digital and 30 film) per grader were collected. A Nidek 3-Dx simultaneous stereo disc camera (Gamagori, Japan) was used with both a standard 35-mm-film camera back, and with a 6.1 mega pixel camera (Nikon D1x, Tokyo, Japan) for capture of digital images. All digital images were stored on a computer and reviewed using the Navis Screener software (proprietary software from Nidek). Digital image pairs were evaluated directly on an ADVAN 27-inch Liquid Crystal Display computer monitor (Taipei, Taiwan) with resolution comparable to that of the digital camera, using the screen-vu stereo viewer held at a fixed angle to the monitor. Film image pairs were evaluated using a Pentax stereo slide viewer (Asahi Optical Co., Tokyo, Japan) illuminated by a light box over a neutral density filter to match the luminance between the computer screen and the light box. The mean difference between digital and film was near zero for all three evaluated outcomes (VCD, HCD, and quality score), and there was no significant grader effect for any of the outcomes. Digital images correlated well with film for SSP of the optic nerve in glaucoma.

EXTRAÇÃO SEMI-AUTOMÁTICA DE RODOVIAS EM UM PAR DE IMAGENS AÉREAS DIGITAIS UTILIZANDO GEOMETRIA EPIPOLAR E PROGRAMAÇÃO DINÂMICA

The purpose of this paper is to introduce a methodology for semi-automatic road extraction from aerial digital image pairs by using dynamic programming and epipolar geometry. The method uses both images from where each road feature pair is extracted. The operator identifies the corresponding road features and s/he selects sparse seed points along them. After all road pairs have been extracted, epipolar geometry is applied to determine the automatic point-to-point correspondence between each correspondent feature. Finally, each correspondent road pair is georeferenced by photogrammetric intersection. Experiments were made with rural aerial images. The results led to the conclusion that the methodology is robust and efficient, even in the presence of shadows of trees and buildings or other irregularities.

Registration of digital retinal images using landmark correspondence by expectation maximization

A method for registering pairs of digital images of the retina is presented, using a small set of intrinsic control points whose matching is not known. Control point matching is then achieved by calculating similarity transformation (ST) coefficients for all possible combinations of control point pairs. The cluster of coefficients associated with the matched control point pairs is identified by calculating the Euclidean distance between each set of ST coefficients and its Rth nearest neighbour, followed by use of the Expectation–Maximization (EM) algorithm. Registration is then achieved using linear regression to optimize similarity, bilinear or second order polynomial transformations for the matching control point pairs. Results are presented of (a) the cross-modal image registration of an optical image and a fluorescein angiogram, (b) temporal registration of two images of an infant eye, and (c) mono-modal registration of a set of seven standard field optical photographs. For cross-modal registration, using a set of independent matched control points, points are mapped with an estimated accuracy of 2.9 pixels for 575×480 pixel images. Bilinear and second-order polynomial transformation models all prove to be appropriate for the final registration transform.

Array-projection geometry and depth discrimination with Tuned-Aperture Computed Tomography for assessing the relationship between tooth roots and the inferior alveolar canal

Objectives: The purpose of this study is to compare Tuned-Aperture Computed Tomography (TACT) image sets made with linear vertical, linear horizontal, conical, and x-shaped x-ray projection arrays with regard to observer accuracy in (1) measuring the distance from the apex of a tooth root to the middle of the inferior alveolar canal (IAC), (2) measuring the shortest distance from the surface of a tooth root to the surface of the IAC, and (3) determining whether the root is buccal or lingual to the IAC. The same relationships were also examined by means of pairs of images and the buccal object rule. Study Design: Two artificial mandible sections with simulated IACs were fabricated. The same human mandibular premolar root was used in both models to prevent development of learning cues to differentiate between models. The models were imaged from both sides, resulting in 4 orientations. An optical bench was designed to precisely orient different beam projection arrays for production of TACT image sets and pairs of images for use with the buccal object rule. Twelve dentists participated as observers to independently assess the relationships between the tooth root and the IAC with regard to the 4 orientations. Results: For measuring the distance from the tooth apex to the middle of the IAC, TACT image sets made from conical and x-shaped arrays proved significantly more accurate than TACT image sets made from linear vertical or linear horizontal projections or pairs of digital images used with the buccal object rule (P < .05). For measuring the shortest distance between the tooth surface and the IAC surface, TACT image sets made from linear vertical, conical, and x-shaped projection arrays were significantly more accurate than measurements made through use of the buccal object rule or TACT image sets made through use of a linear horizontal projection array (P < .05). The following percentages of mistakes were made in determining whether the tooth root was buccal or lingual to the IAC: buccal object rule (58%), linear horizontal array (31%), linear vertical array (2%), conical array (0%), and x-shaped array (0%). Conclusions: For TACT, images acquired with conical and x-shaped beam projection arrays are preferred to those acquired with linear arrays for assessing the relationship between tooth roots and the IAC. TACT was found to be significantly more accurate than standard application of the buccal object rule for the relationships investigated. (Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2001;91:252-9)

Side-scan sonar image processing using thin plate splines and control point matching

The development of reliable software tools to aid human interpretation of complex digital images is of increasing importance. In particular, change detection requires that two or more images be carefully overlaid (registered) using digital techniques that compensate for picture distortions caused by sensor motion, ambient conditions, etc. We are primarily interested in small scale changes that occur in a given underwater scene observed at different times. In this paper we describe our use of thin plate splines in registering pairs of digital images composed of millions of pixels. We also review work on selecting and matching the control points needed for image registration.

Effects of variations in the duration of diffusible-tracer infusions on calculated values of global and local cerebral blood flow.

Using dual tracer quantitative digital autoradiography and iodoantipyrine (IAP), we compared local cerebral blood flow (LCBF) measurements using two different infusion times within the same animal. Rats were given concurrent infusions of 14C-IAP and 123I-IAP; one tracer was administered over 20 seconds and the other over 40 seconds. Pairs of autoradiograms, one representing predominantly 123I and the other 14C, were then produced from 20 micron-thick brain sections and images from each section were digitized and processed to produce pairs of digital images of LCBF. The corresponding LCBF images were compared quantitatively on a pixel-by-pixel basis. Global LCBF values were greater (28%) at 20 seconds compared to 40 seconds, consistent with the previously reported "falling flow" phenomenon. Perhaps more importantly, the actual pattern of LCBF differed in certain regions such as the cortex, hippocampus, thalamus, and cerebellum between the two time points. In other words, the quantitative patterns of calculated LCBF values were dependent upon the duration of tracer infusion, even when the infusion times were kept below recommended limits (45 seconds). Thus, errors in LCBF measurements may occur in certain structures even in brief experiments. Because these errors are spatially dependent rather than blood flow dependent, there is presently no model which can be globally applied to the brain to correct them.

The evaluation of a crosscorrelation pattern recognition technique for flow visualization

A method based on crosscorrelation of synthesized digital image pairs has been used for determination of velocity vector fields associated with fluid flow about a cylinder. A simple model has been used to test the validity of this image-processing technique for replacement of the time-consuming manual evaluation of time-sequenced photographs used for flow visualization. A time-sequenced digital image pair was synthesized by using the standard equations of motion of fluid flow about a cylinder. Both optimum particle density and time delay for the best performance of the algorithm were found.

Digital mobile radiography

A storage phosphor digital imaging system has been used to perform virtually all of an increasing number of mobile (portable) projectional roentgenographic examinations in a busy hospital. Approximately 130 such studies are done per day, of which about 110 are chest examinations. The processing unit suffices to keep pace with peak activity in the radiology department. This technique has decreased the repeat rate for portable anteroposterior chest radiographic examinations from 4.5% to less than 1% and has resulted in an even more dramatic reduction in the rate for lateral or decubitus chest examinations as well as for studies of the abdomen and those done in the operating room. The diagnostic accuracy and confidence level achieved in interpreting the complementary pair of digital images has been equivalent to or has exceeded that obtained with conventional mobile analog film-screen radiographs.

Stereographic Observations from Geosynchronous Satellites: An Important New Tool for the Atmospheric Sciences

The capability of making stereographic observations of clouds and their temporal changes from two simultaneously scanning geosynchronous satellites is a new basic meteorological analysis tool with a broad spectrum of applications. Stereo height measurements, because of their higher horizontal resolution and dependence on only straightforward geometric relationships, represent a big improvement over previously used infrared-based techniques. Verification using high altitude mountain lakes indicates that stereo cloud height accuracies of ± 0.1–0.2 km are possible near reference points of known elevation. The smallest cloud features observed by the present operational geosynchronous satellites (GOES), which have spatial and temporal resolution of 1.0 km and 3 min, can be measured with height accuracies of ± 0.5 km. Absolute stereo height accuracy, far from landmarks, is also about ± 0.5 km if accurate navigation solutions are available for both satellites. Computer remapping of digital image pairs allows the display and height measurement on time sequences of stereo images using an interactive information processing system. Rapid time sequencing of the series of stereo image pairs gives an effective 4-dimensional representation of cloud dynamics. Several interactive techniques have been developed for point measurements of cloud height and cloud height contouring. The stereo observations have been applied to meteorological problems, including: cloud top height contours of intense convective clouds in hurricanes and severe thunderstorms; cloud top and cloud base height estimates for satellite cloud-wind altitude assignment; atmospheric temperature profiles from the combination of stereo heights and infrared cloud top temperatures; determination of cloud emissivity; and finally, comparisons are made between stereo-observed, tropopause-penetrating thunderstorm tops with altitudes up to 17 km and severe weather observations from radar and surface reports. Present stereo coverage using the operational GOES satellites for research demonstrations includes large areas of North and South America and the surrounding oceans. Recommendations are given for operational stereo observations with greater coverage and improved performance employing a third GOES satellite at 105°W.