On image gradients in digital image correlation

In digital image correlation (DIC), the unknown displacement field is typically identified by minimizing the linearized form of the brightness conservation equation, while the minimization scheme also involves a linearization, yielding a two‐step linearization with four implicit assumptions. These assumptions become apparent by minimizing the non‐linear brightness conservation equation in a consistent mathematical setting, yielding a one‐step linearization allowing a thorough study of the DIC tangent operator. Through this analysis, eight different image gradient operators are defined, and the impact of these alternative image gradients on the accuracy, efficiency, and initial guess robustness is discussed on the basis of a number of academic examples and representative test cases. The main conclusion is that for most cases, the image gradient most common in literature is recommended, except for cases with: (1) large rotations; (2) initial guess instabilities; and (3) costly iterations due to other reasons (e.g., integrated DIC), where a large deformation corrected mixed gradient is recommended instead. Copyright © 2015 John Wiley & Sons, Ltd.     

Gauss curvature-driven image inpainting for image reconstruction

In this paper, we propose a third-order Gauss curvature-driven geometric diffusion Partial Differential Equation for inpainting and reconstructing images. In Gauss curvature-driven diffusion processes, the rate of diffusion is directly proportional to the Gauss curvature value of the level curve. Since the Gauss curvature is the product of principal curvatures, its value become zero when even one of the principal curvatures is zero. Therefore, when Gauss curvature is used as a driving function for diffusion, the evolution preserves some of the meaningful structures with nonzero mean curvature values (viz. curvy edges, corners, etc.). However, the noise features always have nonzero Gauss curvature value and hence the diffusion process effectively removes them. The inpainting property of geometric PDE based on the Gauss curvature is being used in this work for reconstructing lost or degraded information. A filter is proposed to reconstruct the original images from the observed blurred and noisy images along with inpainting the desired image domain.     

彩色图像多尺度引导的深度图像超分辨率重建

为获得更优的深度图像超分辨率重建结果,本文构建了彩色图像多尺度引导深度图像超分辨率重建卷积神经网络。该网络使用多尺度融合方法实现高分辨率(HR)彩色图像特征对低分辨率(LR)深度图像特征的引导,有益于恢复图像细节信息。在对LR深度图像提取特征的过程中,构建了多感受野残差块(MRFRB)提取并融合不同感受野下的特征,然后将每一个MRFRB输出的特征连接、融合,得到全局融合特征。最后,通过亚像素卷积层和全局融合特征,得到HR深度图像。实验结果表明,该算法得到的超分辨率图像缓解了边缘失真和伪影问题,有较好的视觉效果。     

Fast image scanning method in liquid-AFM without image distortion

High speed imaging by atomic force microscopy (AFM) allows one to directly observe the dynamic behavior of a sample surface immersed in liquid media; thus, it has been considered to be an indispensable tool for nanobiotechnology and is used in many research fields, including molecular biology and surface science. For real-time observation of a certain behavior, the high speed imaging technique should be accompanied with a high resolution imaging technique to identify target materials. To improve the image quality at a high scanning rate, we developed a variable-controlled fast scanning method, which originated from the modified squeeze-drag superposition model in liquid media. A collection of non-distorted images was accomplished after proper modification of the operating conditions in a viscous fluid, via the simple handling of loading force and cantilever length. Consequently, a speeded-up AFM imaging process was achieved in the liquid environment at up to 200?μm?s(-1), without attachment of additional devices. The reliability of the proposed method was verified by the characterization of a grating sample immersed in three types of liquid media. In addition, the results were visualized for elastic biomolecules submerged in a liquid with high kinematic viscosity.     

Two-scale image decomposition based image fusion using structure tensor

The PET/SPECT image generates functional information of the human brain. In the field of multimodal medical image fusion, the decomposition scheme of PET/SPECT image in pseudo-color is thought to be negligible. In this article, a two-step model for PET/SPECT image decomposition is proposed to achieve contrast enhancement that inherently captures gradient to distinguish individual edge information from detail information. First, sharp structure is preserved using structure tensor on the intensity component of PET/SPECT image. Second, sharp structure in gray is transformed back into the image in pseudo-color by generalized intensity-hue-saturation, one of the color space methods. The combination of structure tensor and generalized intensity-hue-saturation based fusion technique can preserve not only more intensity information but also functional information content. Finally, we demonstrate the effectiveness of our proposed decomposition method in the context of PET/SPECT image and then make a comparison of fusion result by two-scale image fusion method in terms of the full-reference objective metric structural similarity and no-reference objective metric natural image quality evaluator.     

AFM image reconstruction for deformation measurements by digital image correlation

The scanner drift of the atomic force microscope (AFM) is a great disadvantage to the application of digital image correlation to micro/nano-scale deformation measurements. This paper has addressed the image distortion induced by the scanner drifts and developed a method to reconstruct AFM images for the successful use of AFM image correlation. It?presents such a method, that is to generate a corrected image from two correlated AFM images scanned at the angle of 0° and 90° respectively. The proposed method has been validated by the zero-deformation test. A buckling test of a thin plate under AFM has also been demonstrated. The in-plane displacement field at the centre point of the buckling plate has been successfully characterized by the application of the image correlation technique on reconstructed AFM images.     

机载摄像设备图像稳定方法探讨

通过对现有几种运动估计算法性能进行比较,结合机载红外摄像系统获取动态图像序列的特点,提出了有效地用于机载摄像系统电子稳像的运动估计算法。它具有精度高和速度快等特点,用该算法对实拍的航摄图像序列进行稳像试验,运动矢量的估计时间仅为10ms。实验证明了该算法用于航摄动态图像序列稳定的有效性。     

Low-complexity low-memory energy-efficient image coding for wireless image sensor networks

Wireless image sensor networks are capable of sensing, processing and transmitting the image in hard-to-access regions without expensive network infrastructure and will have great contribution in Internet of Things. These networks are resource constraint systems with limited memory, energy, processing speed and bandwidth. Low computational energy and communication energy will improve the lifetime of these resource-limited networks. In this paper, an energy-efficient low-memory and low-bitrate image coding is designed exclusively for low-power camera-equipped sensor node. The performance of the proposed image coder is analysed in terms of bitrate, image quality, memory size and energy consumption. Experiments are carried out with Atmel ATmega128 processor. The experimental results show that this system consumes only 0.23% of energy consumed by true Discrete Cosine Transform-based Joint Photographic Experts Group (JPEG) standard and offers reasonable image quality suitable for visual perception at low bitrate. This system requires only 19% of memory required by standard JPEG.     

Automated image mosaicking

Abstract

This paper developed and implemented automated image mosaicking procedures to produce seamless and smooth mosaics from random sequences of digital aerial images and satellite images. The procedure employs automated algorithms for global image registration, seam line extraction, radiometric adjustment, and composition of overlap images. Results of the experimentation on mosaicking black and white orthorectified aerial images and on mosaicking multi‐resolution color infrared SPOT‐2 and Landsat‐5 satellite images show that the implementation of automated conjugate point extraction and image matching algorithms automates the establishment of geometric registration among overlapped images, while the seam line selection and two‐step lookup table histogram matching approaches facilitate creating globally smooth and qualitative mosaics. The system developed in this paper makes complex composition of multi‐source multi‐resolution multi‐band images with different geometric and radiometric characteristics an easy and efficient solution for producing reliable mosaic images.     

The composite image

Abstract

Some studies of art have the power to take the reader down a strange and unfamiliar road from which, on looking back, the whole history of art is seen from a new and revealing point of view. Others are merely useful compilations of information about a particular subject which are good to have if no other studies exist, but otherwise not note~orthy. An example of the former is William M. Ivins, Jr's, Prints and Visual Communication. An example of the latter is, I regret to say, Dawn Ades' Photomontage.     

The German image

Abstract

This important book is not a technical history, nor is it ‘sociological’ in any scientific sense; its main thrust is rather in the realm of ‘the history of ideas’ and ‘the history of taste’, and it is thus intimately concerned with human values and attitudes. In this way, and because human nature transceinds national boundaries with conspicuous ease, Fritz Kempe's work is not ‘merely’ about Germany, but about photography and people in general. Without constraining system and without claims to exhaustive coverage, the book manages to get at the spirit and core of relationships by discussing 24 topics, which range from local history (‘Bremen, Wannover, Kassel’) to episodic accounts (‘On the secret magic of the hruman image’). That is its special charm, and also its lasting testament, because photography is really too complex a field to permit a stereotype presentation, if the finer nuances of the human response are to be given their due. If anything is lacking—but it would be chnrlisll to expect a single volume to cover every base—it is a more extensive discussion of the daguerreotype's influence on German painters.     

Waveguide image slicer

A new image slicer with a simple structure has been developed for use in grating spectrometers. The image slicer has polished thin glass plates that work as optical waveguides. It has a square 0.5 mm x 0.5 mm input surface and a steplike output surface with a width of 50 mum that is thin enough for high spectral resolution measurement. The output surface is in the same plane as the input surface so that optical path differences between the plates do not affect the spectrometer optics. The image slicer is efficient, with optical systems with F ratios faster than 10, and can be used at wavelengths that range from visual (lambda = 0.4 mum) to the near infrared (lambda = 2 mum).     

灰度值频数和遍历八方向的指纹图像分割算法

提出基于灰度值频数和遍历八方向的指纹图像分割算法。对于脊谷线灰度值相差较大的,利用灰度直方图上出现频数较多的两个灰度级的差值大小,判断是否为指纹前景区;脊谷线灰度值相差不大的,利用纹线的方向性,通过八个方向的模板计算在各个方向上灰度差值的大小,确定是否为指纹前景区。该方法的阈值可以根据图像自然决定,避免了人为选择阈值的困难和不准确性。对脊谷线灰度值相差较大、不大、较小的指纹图均能容易而准确地分割,只求出指纹的边界而不改变指纹图。实验表明,与常见的分割方法—方向图、方差法相比,该方法的平均误分概率大大减小,比方差法降低5.7875%,比方向图法降低5.6625%,且对指纹图像脊谷线的对比度和方向性要求不高,鲁棒性更强。