基于H.26L关键算法模块软件编码器的设计与实现

继制定了H.261、H.263、H.263+等视频压缩标准后,ITU—T正在制定新的视频压缩标准H.26L,目的是为了取得更加有效的图像压缩效果和提供理想的传输接口。文章首先分析了H.26L的各个关键算法模块的原理,与H.263、H.263+进行比较分析,得出其优点;然后阐述如何用VisualC++6.0实现这些算法模块;最后通过实验证明,该文设计的软件编码器能达到更高效的压缩比、信噪比和编码速度,具有一定的实用价值。     

Connectivity-based multiple-circle fitting

This paper proposes a connectivity-based method for circle fitting. The use of pixel connectivity effectively avoids false circle detection, improves the robustness against noise and significantly reduces the computational load. The desired circular models are extracted by searching for meaningful circular arcs. The algorithm does not require a good initial guess, and is effective for extracting an a priori unknown number of circles even when the number of outliers exceeds 50%. The experimental results demonstrate that the proposed method performs well in detecting multiple intersecting or occluded circles.     

Systematic corrections of AVHRR image composites for temporal studies

For quantitative studies of vegetation dynamics, satellite data need to be corrected for spurious effects. In this study, we have applied several changes to an earlier advanced very high resolution radiometer (AVHRR) processing methodology (ABC3; [Remote Sens. Environ. 60 (1997) 35; J. Geophys. Res.-Atmos. 102 (1997) 29625; Can. J. Remote Sens. 23 (1997) 163]), to better represent the various physical processes causing contamination of the AVHRR measurements. These included published recent estimates of the NOAA-11 and NOAA-14 AVHRR calibration trajectories for channels 1 and 2; the best available estimates for the water vapour, aerosol and ozone amounts at the time of AVHRR data acquisition; an improved bidirectional reflectance algorithm that also takes into consideration surface topography; and an improved image screening algorithm for contaminated pixels. Unlike the previous study that compared the composite images to a single-date AVHRR image, we employed coincident TM images to approximate the AVHRR pixel field of view during the data acquisition. Compared to ABC3, the modified procedure ABC3V2 was found to improve the accuracy of AVHRR pixel reflectance estimates, both in the sensitivity (slope) of the regression and in r². The improvements were especially significant in AVHRR channel 1. In comparison with reference values derived from two full TM scenes, the corrected AVHRR surface reflectance estimates had average standard errors values of ±0.009 for AVHRR C1, ±0.019 for C2, and ±0.04 for NDVI; the corresponding r² values were 0.55, 0.80, and 0.50, respectively. The changes in ABC3V2 were not able to completely remove interannual variability for land cover types with little or no vegetation cover, which would be expected to remain stable over time, and they increased the interannual variability of mixed forest and grassland. These results are attributed to a combination of increased sensitivity to interannual dynamics on one hand, and the inability to remove all sources of noise for barren or sparsely vegetated northern land cover types on the other.     

Agriculture satellite image segmentation using a modified artificial Hopfield neural network

Beekeeping plays an important role in increasing and diversifying the incomes of many rural communities in Kingdom of Saudi Arabia. However, despite the region’s relatively good rainfall, which results in better forage conditions, bees and beekeepers are greatly affected by seasonal shortages of bee forage. Because of these shortages, beekeepers must continually move their colonies in search of better forage. The aim of this paper is to determine the actual bee forage areas with specific characteristics like population density, ecological distribution, flowering phenology based on color satellite image segmentation. Satellite images are currently used as an efficient tool for agricultural management and monitoring. It is also one of the most difficult image segmentation problems due to factors like environmental conditions, poor resolution and poor illumination. Pixel clustering is a popular way of determining the homogeneous image regions, corresponding to the different land cover types, based on their spectral properties. In this paper Hopfield neural network (HNN) is introduced as Pixel clustering based segmentation method for agriculture satellite images.     

Separable reversible data hiding in encrypted image based on pixel value ordering and additive homomorphism

This work proposes a separable reversible data hiding scheme in encrypted images based on pixel value ordering (PVO). After the original image is encrypted using homomorphism encryption by the content owner, the data hider embeds the secret data in encrypted domain. The PVO strategy realizes hiding data in each block. Additive homomorphism guarantees the performance of PVO in encrypted domain is close to that in plain domain. Besides, the homomorphism encryption does not cause data expansion, and the payload can be further improved. With the watermarked encrypted image, if the receiver has only the data hiding key, he can extract the additional data. If the receiver has only the encryption key, he can obtain a decrypted image similar to the original one. If the receiver has both the data hiding key and the encryption key, he can extract the additional data without any error and recover the original image losslessly.     

基于OpenGL的SetPixel函数的两种实现方法及对比分析

OpenGL提供了数百个功能丰富的图形库函数,但并没有直接给出单个像素的读写函数。该文讨论了基于OpenGL的写像素函数SetPixel的两种实现方法,用程序实例对它们进行了对比分析,指出了它们存在的重要差异和缺陷。     

用CCD光电测量方法跟踪焊接筒体环形坡口的数控系统

主要介绍了一种在焊接领域里用CCD光电测量的方法进行自动跟踪焊接的数控系统,在实践中对硬件的设计和坡口的图像软件分析方面作了相应的总结。     

基于不变特征的标志识别技术研究

标志识别是近距离空间交会对接中的一项重要的关键技术.在空间交会对接过程中,太阳和月球等各种天体以及飞行器上零部件的辐射与反射都会影响CCD的成像,形成大量杂散光干扰.为此,本文首先设计了具有不变特征的标志系统,然后根据标志系统固有的不变特征,详细设计了左右像点匹配、远场像平面不变特征识别、近场像平面预测识别以及像空间模型匹配全等识别等一套完整算法,可以保证彻底消除杂散光的干扰,正确可靠地完成各个标志灯像点的辨识.模拟图像仿真实验和真实图像仿真实验结果验证了算法的正确性和可靠性.     

基于忆阻细胞自动机的图像像素值置换加密技术

忆阻细胞自动机是一种全新的细胞自动机,它的响应会引起细胞状态和细胞间链接状态的变化.在分析了忆阻细胞自动机中的细胞间链接状态丰富变化的基础上,设计了一种全新的图像加密算法:以一个w×H的忆阻自动机阵列为公钥,以细胞的初始状态和细胞迭代次数为私钥,将细胞与相邻细胞间的一组链接状态加权后设置成加密矩阵,同时采用像素置换方法对数字图像进行加密.这种加密算法具有较好的混乱特性、扩散特性和良好的保密性、抗蛮力破解特性,能够满足数字图像加密的安全性要求.