英语翻译随着人类社会的进步,科学技术的发展,人们对信息处理和信息交流的要求越来越高.而今后的信息是以图像为主的多媒体信息

英语翻译
随着人类社会的进步,科学技术的发展,人们对信息处理和信息交流的要求越来越高.而今后的信息是以图像为主的多媒体信息.由于图像具有庞大的数据量,占有的空间和带宽大,难以存储和传输,这就要求在保证质量的前提下以较小的空间存储图像和较少的比特率传输图像,就需要采用图像压缩编码技术来实现.
本文首先简要介绍JPEG标准的发展历史并介绍了各种标准的特点,然后对JPEG图像压缩基础和必要性做了详细的阐述,并分析了图像压缩的基本原理、分类和评价标准等进行了介绍.重点介绍了JPEG压缩算法的过程和各种编码方法,分析了编码中离散余弦变换（DCT）、量化及反量化、熵编解码和差值预测编码等模块的原理和各模块的功能分析.并用matlab等软件对JPEG算法进行了仿真,将不同量化等级下得到的结果进行了比较.分析并改进了JPEG压缩算法中的DCT变换和量化过程,DCT过程采用DCT查表法代替DCT常规变化,达到减少计算机乘除运算次数的目的；量化过程由矢量量化代替标量量化,达到在保证最小失真度的前提下提高压缩比.
JPEG的成功是有目共睹的,目前Intenret上大多数图片是以JPEG的格式进行传播的.然而JPEG也是有明显缺点的,它在进行低频率下进行编码会产生严重的方块效应,且压缩速度也较慢.本文针对JPEG压缩时速率较慢的问题,利用查表法减少原DCT算法中大量的乘法运算,达到了提高压缩速度.

With the progress of human society, the development of science and technology, people on the information processing and information exchange and taller to the requirement of. And the information in the future is the image first multimedia information. Due to the large volume of data image possession, space and bandwidth is big, difficult to storage and transmission, it is required to quality premise with a small storage space images and less bits to rate transmission image, just need to adopt the image compression technology.
This paper first briefly introduces the development history of the JPEG standard and introduces the characteristics of various standards, and then to JPEG image compression base and necessity this paper expounds in detail, and analysis of the image compression the basic principles, classification and evaluation standard is described. Introduces the process of JPEG compression algorithm and all kinds of coding method, this paper analyzes the coding discrete cosine transform (DCT), quantitative and the quantization, entropy decoding and poor value forecast coding, and other modules of each module of the principle and function analysis. With matlab software such as JPEG arithmetic of the simulation, the different quantitative level the results were compared. Analysis and improved the JPEG compression algorithm and quantify the DCT transformation process, DCT process using DCT querying method instead of DCT normal changes so as to decrease the number of computer multiply and divide purpose; Quantization process by vector quantization instead of scalar quantitative, to ensure minimum distortion degree in the premise of improving compression ratio.
The success of the JPEG is obvious, at present the picture is most Intenret JPEG format to spread. However JPEG is also have obvious shortcomings, it in the low frequency code under may have a serious effect, and the square compression speed also slower. This paper in JPEG compression rate slower when the problem of querying method to reduce the DCT algorithm in large Numbers in multiplication, to improve the compression speed.