专业外语-Multimedia-Image.ppt

Lecture 16：Introduction to multimedia: image 2013.6 Outline Background Text tour Vocabulary Difficult point Text 英译汉 汉译英 Background 图像的基础知识： 图像分辨率(Resolution): row, column 灰度等级: Gray scale levels 图像通道(Channel): 彩色图像(RGB，3通道), 灰度图像(Gray scale ，1通道) 图像直方图(Histogram) 图像压缩(Image Compression) 图像制式(Image format) 图像处理算法：直方图均衡化 A digital image：Lena.jpg Image Resolution: 512×512 (in pixel) One channel: 8Bits Original size: 256K Bytes Size after compreesion: 158771 Bytes As standard test image from USC since 1973 图像压缩与格式 位图（Bit map）：bmp 无损压缩（TIFF: Tagged Image File Format） 有损压缩（JPEG：Joint Photographic Experts Group） 图像大小的计算：Row×Column×Bits/pixel, 其中 Row×Column=Number of pixels JPEG技术 以一幅24位彩色图像为例，JPEG的压缩步骤分为： 1.　颜色转换 2.　DCT变换 3.　量化 4.　编码，其中编码过程有以下： Z字形编码； 使用DPCM对直流系数(DC)进行编码； 使用RLE对交流系数(AC)进行编码； 直方图均衡化 原始图像及其直方图 均衡化图像及其直方图 Paragraph 1 A digital image is made up of many rows and columns of pixels. For gray scale images, each pixel is assigned a number that represents the gray shade assigned to that pixel. The larger the number of the pixels in an image, the larger the number of available gray scale levels, the better the resolution of the image. The following image is an 8-bit images, with 2^8=256 possible gray scale levels. The number of row and column are 808×562 (Figure 22.1) Vocabulary Digital image: 数字图像 Row：行 Column：列 Pixel: 像素 shade: 色调明暗 Gray: 灰度 Assign: 分配，赋值 Resolution: 图像分辨率 Difficult point A digital image is made up of many rows and columns of pixels. made up of: 由...组成 翻译：数字图像是由众多行与列的像素组成的。 Difficult point The following image is an 8-bit images, with 2^8=256 possible gray scale levels. 8-bit image: 八位（比特）的图像 Gray scale levels: 灰阶，灰度等级 翻译：下面这张图像是一个八位的图像，也就是说包含了256个灰度等级。 Difficult point The larger the number of the pixels in an image, the larger the number of available gray scale levels, the better the resolution of the image. the larger … the better … ： …越大…越好 翻译：图像上的像素越多，灰度等级越多，图像的分辨率就越好。 Paragraph 2 The gray scales present in a digital image can be