彩色扫描仪的光谱反射率估计方法

为从扫描仪获取精确的、设备无关的颜色描述,必须对扫描仪进行颜色表征(Characterization)。考虑到实际扫描仪的成像过程往往偏离线性反射模型,并且训练样本在颜色空间中的不同分布对颜色估计的精度有较大影响,提出了一种基于有限样本加权训练的彩色扫描仪光谱表征方法,从而可以从低维的RGB颜色值计算得到精确的光谱反射率。 实验结果表明,该方法在色度及反射率精度方面均明显优于先前的方法。     

基于彩色扫描仪的图像光谱重构

针对彩色扫描仪的特点,采用主元分析法(PCA)和反向传播(BP)人工神经网络(ANN)相结合的方法对图像光谱重构进行研究。选择IT8.7/2标准色卡作为训练样本,将该色卡中的另一组色靶作为检验样本以讨论不同网络结构以及不同主元数和训练样本数对光谱重构的影响,再以自然色系统(NCS)色卡为检验样本来分析不同种类的训练和检验样本与光谱重构性能的关系。实验结果表明,采用3-14-6网络结构和6个主元数是最佳选择,训练样本和扫描目标之间的一致性是基于彩色扫描仪图像光谱重构的关键所在。     

多点分段单步校正法在接触式图像传感器扫描仪上的实现

提出了一种接触式图像传感器(CIS)扫描仪非均匀校正的新方法,能够快速高效地完成对CIS扫描仪彩色图像的非均匀校正,消除了CIS的颜色差异。采用多点分段单步法进行标定,采用现场可编程门阵列实现校正,并最终得到颜色均匀的彩色图像。对于分辨率高达1200dpi的CIS扫描仪,采集一次样板纸完成全部颜色空间的分段标定,图像传输的同时完成校正,校正过程仅耗时0.125μs。实际应用效果显示校正后R,G,B三个通道的像素误差控制在5个像素以内,相比校正前图像均匀性提升10倍左右,比传统两点法提升3倍左右,且明显改善图像颜色突变、暗淡以及随机条纹等问题。     

基于多项式回归模型的扫描仪色度特征化

为了实现扫描仪精确的色度特征化,详细研究了多种不同项数、不同变换类型多项式回归模型,多项式的项数分别为3,5,9,11,18和20,变换类型包括扫描仪RGB空间到CIEXYZ或CIELAB空间的多种变换。以ANSIIT8.7/2标准色卡为色靶,对同一台扫描仪进行了色度特征化。实验结果表明,多项式项数小于11时,不同类型模型间的精度差异大,且线性化RGB能提高模型精度;项数大于11时,模型间精度差异缩小,而线性化RGB反而会降低模型精度。实验中,多项式项数为20时的RGB到CIEXYZ变换模型特征化精度最好,平均色差和最大色差分别为0.832和2.988 CIELAB色差单位。     

一种结合JPEG压缩编码的彩色图像加密算法

为了研究针对联合图像专家小组压缩标准（joint photographic experts group,JPEG）彩色图像特点的加密算法,综合选择加密和在编码过程中加密两种思路,提出了一种空域和频域结合的加密算法. 首先在空域对8×8分块进行扩散置乱,然后利用边缘检测手段找出包含细节信息较多的重要分块,先加密所有分块中的直流（direct current,DC）系数,再选择重要分块中的一部分交流（alternating current,AC）系数进行加密,最后将分块重要性标记信息嵌入AC系数中进行传输. 通过理论分析和大量实验证明,算法格式兼容,密文图像视觉效果好、色彩分布均匀;算法密钥空间大,密钥敏感性强,安全性良好. 关键词： JPEG彩色图像 边缘检测 选择加密 结合编码加密     

海洋水色水温扫描仪精确大气漫射透射比计算

海洋水色水温扫描仪(COCTS)是中国海洋水色系列卫星上的主遥感器,主要用于探测我国及全球部分海域的海洋水色和水温环境信息.大气漫射透射比计算是COCTS大气校正的必需过程,直接影响COCTS大气校正和水色信息反演的精度.提出了基于加倍法解大气-海洋耦合矢量辐射传输方程的大气漫射透射比精确计算方法,通过与SeaWiFS精确大气漫射透射比查找表计算结果的比较,结果表明计算相对误差小于1.5%,而当观测天顶角小于60°时,计算相对误差小于0.5%,可以用来生成COCTS的精确大气漫射透射比查找表.在此基础上,生成了专门针对COCTS的精确大气漫射透射比查找表.     

基于BP神经网络的复杂彩色图像文本定位

针对复杂彩色图像中文本的特征,提出了基于小波变换和BP神经网络甄别文本区域的算法.该算法首先利用文本块的边缘特征遴选出备选图像块,而后采用小波变换提取备选图像块的纹理特征,把这些纹理特征参量连同图像块的颜色特征和笔画特征参量输入训练好的BP神经网络,判断备选图像块是否包含文本.该方法运算简单,定位时间短.采用专用的文本定位比赛用图进行实验的结果表明,定位准确率可达到92%,召回率为87.4%.     

基于BP神经网络的复杂彩色图像文本定位*

针对复杂彩色图像中文本的特征,提出了基于小波变换和BP神经网络甄别文本区域的算法.该算法首先利用文本块的边缘特征遴选出备选图像块,而后采用小波变换提取备选图像块的纹理特征,把这些纹理特征参量连同图像块的颜色特征和笔画特征参量输入训练好的BP神经网络,判断备选图像块是否包含文本.该方法运算简单,定位时间短.采用专用的文本定位比赛用图进行实验的结果表明,定位准确率可达到92％,召回率为87.4%.     

A novel algorithm for automatic localization of human eyes

Based on geometrical facial features and image segmentation, we present a novel algorithm for automatic localization of human eyes in grayscale or color still images with complex background. Firstly, a determination criterion of eye location is established by the prior knowledge of geometrical facial features. Secondly, a range of threshold values that would separate eye blocks from others in a segmented face image (i.e., a binary image) are estimated. Thirdly, with the progressive increase of the threshold by an appropriate step in that range, once two eye blocks appear from the segmented image, they will be detected by the determination criterion of eye location. Finally, the 2D correlation coefficient is used as a symmetry similarity measure to check the factuality of the two detected eyes. To avoid the background interference, skin color segmentation can be applied in order to enhance the accuracy of eye detection. The experimental results demonstrate the high efficiency of the algorithm and correct     

Examination of the developed scanning system for red-green-blue laser projector with a feedback control

The galvanometric scanning system is widely used in laser material processing and laser shows. The scanner is a broadband component, damped sufficiently to operate over a wide range of frequencies, from zero to a higher value related to its mechanical resonance. Developing a galvanometric scanner is an important issue in the design of optical systems. This study focuses on the development of the scanning system for a laser projector using red, green, and blue diode lasers. The performance of the laser projector, which consists of the scanning control system, color control system, and position detector, is also discussed.     

Approximating the CIECAM02 color appearance model by means of neural networks

An artificial neural network used to realize the approximating problem of the color appearance model (CAM) CIECAM02 in color management is demonstrated. GretagMacbeth ColorChecker Charts, which now are widely used in calibration of digital camera, are chosen as sanples to implement the forward and reverse color appearance models. When the predictive results are evaluated, for forward model, the output color appearance space is converted to the uniform color space based on CAM and is evaluated, while for reverse model, because the prediction precision is insufficient, we try to convert the color appearance space, which is the cylinder space, to the cube space similar to the red, green, and blue (RGB) space, and the results show that the precision is obviously improved.     

基于IMU的3D扫描仪倾角标定方法北大核心CSCD

3D扫描仪以精度高、速度快、自动处理、稳定性好等优势在场景三维重建、智能制造、自动驾驶、虚拟现实等领域得到了广泛的应用。目前3D扫描仪设备多是安装在三脚架上,容易因为地面不平使得扫描仪的转轴和重力方向产生夹角,最终导致拍摄出的全景图和点云倾斜,成为影响三维重建精度的关键难题。针对该问题,提出一种借助惯性测量单元标定3D扫描仪倾角的方法。该方法利用惯性测量单元输出的加速度信息,通过一个面阵相机建立惯性测量单元和3D扫描仪的联系,将惯性测量单元的加速度信息转到扫描仪的转轴上。利用该信息计算出扫描仪转轴与重力方向的夹角,并将该倾角补偿到生成的全景图和点云中,校正倾斜模型。通过实验对校正前后计算的角度进行对比,实验结果证明倾角测量误差可以控制在0.5°以内。并且经过标定后,精度至少提升20%,验证了整个标定方法的可靠性和准确性。     

A color image watermarking scheme based on hybrid classification method: Particle swarm optimization and k-nearest neighbor algorithm

In this paper, a novel robust watermarking technique using particle swarm optimization and k-nearest neighbor algorithm is introduced to protect the intellectual property rights of color images in the spatial domain. In the embedding process, the color image is separated into non-overlapping blocks and each bit of the binary watermark is embedded into the individual blocks. Then, in order to extract the embedded watermark, features are obtained from watermark embedded blocks using the symmetric cross-shape kernel. These features are used to generate two centroids belonging to each binary (1 and 0) value of the watermark implementing particle swarm optimization. Subsequently, the embedded watermark is extracted by evaluating these centroids utilizing k-nearest neighbor algorithm. According to the test results, embedded watermark is extracted successfully even if the watermarked image is exposed to various image processing attacks.     

The segmentation of timber defects based on color and the mathematical morphology

Wood has the texture of natural beauty and elegant color so that it can be widely used in the construction and furniture. So people put the special focus on the texture of wood and they are nearly particular about its color. According to the conventional segmentation method, the characteristics of the wood and the actual production process in a short time of the request, this paper presents a segmentation method of wood panel based on color difference and mathematical morphology. In the HSI space, it firstly focus on select morphological edge detection of H component and I component. Instead of considering the small pixel blocks, it uses median filter to clear it to retain accurate edge image. So edge detection is characterized by the H-component of the color model, then region growing is based on edge information, in order to overcome defects of pseudo edge. In this paper, it uses the boundary information to select seed points automatically, then it takes a regional model of the regional boundary for the region growing, and finally it splits out a defective portion of the timber well.     

非均匀性和彩色失真图像的同时补偿

针对CCD摄像机或扫描仪产生图像存在颜色偏差和非均匀性使图像质量下降 ,通过多元线性回归分析方法同时对图像的非均匀性和彩色失真进行补偿 ,使输出图像信号均匀且其色度值与输入信号的色度值相匹配。依据算法进行了仿真试验 ,结果表明补偿后图像与原图像相比大体相近 ,且比非均匀性校正和彩色校正分步进行方法计算量小 ,节省时间     

Constructing ultrasonic images of soft spherical scatterers

The paper considers specific features of ultrasonic visualization of gas bubbles in a liquid or a medium of like soft biological tissue type under conditions when the size of scatterers is comparable to the acoustic wavelength. It was proposed to use styrofoam specimens as the experimental model of stationary gas bubbles. Patterns of ultrasound scattering by a styrofoam sphere in water were obtained experimentally. It was shown that the measurement results agree well with the prediction of the classical theoretical model of scattering of a plane wave by a perfectly soft sphere. Several experiments were performed illustrating the specific features of visualizing millimeter-sized bubbles. A Terason commercial ultrasonic scanner was used; gelatin specimens with embedded styrofoam spheres served as the objects of study. The simulation and experimental results showed that when bubbles with diameters of <1 mm are visualized, it is impossible to measure the diameter of scatterers because bubbles of different diameters are imaged as bright spots of identical diameter, which is equal to the scanner resolution. To eliminate this difficulty, it is recommended to use the results of theoretical simulation performed in this study, which revealed a monotonic increase in the backscattered signal intensity with an increase in bubble radius. An ultrasonic visualization mode is proposed in which the brightness of scattered signals is used to differentiate between bubbles of different size.     

Development of a Single-Sided Nuclear Magnetic Resonance Scanner for the In Vivo Quantification of Live Cattle Marbling

Non-invasive in vivo marbling quantification helps owners to choose the optimum nutritional management for growing cattle and buyers to more precisely evaluate grown cattle at auctions. When using time-domain proton nuclear magnetic resonance (NMR) relaxometry, it is possible to quantify muscle and fat separately by taking advantage of the difference in the spin–spin relaxation time (T2) between water molecules in muscles and fat molecules, which would contribute to the non-invasive and objective determination of marbling scores. With this in mind, we developed a prototype NMR scanner (4.1 MHz for protons) using an original single-sided magnetic circuit and a plane radio frequency (RF) coil for use in the non-invasive quantification of water and fat in live cattle. The sensed region of the developed scanner is compact and almost cubical (19 × 19 × 16 mm³) while the investigation depth (the distance from the RF coil to the center of the sensed region) has been lengthened to 30 mm, which is sufficient for the in vivo trapezius muscle measurement of live cattle. Measurements of 17 samples of beef meat blocks kept at 39 °C were taken in a laboratory to successfully obtain the calibration lines used to convert the NMR signals into water and fat weight fractions at correlation coefficients in excess of 0.9. We also showed that each meat sample could be measured in about 10 s with a measurement error as small as approximately 10 wt%. Accordingly, we believe that our prototype scanner would be useful for in vivo marbling measurements of live cattle trapezius muscles.     

基于墨量限制样本的打印机光谱特性化模型修正方法

打印机色彩特性化是打印色彩管理技术的关键。打印机特性化模型修正,是指针对因打印介质及墨盒更换等原因而造成的特性化模型精度下降问题,借助特定修正样本实现原始模型精度校正的过程。为进一步提高此类修正方法的建模精度与效率,提出了一种基于墨量限制样本的打印机光谱特性化修正方法,该方法充分利用新介质墨量限制过程所制备的墨量限制样本,在无需额外修正样本的条件下,实现了原始特性化模型的有效修正。研究以三类不同类型打印介质为例,以现有典型特性化模型修正方法为对照,通过实验对本文方法的有效性进行了验证。结果显示,该方法相较现有方法展现出更为优异的修正效果,在无需额外修正样本的条件下,其光谱修正精度可提升15%～20%,色度修正精度可提升10%～20%,实现了修正精度与效率的同步优化。     

Four-quark mesonic states of low orbital excitations

A nonrelativistic potential model is used to describe the orbital excitations and color configuration mixing in four-quark mesonic states. Possible experimental structures to which some of the calculated states might correspond are briefly discussed.     

A novel methodology for photometric compensation of projection display on patterned screen

We propose a novel methodology based on the projector-camera (ProCam) system to address the photometric compensation issue for the projection display on the patterned screen.The patterned screen is treated as the combination of a perfect white screen and a color modulator.The perfect white screen is used to automatically and accurately characterize the ProCam system offline using the polynomial model,and the parameters of the color modulator can be efficiently recovered by employing only two gray images based on the linear reflectance model.The experimental results show that the color artifacts of the display image can be greatly improved with this methodology,which demonstrates its feasibility and validity in the photometric compensation.