专业英语-imageandtelevisions.ppt

Specialized English on Telecommunication,Yang XiaoQing,Key terms Picture element; the smallest resolved area in a video scanning technique Pixel Shade 颜色深浅，渐变 Histogram 直方图 Reassign 再分配 A portion of a TV signal, transmitted by frequency modulation Aural signal a portion of a TV signal, which is amplitude modulated onto a carrier Video signal,Unit 17 Images and Televisions,Time-lapsed 时间上相继的 the branch of pure mathematics dealing with the theory of numerical calculations Arithmetic bend out of shape Warping 扭曲，变形 a computer method that is used to make one image gradually change into a different one Morph 变体,变种 the act of expanding an aperture Dilation Erosion 腐蚀 make unclear Blur Kernel 核心，要点 the size of something as given by the distance around it Perimeter 周长,Rows and columns 图像的行和列 Gray scale image 灰度图像 Gray scale level 灰度级 Image contrast 图像对比度 Bar graph 条形图 Histogram equalization 直方图均衡 Resultant matrix 结果矩阵 Edge detection 边缘检测,Object recognition 目标识别 Magnitude spectrum 幅度谱 Phase spectrum 相位谱 CT Computed tomography 计算机层析 MRI Magnetic resonance imaging 核磁共振成像 Run length encoding 行程编码 Huffman encoding 哈夫曼编码 DCT Discrete cosine transform 离散余弦变换,a numerical measure of the uncertainty of an outcome Entropy Correlation 相关性 a grouping of a number of similar things Cluster Asymmetric 不对称的 Code book 码本 Fractal 分形 High definition television 高清晰度电视 RMS Root mean square 均方根 GIS Ground instrument system 地面测量系统 Vector quantization 矢量量化,Filter in a TV transmitter that allows both the video AM signal and audio FM signal to feed the same antenna Diplexer 天线公用器 A light-sensitive chip used to convert optical images to an electronic form CCD Charge couple device The time it takes an electron beam to move from the end of one line to the start of the next time Retrace interval (回程间隔) In a TV picture, the ratio of frame width distance to frame height distance Aspect ratio,Length of time an image stays on the screen after the electrical signal is removed Persistence Front end of a TV receiver that selects desired station Tuner Extremely high-Q filters often used in TV and radar applications Surface acoustic wave filters High-Q band stop circuit that attenuates a narrow band of frequencies Wavetrap Trap Another name for wavetrap Black-and-white TV Monochrome,Passage B compression/decompression techniques,Numerous methods have been developed for the compression of digital image data. 对于数字图像数据的压缩，人们已经研究出大量的方法。 One of the principal drivers for this development is the television industry where quality image data must be transferred to receivers using relatively simple equipment. 主要动力之一就是必须将高画质图像数据用相对简单的设备传送给接收机的电视。,The development of high definition television is further focusing the attention of industry and university scientists toward problems of data reduction and digital transmission. 高清晰度的电视的发展正进一步吸引工业界和研究人员致力于数据压缩和数字传播的研究。,The principal evaluation criteria for the analysis of compressed versus uncompressed imagery is whether a person can tell the difference between the images. 评价压缩图像和未压缩图像的主要标准是人们是否能区分它们。 A more implemental measure is the Root Mean Square (RMS) error between the original image and the image that has been compressed. 更有效的度量方法则是原始图像与压缩图像之间的均方根差。,Compression rates may be generated by determining the size of the compressed image in terms of number of bits per image pixel for the original image. 决定压缩图像尺寸的压缩比可以通过原始图像各像素所需压缩的比特数来确定。 Here we only considers compression of single high resolution multi-spectral images. 在此，先只考虑单个高分辨率多谱图像的压缩。,Higher compression rates will be achieved in a motion sequence where frame to frame variations may be quantified and only the changes from a reference image need be coded. 更高的压缩比可从运动序列的一帧到另一帧的变化量化获得，并且只对参考图像的变化部分进行编码。,There are two general types of compression: (1)loss-less, and (2) loss. Loss-less compression means that you can achieve a certain compression factor and be able to exactly reproduce the original image. 通常有两种压缩方法：非损失性压缩和损失性压缩。非损失性压缩意味着能产生某个压缩系数并可以完全复现原始图像。 Loss compression on the other hand allows some loss, but has the potential for much higher compression rates. 损失性图像压缩则允许某些图像信息丢失，但在压缩比上有着更大的潜力。,No matter what technique that you use, the exact rate is very dependent on the complexity of the image that you are analyzing. 无论你采用什么技术，准确的压缩率室依靠于你所分析的图像的复杂程度的。 For example, the normal best that can be achieved with loss-less encoding in a rate of 2 bits per pixel. 例如，通常非损失性编码能产生最好的效果是各像素2位的压缩比。,In fact, for some land-sat scenes with urban areas and many small farms, the factor of 2 bits per pixel may not be able to achieved. 实际上，对于很多农场的乡村卫星图像，用各像素2位的系数就不能够实现。 The same technique applied to a land-sat image of the mid-west where large fields occur and few shadows exist in images might produce a much better compression. 但对于大片开阔地和少数阴影的中西部地区的卫星图像，同样的技术能产生较好的压缩。,One loss-less technique is known as run length encoding. 有一种非损失性压缩技术称为行程编码。 The compression algorithm processes each line of input imagery looking for regions in which data values are the same. 该压缩算法对每一行输入图像进行处理以找出数据值一致的范围。,If ten pixels in the original image have a value of 10, then the same data may be represented as a data value, 10, and a multiplier saying how many times the value is repeated before a changed value. 如果原始图像中的10个像素值为10，那么相同的数据可被表示成同一数值：10，并且一个乘法器将指出该值在改变之前重复了多少次。 Huffman encoding follows a similar process. 哈夫曼编码就使用了相似的方法。,These loss-less techniques are generally called entropy coding techniques, and have application in document imaging, desktop publishing, and GIS. 这些非损失性技术通常称为熵编码技术并已经在档案图像、桌面出版和地理信息系统上得到应用。 It should be noted that entropy coding does not work exceptionally well in the representation of remote sensing images. 应该注意，熵编码在遥感图像的表示中并不是特别令人满意。,In remote sensing imagery it is well known that there may be significant correlation between different bands of multi-spectral data. 众所周知，在遥感图像中，在不同频谱的多谱数据之间可能存在显著的相关性。 In image processing, a procedure called principal components has been designed to identify correlation between image bands and to create a new set of transformed bands that represent a new color space in which the new image bands are uncorrelated. 在图像处理过程中，一个称为主分量的过程被设计用以确认图像频谱之间的相关性，并产生一组新的变换频谱,新图像频谱互不相关地表示一个新的彩色空间.,The procedure also provides a measure of the percent of the original variation present in the original image as found in each of the new transformed bands. 它也提供一个测量在每一种新变换频谱中，有多少原始图像变化的百分比的方法。 For Land-sat TM data, three to four of the transformed images represent 98 percent of the variance in the original images; therefore, a compression factor of 2 would be achieved with little loss. 对于卫星图像的遥测数据，34的变换图像表示了原始图像中的98的变化，因此，2位压缩系数只产生很小的损失。,Another type of transformed coding does not involve a rotation of the color space, but instead represents images in terms of spatial frequency of certain base functions. 另一种变换编码不涉及彩色空间的变化，但代之以某个基本函数的空间频率来表示图像。 Fourier Transforms map an image into a spatial frequency image into a spatial frequency image base on sin and cosine functions. A fast computer implementation of the Discrete Fourier Transform (DFF) is known as a Fast Fourier Transform (FFT). Discrete Cosine(DCT s) maps the same image to a spatial frequency image based only on the cosine function. 傅立叶变换将一个图像映射成一个基于正弦和余弦函数的空间频率图像。离散傅立叶变换(DFr)的快速计算机实现被称为快速傅立叶(FFr)。离散余弦变换(DCTS)将同一图像映射成只基于余弦函数的空间频率图像。,Each pixel may be represented by a series of trigonometric functions and coefficients derived from the images. If all terms of the transform s trigonometric functions are used, compression is minimal. 每一个像素可由一系列三角函数表示，系数则从图像导出。如果使用变换的三角函数所有的项，压缩是最小限度的。 As more terms are deleted, compression goes up, but the resulting compressed image develops certain artifacts of the procedure. 省略的项越多，压缩越大，但最终压缩图像会产生某些处理过程的人工痕迹。,Vector Quantization (VQ) is a type of encoding that defines a vector representation of non - over-lapping area blocks within an image. 矢量量化(VQ)是一种通过在图像中定义一个非重叠区域的矢量表达式来进行编码的方法。 A vector consists of values representing the data values for each pixel within the region. 矢量由区域内每个像素数据值的量值组成。,Using these vectors, clusters of vectors are derived using a derived spectral distance measure. 使用这些矢量，用一个导出的频谱距离可推导出矢量簇。 A codebook consisting of the clustered vectors is stored, representing the characteristics of the image. 由存储的一簇矢量组成的一个码本表示图像的特征。 This process is numerically intensive and may be iterative. 这个过程在数值上是密集且可重复的。,The decoder for VQ takes an image vector and compares it to stored vectors in the codebook. VQ的译码用一个图像矢量与码本中存储的矢量比较。 A selection is made based on minimization of a distortion function between the new vector and the codebook. 在新矢量和码本之间可根据失真函数的最小值进行选择。,The VQ technique can generally achieve compression ratios of between 20 to one and 35 to one with little observable distortion. VQ技术通常能在很难观察到失真的情况下达到30：1和35：1的压缩比 The VQ technique is an example of asymmetric compression in that considerably more time is spent deriving the codebook than in decompression via a codebook lookup. VQ技术是将大量时间用于推导码本而不是通过码本的查找来进行解压缩的不对称压缩的一个实例。 Since different images may have different characteristics, a robust codebook is necessary to successfully code and decode Landsat and other satellite images. 对于不同的图像有着不同的特征。要成功地对地球资源卫星和其他卫星图像进行编码和解码，就必须有一个稳定的码本。,A VQ technique using between channel correlation as well as spatial correlation achieves higher compression rates with less loss than independent band VQ. 用于信道相关以及空间相关之间的VQ技术在较