An ADC histogram test based on small-amplitude waves

This paper deals with a new method improving the static test for analogue-to-digital converters. The method is based on a histogram procedure using as test signals small-amplitude triangular waves superimposed on suitable constant offset values. The histogram is built over the converter fullscale by varying the offset step by step systematically. A small amplitude and a reduced time slope in comparison to the converter range and slew rate, respectively, lead to static test conditions. This procedure allows inexpensive function generators to be used and the test duration to be dramatically reduced. Experimental results of tests aimed at validating, characterizing, and comparing the proposed method on two different converter architectures are presented.     

Error in the estimation of transition voltages with the standard histogram test of ADCs

In this paper we address the use of overdrive in the standard histogram test of analog to digital converters. The error in the estimation of the transition voltages due to the presence of additive noise is calculated and expressions for the minimum amount of overdrive required are presented. A comparison with previously published work is carried out.     

低汞触媒试用总结

本文总结了在电石法PVC生产工艺中使用的氯化汞含量为4.0%-6.5%的低汞触媒试用情况,并提出了适合低汞触媒使用的触媒初期培养、原料气配比、反应温度等操作控制条件。     

An improved reversible data hiding-based approach for intra-frame error concealment in H.264/AVC

As H.264/AVC video streams are highly compressed, they become sensitive to errors caused by unreliable transmission channels. In order to address this issue, an improved version of Chung et al.’s reversible data hiding-based approach for intra-frame error concealment is proposed for H.264/AVC codec. By using the histogram shifting technique, the original work reversibly embeds the motion vector (MV) of a macroblock (MB) into other MB within the same intra-frame. If an MB is corrupted at the decoder side, the embedded MV can be extracted from the corresponding MB for the recovery of the corrupted MB. However, Chung et al.’s work did not fully exploit the number of coefficients which need to be modified in order to reversibly hiding data, and did not consider many extra nonzero residual blocks produced by data hiding. These two issues could reduce the visual quality of the stego-video. This paper adopts MV data pre-processing, the selection of most suitable embedding region, and the minimum possible amount of histogram modification, which lead to higher PSNR of the stego-video for a given payload. Experimental results further reveal that the proposed method offers stego-video with better visual quality over Chung et al.’s work.     

An efficient reversible data hiding scheme using prediction and optimal side information selection

In this paper, we present an efficient histogram shifting (HS) based reversible data hiding scheme for copyright protection of multimedia. Firstly, an improved HS based multi-layer embedding process for rhombus prediction is employed by introducing a control parameter to explore the correlation of prediction errors. A rate-distortion model for HS embedding is then developed for optimal side information selection, which is especially suitable for low payload reversible data hiding when only a single layer embedding is required. Finally, a modified location map is constructed to facilitate the compression of location map and further increase the embedding capacity. Compared with similar schemes, experimental results demonstrate the superior performance of the proposed scheme in the terms of embedding capacity and stego-image quality.     

A fast and efficient color image enhancement method based on fuzzy-logic and histogram

A new fuzzy logic and histogram based algorithm for enhancing low contrast color images has been proposed here. The method is computationally fast compared to conventional and other advanced enhancement techniques. It is based on two important parameters M and K, where M is the average intensity value of the image, calculated from the histogram and K is the contrast intensification parameter. The given RGB image is converted into HSV color space to preserve the chromatic information contained in the original image. To enhance the image, only the V component is stretched under the control of the parameters M and K. The proposed method has been compared with conventional contrast enhancement techniques as well as with advanced algorithms. All the above techniques were based on the principle of transforming the skewed histogram of the original image into a uniform histogram. The performance of the different contrast enhancement algorithms are evaluated based on the visual quality, Tenengrad, CII and the computational time. The inter comparison of different techniques was carried out on different low contrast color images. Based on the performance analysis, we advocate that our proposed Fuzzy Logic method is well suited for contrast enhancement of low contrast color images.     

基于直方图分析的航空摄像机自动调光方法研究

航空摄像机在空中对地面进行拍摄,拍摄场景复杂,传统的灰度平均值法在一些如有干扰点或背景与目标灰度差别大的场景下曝光会不正确,丢失图像信息,为了解决这些问题,该文在根据图像灰度信息的调光算法以及硬件实现方面进行了相关研究。首先根据当前帧图像的灰度直方图中灰度级为0和255附近的信息进行初调;然后根据图像直方图及其卷积和,搜索其中的峰值区域并确定图像的不感兴趣区域(包含的灰度级单一,信息量少的区域);接着根据这些区域占整幅图像的比重,由权值分配曲线为其分配不同的权值;最后计算加权后的灰度平均值,并将其作为反馈量控制下一帧的调光。实验结果表明,在普通场景下能够准确曝光,在暗背景和亮背景场景下,相比传统方法使图像感兴趣区域信息熵提高10%以上。此方法能适用于多种场景,满足航空摄像机对复杂场景自动调光的需求。     

一种新的直方图核函数及在图像分类中的应用

基于核方法的支持向量机(SVM)以其良好的推广性在图像分类等领域已经得到广泛应用,运用支持向量机的关键是设计有效的核函数。为克服传统核函数较少融合先验知识的弱点,该文提出基于数据驱动的核函数构建方法;并结合词包(BOW)模型,设计了一种基于TF-IDF规则的加权二次卡方(Weighted Quadritic Chisquared, WQC)距离的直方图核函数;在计算直方图之间距离时充分考虑到不同量化区间的不同区分性能,从而增强核函数对不同类别的区分能力。在Caltech101/256等多个经典图像数据集上的分类实验结果验证了该文方法的有效性。     

一种基于颜色块直方图的图像检索方法

提出了一种基于颜色直方图与颜色块相结合的图像检索的新方法。定义了一种新的四维图像特征矢量,它是由颜色直方图,同一种颜色的颜色块个数,同一种颜色块之间的平均距离和同一种颜色块内的平均距离组成。颜色直方图用来获取图像颜色分布的全局信息,利用后三个特征值来获取图像颜色的空间分布信息。通过对图像数据库的检索表明该算法明显优于直方图法。