Changes In Image Size Research Articles

Perceptual Thresholds for Radial Optic Flow Distortion in Near-Eye Stereoscopic Displays.

We provide the first perceptual quantification of user's sensitivity to radial optic flow artifacts and demonstrate a promising approach for masking this optic flow artifact via blink suppression. Near-eye HMOs allow users to feel immersed in virtual environments by providing visual cues, like motion parallax and stereoscopy, that mimic how we view the physical world. However, these systems exhibit a variety of perceptual artifacts that can limit their usability and the user's sense of presence in VR. One well-known artifact is the vergence-accommodation conflict (VAC). Varifocal displays can mitigate VAC, but bring with them other artifacts such as a change in virtual image size (radial optic flow) when the focal plane changes. We conducted a set of psychophysical studies to measure users' ability to perceive this radial flow artifact before, during, and after self-initiated blinks. Our results showed that visual sensitivity was reduced by a factor of 10 at the start and for ~70 ms after a blink was detected. Pre- and post-blink sensitivity was, on average, ~O.15% image size change during normal viewing and increased to ~1.5- 2.0% during blinks. Our results imply that a rapid (under 70 ms) radial optic flow distortion can go unnoticed during a blink. Furthermore, our results provide empirical data that can be used to inform engineering requirements for both hardware design and software-based graphical correction algorithms for future varifocal near-eye displays. Our project website is available at https://gamma.umd.edu/ROF/.

The Effect of Image Size on the Deep Learning Approach for Classifying Covid-19 Pneumonia

The scope of this study is related to the classification of covid-19 pneumonia which uses X-ray images of the lungs as input and is then classified into 3 categories, namely normal (healthy), pneumonia, and covid-19 pneumonia. The classification process uses a deep learning approach, which is becoming a trend nowadays because its performance is better than conventional machine learning approaches. The image dataset in this study is a collection of X-ray images of the lungs consisting of 1,525 normal images, 1,525 pneumonia images, and 1,525 Covid-19 pneumonia images. These images vary in size, but all images are larger than 1000x1000 pixels. The large size of the image makes the training time long and the computational resources required are large. Deep learning machines need to reduce the size of the image to make the process more effective. However, changes in image size may affect classification performance. Therefore, we conducted experiments in this study to determine the effect of image size changes on the classification performance of COVID-19 pneumonia using a deep learning approach. We use the Convolutional Neural Network method, which uses 22 layers with 5 convolution layers, for classification. The experimental results show that the size of the input image affects the classification performance of covid-19 pneumonia. This study provides important information that larger image sizes do not always result in better classification performance. In addition, the image size that is too small causes very low classification performance. The performance of the classification of covid-19 pneumonia using the CNN method shows the most optimal results at an input image size of 500x500 pixels.

Hybrid multistage framework for data manipulation by combining cryptography and steganography

In today's rapidly growing communication and internet technologies, such as 5G, cloud computing, and blockchain, information security has become a critical component. When data is transmitted in its raw form, it is vulnerable to a variety of cybersecurity assaults. In this hybrid multi-stage data encryption architecture, which builds sequential and pseudo-random encoding/decoding algorithms with pre-stage text encryption discovered that image resolution and attributes were unaffected by the change in image size after testing several text sizes with the cover image and various image formats, it is suitable that the text size should be 15% smaller than the cover image. Furthermore, when compared to sequential encoding/decoding, the hybrid cryptography and steganography-pseudo-random encoding/decoding procedure is more efficient and time consuming.

Aniseikonia and visual functions with optical correction and after refractive surgery in axial anisometropia.

To evaluate differences in the subjective aniseikonia and stereoacuity in patients with axial anisometropia after full correction of the refractive error with spectacles, contact lenses, and refractive surgery. A prospective study was performed in Cairo University Hospitals on 20 patients with axial anisometropia caused by unilateral myopia > 5 D with > 4 D inter-ocular difference in spherical equivalent who were suitable candidates for excimer laser ablation (LASIK) or implantable collamer lens implantation (ICL). All patients had measurement of best-corrected visual acuity (BCVA), fusion, stereoacuity, and magnitude of aniseikonia with spectacles, contact lenses, and after surgery. The mean age at time of surgery was 25.7 ± 3.1years. There were no statistically significant differences in the BCVA or stereoacuity with spectacles, contact lenses, or after refractive surgery. Microkonia < 5%) was perceived with spectacles in 8 patients (40%) and remained unchanged in 7 of these 8 patients with contact lenses. Following LASIK (n = 11), there was an induced macrokonia < 2% in 4 patients (36%), persistent microkonia of 3% in 1 patient (9%), and no change in image size in 6 (55%) patients. Following ICL implantation (n = 9), there was a perceived macrokonia of 2% in 4 patients (44%), disappearance of microkonia in 1 patient (11%) and no change in 4 patients (44%). Differences in BCVA, stereoacuity, and aniseikonia after correction of anisometropia by glasses, contact lens and surgery are both clinically and statistically insignificant. Retinal or neural adaptation might have a role in correction for differences in image size.

Deep learning based solder joint defect detection on industrial printed circuit board X-ray images

With the improvement of electronic circuit production methods, such as reduction of component size and the increase of component density, the risk of defects is increasing in the production line. Many techniques have been incorporated to check for failed solder joints, such as X-ray imaging, optical imaging and thermal imaging, among which X-ray imaging can inspect external and internal defects. However, some advanced algorithms are not accurate enough to meet the requirements of quality control. A lot of manual inspection is required that increases the specialist workload. In addition, automatic X-ray inspection could produce incorrect region of interests that deteriorates the defect detection. The high-dimensionality of X-ray images and changes in image size also pose challenges to detection algorithms. Recently, the latest advances in deep learning provide inspiration for image-based tasks and are competitive with human level. In this work, deep learning is introduced in the inspection for quality control. Four joint defect detection models based on artificial intelligence are proposed and compared. The noisy ROI and the change of image dimension problems are addressed. The effectiveness of the proposed models is verified by experiments on real-world 3D X-ray dataset, which saves the specialist inspection workload greatly.

Deteksi Objek Nomor Kendaraan Pada Citra Kendaraan Bermotor

Motor vehicle police numbers recognation is one of the most important topics in the processof building a smart transportation system. Also this concept and introduction system will bevery useful in various combinations of applications, including in monitoring vehicles when acrime occurs. In this research an object recognition model will be developed by reviewing thesize of the object vertically. Image processing stages starting from the stages of image sizechange, image grayscale, edge detection, morphological operations to the segmentation stage.Based on tests conducted, it was found that the implemented model can be used in the processof recognizing vehicle numbers in the image of motorized vehicles

Does spectacle use lead to vestibular suppression?

Laboratory experiments indicate that changes in retinal image size result in adaptive recalibration or suppression of the vestibulo-ocular reflex. Myopia correction with spectacles or contact lenses also leads to retinal image size changes, and may bring about similar vestibulo-ocular reflex alterations. A hypothesis-generating preliminary investigation was conducted. In this cross-sectional study, findings of electronystagmography including bithermal caloric testing were compared between 17 volunteer myopes using spectacles or contact lenses and 17 volunteer emmetropes (with no refractive error). Bilateral hypoactive caloric responses were demonstrated in 6 of 11 spectacle users, in 1 of 6 contact lens users and in 1 of 17 emmetropes. Hypoactive caloric responses were significantly more likely in spectacle users than in emmetropes (p < 0.01; relative risk = 9.3). A significant proportion of myopes using spectacles have vestibulo-ocular reflex suppression, as demonstrated by the caloric test. This has implications for the interpretation of electronystagmography and videonystagmography results, and highlights spectacle use as a possible cause of vestibular impairment. Further corroboration of these findings is warranted, with more precise and direct vestibulo-ocular reflex tests such as rotational tests and the head impulse test.

영상 이미지 색채 감성트리를 통한 대표감성크기 변화 연구

영상 이미지 색채 감성트리를 통한 대표감성크기 변화 연구

Measurement of spherical and cylindrical power in ophthalmic lenses based in the change of lateral amplification.

In this article, we present a new technique to measure spherical and cylindrical power in ophthalmic lenses. This method is based in the change of lateral amplification produced by an optical system when introducing an ophthalmic lens. Ophthalmic lens power is calculated by considering the change in image size from a reference object and its own image seen through the ophthalmic lens. Mathematical analysis is presented along with the experimental setup and the obtained results. Several algorithms were applied to the obtained results as a method to compensate the error in order to fit into ISO 8598 specifications.

3차원 점군데이터의 깊이 영상 변환 방법 및 하드웨어 구현

In the motion recognition system using depth image, the depth image is converted to the real world formed 3D point cloud data for efficient algorithm apply. And then, output depth image is converted by the projective world after algorithm apply. However, when coordinate conversion, rounding error and data loss by applied algorithm are occurred. In this paper, when convert 3D point cloud data to depth image, we proposed efficient conversion method and its hardware implementation without rounding error and data loss according image size change. The proposed system make progress using the OpenCV and the window program, and we test a system using the Kinect in real time. In addition, designed using Verilog-HDL and verified through the Zynq-7000 FPGA Board of Xilinx.

Interactions between cues to visual motion in depth

Information about the motion in depth of an object along the midline of a stationary observer is provided by changes in image size (looming), changes in vergence produced by changes in binocular disparity of the images of the object, and changes in relative disparity between the moving object and a stationary object. Each of these cues was independently varied in the dichoptiscope, which is described in Howard, Fukuda, and Allison (2013). The stimuli were a small central dot and a textured surface moving to and fro in depth along the midline. Observers tracked the motion with the unseen hand. Image looming was normal or absent. The change in vergence was absent, normal, more than normal, or reversed relative to normal. Changing relative disparity between the moving stimulus and a stationary surface was present or absent. Changing vergence alone produced no motion in depth for the textured surface but it produced some motion of the dot. Looming alone produced strong motion in depth for the texture but not for the dot. When the direction of motion indicated by looming was opposite that indicated by changing relative disparity observers could use either cue. The cues dissociated rather than combined.

A Robust Scalable Spatial Spread-Spectrum Video Watermarking Scheme Based on a Fast Downsampling Method

This paper presents a robust spatial spread- spectrum (SS) video watermarking scheme with adaptive detection for H.264/AVC and SVC. We introduce a fast image size change method in DCT domain to obtain a low- pass and downsized version of the video frame for embedding, which protects the watermarking signal from being damaged by downsampling during SVC encoding. And then we embed watermark bits by SS method with exploiting the Just Noticeable Distortion (JND) model to dynamically adjust the embedding strength. The watermark will be spread to the original video after the upsampling of the embedded downsized version. Furthermore, we deduce a detection model based on a likelihood ratio test to realize adaptive detection and design a different detection strategy for the base layer of SVC-encoded video. Simulation results prove the validity of the detection model and show that the proposed watermarking algorithm has strong robustness against not only H.264/AVC-encoded I-frames, P-frames and B-frames, but also SVC-encoded I-frames and P-frames while preserving the perceptual quality.

Magnifications of single and dual element accommodative intraocular lenses: paraxial optics analysis

Using an analytical approach of paraxial optics, we evaluated the magnification of a model eye implanted with single-element (1E) and dual-element (2E) translating-optics accommodative intraocular lenses (AIOL) with an objective of understanding key control parameters relevant to their design. Potential clinical implications of the results arising from pseudophakic accommodation were also considered. Lateral and angular magnifications in a pseudophakic model eye were analyzed using the matrix method of paraxial optics. The effects of key control parameters such as direction (forward or backward) and distance (0 to 2 mm) of translation, power combinations of the 2E-AIOL elements (front element power range +20.0 D to +40.0 D), and amplitudes of accommodation (0 to 4 D) were tested. Relative magnification, defined as the ratio of the retinal image size of the accommodated eye to that of unaccommodated phakic (rLM(1)) or pseudophakic (rLM(2)) model eyes, was computed to determine how retinal image size changes with pseudophakic accommodation. Both lateral and angular magnifications increased with increased power of the front element in 2E-AIOL and amplitude of accommodation. For a 2E-AIOL with front element power of +35 D, rLM(1) and rLM(2) increased by 17.0% and 16.3%, respectively, per millimetre of forward translation of the element, compared to the magnification at distance focus (unaccommodated). These changes correspond to a change of 9.4% and 6.5% per dioptre of accommodation, respectively. Angular magnification also increased with pseudophakic accommodation. 1E-AIOLs produced consistently less magnification than 2E-AIOLs. Relative retinal image size decreased at a rate of 0.25% with each dioptre of accommodation in the phakic model eye. The position of the image space nodal point shifted away from the retina (towards the cornea) with both phakic and pseudophakic accommodation. Power of the mobile element, and amount and direction of the translation (or the achieved accommodative amplitude) are important parameters in determining the magnifications of the AIOLs. The results highlight the need for caution in the prescribing of AIOL. Aniso-accommodation or inter-ocular differences in AIOL designs (or relative to the natural lens of the contralateral eye) may introduce dynamic aniseikonia and consequent impaired binocular vision. Nevertheless, some designs, offering greater increases in magnification on accommodation, may provide enhanced near vision depending on patient needs.

On invariance analysis of Zernike moments in the presence of rotation with crop and loose modes

Zernike moments are widely applied in digital image processing fields based on many desirable properties, such as rotational invariance, noise robust and efficient representation of pattern. On the computational analysis of Zernike moment is challenging issue. From an algorithmic aspect, in this paper we investigate the effect of image rotation (including crop rotation and loose rotation) operations on Zernike moments in both theoretical and experimental ways. For the crop rotation, we suggest to extract the Zernike moments by mapping the image over a disc instead of inside a circle since the outside of an image after the crop rotation will be distorted. Referring to the loose rotation, we propose a preprocessing step (which is called image size normalization) to embed an image and its rotated versions into a predefined size of zero-value image in such a way that the effect of image size change due to loose rotation can be eliminated. By incorporating the proposed image size normalization operation, we introduce an effective extraction method of image Zernike moments against loose rotation operation. Experimental results show the validity of the proposed extraction method.

Efficient Schemes for Compressed-Domain Image Resizing

Fast schemes for compressed-domain image size change, are proposed. Fast Winograd DCTs are applied to resizing images by a factor of two to one. First, we speed up the DCT domain downsampling scheme which uses the bilinear interpolation. Then, we speed up other image resizing schemes which use DCT lowpass truncated approximations. The schemes proposed here reduce the computational complexities significantly, while there is no difference in the overall quality of the images compared to previous works.

Optical Magnification Matrix: Near Objects in the Paraxial Case

For appropriate patient management understanding, the problems due to the change of image size in the near magnification matrix of spectacles are important. The purpose here is to derive an equation for the paraxial 2 x 2 magnification matrix of spherocylindrical two-surface optical instruments (spectacles) in front of an eye at a finite object distance. A 2 x 2 stepalong method for the contribution factors to the magnification matrix is developed, starting from a definition within a ray-tracing picture before translating it into quadratic-order wave-tracing concepts. Extensive use is made of the wave-tracing description of propagating wavefronts by 2 x 2 vergence matrices for deriving an expression for the magnification matrix in ophthalmic terms. A 2 x 2 magnification matrix as a function of the dioptric power matrices of the interfaces as well as the object distance is given explicitly. The expression is an intuitive product representation possessing the familiar appearance of a shape factor times a power factor. Additionally, however, the result contains now a scaling prefactor depending on the finite object distance, which would not be present for objects at infinity. The result is a generalization of the formerly known result for the paraxial magnification matrix for infinite object distance. The effect of the finite object distance correction is small but not negligible. Moreover, the methods for deriving this result serve as a starting point for an even more general treatment of oblique incidence in a future work.

P‐43: Effects of Changing Image Size on Depth Perception Using a Floating 3‐D Display

AbstractA floating‐image display produces 3‐D effects using a lens system that makes an image appear to float in the air. The authors examine the effects on depth perception and asthenopia of viewing a floating image that continuously changes in size. The results of the experiments suggest that viewers perceive the floating image to be moving back and forth as the image size changes despite the fact that the image's actual position does not change. Monocular depth cues, especially changes in size, enhanced the 3‐D effects of images presented on the floating‐image display.

Modeling of lateral magnification changes due to changes in corneal shape or refraction

Background and Purpose Especially after corneal surgery the lateral magnification of the eye providing the retinal image size of an object is a crucial factor influencing visual acuity and binocularity. The purpose of this study is to describe a paraxial computing scheme calculating lateral magnification changes (ratio of the image sizes before and after surgery) due to variation in corneal shape and spectacle refraction. Calculation strategy From the 4 × 4 refraction and translation matrices the system matrix representing the entire ‘optical system eye’ and the pupil matrix describing the sub-system from the spectacle correction to the aperture stop were defined for the state before and after surgery. As the chief ray is assumed to pass through the centre of the aperture stop, the 2 × 2 matrix of the lateral magnification ratio from preoperative to postoperative is described by the 2 × 2 sub-matrices of the respective pupil matrices. The cardinal meridians can be extracted by calculating the eigenvalues and eigenvectors. Working example Vertex distance 14 mm, measured distance between corneal apex and aperture stop 3.6 mm, keratometry 39 D + 6 D/0° to 47 D + 3 D/30° and refraction 3.5 D − 5 − 5 D/5° to −4.0 D − 3.5 D/25° preoperatively to postoperatively. The matrix of magnification ratio from preop to postop yields (0.8960 −0.0085;0.0074 0.9371) and the eigenvalues decomposition provided a 10.7% minified image at 170.1° and a minified image of 6.1% at 78.7°, which both are clinically relevant. Conclusion We presented a straight-forward computer-based strategy for calculation of retinal image size changes using 4 × 4 matrix notation. With this model the meridional changes in lateral magnification from the preoperative to the postoperative stage or between follow-up stages can be estimated from keratometry, refraction, vertex distance and anterior chamber depth, which might be important for binocularity and vision tests in corneal surgery.

Changes in image size affect perceived contrast

Changes in image size affect perceived contrast

Two eyes in action

Do relative binocular disparities guide our movements in depth? In order to find out we asked subjects to move a 'cursor' to a target within a simulated horizontal plane at eye height. They did so by moving a computer mouse. We determined how quickly subjects responded to the target jumping in depth. We found that it took subjects about 200 ms to respond to changes in binocular disparity. Subjects responded just as quickly if the cursor was temporarily only visible to one eye near the time that the target jumped in depth, and less vigorously, though just as quickly, if the cursor jumped rather than the target, so the fastest binocular responses cannot be based directly on the relative retinal disparity between the target and the cursor. Subjects reacted faster to changes in the target's height in the visual field than to changes in binocular disparity, but did not react faster to changes in image size. These results suggest that binocular vision mainly improves people's everyday movements by giving them a better sense of the distances of relevant objects, rather than by relative retinal disparities being used to directly guide the movement. We propose that relative disparities only guide parts of very slow movements that require extreme precision.