Learning Probabilistic Transfer Functions: A Comparative Study of Classifiers

Complex volume rendering tasks require high‐dimensional transfer functions, which are notoriously difficult to design. One solution to this is to learn transfer functions from scribbles that the user places in the volumetric domain in an intuitive and natural manner. In this paper, we explicitly model and visualize the uncertainty in the resulting classification. To this end, we extend a previous intelligent system approach to volume rendering, and we systematically compare five supervised classification techniques – Gaussian Naive Bayes, k Nearest Neighbor, Support Vector Machines, Neural Networks, and Random Forests – with respect to probabilistic classification, support for multiple materials, interactive performance, robustness to unreliable input, and easy parameter tuning, which we identify as key requirements for the successful use in this application. Based on theoretical considerations, as well as quantitative and visual results on volume datasets from different sources and modalities, we conclude that, while no single classifier can be expected to outperform all others under all circumstances, random forests are a useful off‐the‐shelf technique that provides fast, easy, robust and accurate results in many scenarios.     

A Locally Adaptive Multimode Photodetector Circuit

Photodetection circuits form the first stage of the artificial image acquisition process. The image acquisition circuits discussed in this paper pertain to circuits fabricated in a standard CMOS process. Such circuits offers advantages such as random access to a pixel, faster readout, integration of processing circuitry on the same die, low voltage and low power dissipation, and lower cost over the conventional Charge Coupled Device (CCD) process. We describe a new locally adaptive multimode photodetector circuit. The advantages of the circuit are local adaptation, wide dynamic range, excellent sensitivity, and large output voltage swing. The circuit was fabricated in the 2 CMOS process through MOSIS. Simulation and experimental results of the circuit are given.     

基于像素累积积分的红外读出电路研究

像素累积积分(PA)与时间延迟积分( TDI)是应用较多的红外读出电路积分技术.TDI应用于扫描型焦平面,PA应用于凝视型焦平面.介绍了TDI的原理和作用,分析了PA的原理和电路实现.通过理论分析和仿真显示PA可以增强读出电路的信噪比和电荷存储容量.     

Image analysis system for quantitative metallography

This paper describes a Z-80 microprocessor-based image analyzer developed for global parameter evaluation of images over a 256 × 256 pixel frame. It consists of a microscope,ccd scanner, 6-bit videoadc, Z-80 computer and an image display monitor. Facilities are provided for feature erosion/dilation and halo correction. The paper also presents the details of another more powerful user microprogrammable HP1000 minicomputer-based image analysis system under development. This system consists of an optical microscope/epidiascope coupled to a chalnicon scanner. Here the 512 × 512 pixel image is acquired with 8-bit resolution. It provides for shading correction, auto-delineation, image processing and image analysis functions for evaluation of various basic and derived parameters. Both the systems are software intensive and are realised according to requirements of quantitative metallography. They can also be used for analysis of images obtained in the fields of biology, medicine, geological survey, photography and space.     

基于多帧"差分"图像的分辨率提高算法

介绍了一种基于多帧"差分"图像重建高分辨率图像技术,并从CCD数字化采样能量的角度分析了多幅低分辨率的"差分"图像与高分辨率图像各像素灰度值的对应关系,给出了通过图像"差分"技术提高探测图像分辨率的倍数与所需CCD最少数目之间的一般规律.最后,采用Matlab软件以一幅黑白条纹均匀分布的图像作为目标物,模拟了图像"差分"技术的实现过程,仿真结果表明了该技术的可行性.     

长庆油田油气泄漏防治体系建设与应用

简单阐述Pixel Factory体系结构及其特点,结合航空、航天遥感影像数据处理项目重点分析该系统在海量遥感影像数据处理中所展现出的优势并针对存在的相关问题进行探讨。实践证明,该系统在传统正射影像制作、海量卫星影像数据处理方面具有明显算法优势,但DSM自动计算算法及框幅式航摄数据空中三角测量功能仍需增强。     

A Comprehensive Survey on Sampling‐Based Image Matting

Sampling‐based image matting is currently playing a significant role and showing great further development potentials in image matting. However, the consequent survey articles and detailed classifications are still rare in the field of corresponding research. Furthermore, besides sampling strategies, most of the sampling‐based matting algorithms apply additional operations which actually conceal their real sampling performances. To inspire further improvements and new work, this paper makes a comprehensive survey on sampling‐based matting in the following five aspects: (i) Only the sampling step is initially preserved in the matting process to generate the final alpha results and make comparisons. (ii) Four basic categories including eight detailed classes for sampling‐based matting are presented, which are combined to generate the common sampling‐based matting algorithms. (iii) Each category including two classes is analysed and experimented independently on their advantages and disadvantages. (iv) Additional operations, including sampling weight, settling manner, complement and pre‐ and post‐processing, are sequentially analysed and added into sampling. Besides, the result and effect of each operation are also presented. (v) A pure sampling comparison framework is strongly recommended in future work.     

High-capacity reversible data hiding in encrypted image based on specific encryption process

This paper proposes a novel reversible data hiding method in encrypted images based on specific encryption process. In the proposed specific encryption algorithm, the stream cipher and prediction error are combined to vacate room for data embedding. After that, a permutation operation is performed on the encrypted image to improve the security. In the embedding process, we can embed a large amount of secret data in the encrypted image by pixel value expansion because most of the pixel values are less than 128 by the specific encryption process. At the receiver end, the encrypted image can be recovered from the marked encrypted image without knowing the secret data. Therefore, even if the recipient only has the encryption key, the original image will be perfectly recovered. If the recipient only has the data-hiding key, the secret data will be extracted. And if the recipient has both keys, the original image and the secret data are both available. The proposed method achieves a higher embedding capacity than that of methods based on vacating room after encryption. It does not require the image owner to perform reversible data hiding techniques on the original image, which is more convenient than methods based on reserving room before encryption. Experimental results demonstrate that the proposed method outperforms other state-of-the-art methods.     

Specular highlight region restoration using image clustering and inpainting

A novel specular highlight restoration algorithm has been proposed to remove the specular highlight in a real-time vision system. In this paper, the specular highlight region has been detected and it has been restored by image inpainting method. Most of specular highlight detection algorithms are effective only for a single image. And the auto-threshold algorithm has been implemented in real time, but, it has still low reliability with a heavy computational cost. The proposed system detects pixels corresponding to the specular highlight region in the HSI color space through a newly defined classification table. So, Specular highlight can be detected quickly with these simplified classification table. In addition, it has versatility because it can be combined with various existing high-performance image inpainting method. The superiority of the proposed algorithm is compared with the conventional specular highlight removal algorithm by combining proposed algorithm with two high-performance image inpainting techniques.