毕业设计（论文）外文翻译JPEG标准研究及算法实现

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1、JPEG2000图像压缩标准简介 郑州轻工业学院本科毕业设计（论文）英文翻译题 目 JPEG标准研究及算法实现 学生姓名 专业班级 电子信息07级1班 学 号 院 （系） 计算机与通信工程学院 指导教师 完成时间 2011 年4月10日 英文原文JPEG2000 image compression standard and characteristicsAbstractWith the development of the network and multimedia technologies , people need more and more images with high funct

2、ion and quantity , so the compressive image techniques require higher performance as well as new characteristics to satisfy some special use. For this , ISO released again a new static image compress technique - JPEG2000 , which may become the new image compression standard in the future.JPEG2000 is

3、 to adapt to the continuous development of image compression applications, the emergence of new still image compression standard. JPEG2000 image coding system describes the realization of the process, of which the basic algorithm used is described and key technologies, introduced the new standard fe

4、atures and applications, and its performance is analyzed. With the rapid growth of multimedia applications and networks continues to develop, the traditional JPEG compression technology has been unable to meet the peoples digital multimedia image data requirements, a more powerful and efficient supe

5、rior still image compression standard has been referred to the development agenda , this is a JPEG2000. 1. IntroductionJPEG (Joint Photographic Experts Group) is the International Organization for Standardization (ISO) developed under the leadership of the committee still image compression standard,

6、 the first set of international still image compression standard ISO 10918-1 (JPEG) is that established by the Committee. As the excellent quality JPEG, so that within a few years he was a great success, is widely used in the field of Internet and digital cameras on the site 80% have adopted the JPE

7、G image compression standard. However, the current JPEG still image compression standard, with mid-range and high-bit-rate on the rate distortion characteristics of a good, but in the context of low bit rate, there will be obvious blocking effects, its quality has become unacceptable . JPEG can not

8、be provided in a single stream lossy and lossless compression, and can not support more than 64 64 K of the image compression. At the same time, despite the current JPEG standard has a requirement to restart the interval, but when bit errors encountered when the image quality will be seriously damag

9、ed. To solve these problems, since March 1997 onwards, JPEG image compression standards committee started to develop a new generation of image compression standard to address these problems. In March 2000 the Tokyo conference to identify a new generation of color still image coding standard JPEG2000

10、 image compression coding algorithm. 2. JPEG2000 image compression standard profileJPEG2000 system is divided into the following seven parts: JPEG2000 image coding system Expansion (to the core of the definition add more features and sophistication); movement JPEG2000; consistency; reference softwar

11、e (now includes Java and C implementation); compound image file format (for document scanning and fax applications); of the minimum support to (technical report). as fully accredited ISO standard that defines the core compression and minimum file formats, definition of compression and expansion of f

12、ile formats. Which, has been finalized, and other are still in process. Discussed in this article is based on the JPEG2000 standard Part 1. In the encoder, firstly the source images of the result of the pre-treatment, to deal with the results of discrete wavelet transform, wavelet coefficients obtai

13、ned. Then the wavelet coefficients were quantizatived and entropy coding, the final composition of the standard output code stream (bit stream). Decoders are encoder reverse process,First to code flow unpack and entropy decoding, and then reverse to quantify and discrete wavelet inverse transform, i

14、nverse transform the results of the post-processing synthesis, we have reconstructed image data. Although JPEG2000 and JPEG encoding and decoding process is similar, there is a very big difference between the the concrete realization of each step. The general steps in the encoding process is as foll

15、ows: (1) composed of more than one color component image is decomposed into a single color component image. There are certain correlation between weight by decomposition related components, through the decomposition of the relevant components transform can reduce the redundancy between the data to i

16、mprove compression efficiency; (2) components of the image is decomposed into a rectangle the size of a unified piece - the image chip. Image film is transformed, and the basic unit of encoding and decoding;(3) Every image piece for wavelet transform. Generate multi-level factor image. The coefficie

17、nts of these different series, different images can be reconstructed resolution images;(4) the results of multi-level decomposition of wavelet coefficients is composed of multiple sub-band. They said that the film image local area (rather than the whole image) of the frequency characteristics; (5) s

18、ub-band coefficients to quantify, and the composition of a rectangular array of code block; (6) of a code block in the coefficient bit planes (a code block in the coefficient values have the same right to those bits) for entropy coding; (7) relative to the background of the image area can be carried

19、 out higher-quality region of interest coding; (8) through the reign stream by adding mask to increase the anti-interference; (9) each stream has one of the most anterior head structure, it describes the properties of the source image, various decomposition and coding style. The head structure can b

20、e used to locate, extract, decode and reconstruct images, images can be obtained with the desired resolution, reproducible precision, area of interest or other features. Encoding process is mainly divided into the following processes: pre-processing, core processing and bit-stream organization.The i

21、mage preprocessing part includes image segmentation, DC level (DC) displacement and weight change.Key processing in part by the discrete wavelet transform, quantization and entropy coding form. Bit-stream part of the organization include zoning, code blocks, layers and packages organization. 3 .Comp

22、arison between JPEG and JPEG 2000 JPEG 2000 offers numerous advantages over the old JPEG standard,. One main advantage is that JPEG 2000 offers both lossy and lossless compression in the same file stream, while JPEG usually only utilizes lossy compression4. JPEG does have a lossless compression engi

23、ne, but it is separate from the lossy engine, and is not used very often. Thus, when high quality is a concern, JPEG 2000 proves to be a much better compression tool. Because of the way the compression engine works, JPEG 2000 promises a higher quality final image, even when using lossy compression.

24、Since the JPEG 2000 format includes much richer content than existing JPEG files, the bottom line effect is the ability to deliver much smaller files that still contain the same level of detail as the larger original JPEG files. The JPEG 2000 files can also handle up to 256 channels of information a

25、s compared to the current JPEG standard, which, by reason of common implementation, is limited to only RGB (red, green, and blue) data. Figure 1 shows two images that were first compressed with the old JPEG compression engine, and then compressed using the JPEG 2000 method. The images that were comp

26、ressed using JPEG 2000 are seen from Figure 1 to retain a much higher quality.Figure 1 Comparison of two images compressed using JPEG and JPEG 2000A second advantage of JPEG 2000 over JPEG is that JPEG 2000 is able to offer higher compression ratios for lossy compression. For lossy compression, data

27、 has shown that JPEG2000 can typically compress images from 20%-200% more than JPEG. Compression efficiency for lossy compression is typically measured using the peak signal to noise ratio, or PSNR, and the root mean square error (RMSE). This method seeks to take into account the visual quality reta

28、ined by the compression method, as well as how much the image was compressed. The formula for the PSNR compression efficiency, in dB, is shown in (1), where b is the bit depth of the original image. An example of some PSNR efficiencies for JPEG 2000 and JPEG is shown in Table 1. Two different color

29、images were compressed using several different bit rates (measured in bits per bpp) using both JPEG 2000 and JPEG. A higher bit rate will result in a higher quality picture. The analysis was performed by Maryline Charrier, Diego Santa Cruz, and Mathias Larsson as part of an overview of JPEG 2000. Th

30、e results indicate that JPEG 2000 consistently offers a higher compression efficiency. One should note that since the PSNR is measured on a log scale, the data in Table 1 indicates that in actuality the test showed that JPEG 2000 compresses almost twice more than JPEG.Table 1 Comparison of PSNR comp

31、ression efficiencies(in dB)for two images at various bit ratesJPEG 2000 is also able to offer compression ratios of about 2.5:1 for lossless compression, whereas JPEG was not able to satisfactorily perform lossless compression at all. Lossless compression ratios are simply measured by how much less

32、memory the compressed image uses.Another advantage of JPEG 2000 is its ability to display images at different resolutions and sizes from the same image file. With JPEG, an image file was only able to be displayed a single way, with a certain resolution. Because JPEG 2000 is based on wavelets, the wa

33、velet stream can be only partially decompressed if the user only wants a low-resolution image, while the full resolution image can be viewed if this is desired. Figure 2 shows an image that is displayed at full size and full resolution, as well as half size and at a much lower resolution. All of the

34、 images came from a single JPEG 2000 file.Figure 2 Example of viewing a single JPEG 2000 file atdifferent resolutions and sizesHalf sizeFull size and full resolutionOne-tenth of the resolutionJPEG2000 advantages of its unique make up for deficiencies in the existing JPEG standard. Discrete wavelet t

35、ransform algorithm, the image can be converted into a series of pixels can be more effective memory module sub-band, therefore, JPEG2000 image compression format than the JPEG can be based on the current re-increased by 10% to 30%, and the compressed image appears to more delicate smooth. In other w

36、ords, online viewing of images using JPEG2000 compression, not only to download speeds faster than using JPEG format, nearly 30%, but the quality will be better. For the current JPEG standard, in the same compressed stream can not provide lossy and lossless compression, while in JPEG2000 systems, by

37、 selecting the parameters, can be lossy and lossless image compression, image quality to meet the demanding medical images, image library, etc. processing needs. Now the network is based on JPEG image download block transfers, so it can only be displayed line by line, while the use of JPEG2000 image

38、 format support for progressive transmission (Progressive Transmission), which allows the image resolution or pixels in accordance with the required accuracy of reconstruction, the user needed for image transmission control, in obtaining the required image resolution or quality requirements, can ter

39、minate the decoding, rather than receiving the entire image compression bit stream. Since JPEG2000 uses wavelet technology, using its local resolution properties, without extracting the case may be random access to some image region of interest (ROI) of the compressed stream of compressed image data

40、 transmission, filtering and other operations. 4. ConclusionJPEG2000 image compression for the 21st century, the development of new applications still image compression standard, which uses wavelet transform and the latest compression algorithm can not only obtain better compression ratio, but also

41、of the compression flow flexibility. Can be applied to the Internet, mobile communication, printing, scanning, digital photography, remote sensing, fax, health care, digital libraries and other aspects of image compression. However, the complexity of JPEG2000 and the required space was relatively la

42、rge, we need to be studied in the further.英文翻译：JPEG2000图像压缩标准简介摘要随着多媒体和网络的发展，人们对图像质量和图像功能的要求越来越高，这要求图像压缩技术不仅具有较高的压缩性能，且还应具有新的特征。为此 , 出现了新一代静止图像压缩技术JPEG2000 , 有可能成为未来新的图像压缩标准。JPEG2000是为适应不断发展的图像压缩应用而出现的新的静止图像压缩标准。阐述了JPEG2000图像编码系统的实现过程, 对其中采用的基本算法和关键技术进行了描述，介绍了这一新标准的特点及应用场合，并对其性能进行了分析。随着多媒体应用领域的快速增长和

43、网络的不断发展，传统的JPEG压缩技术已无法满足人们对数字化多媒体图像资料的要求，一种功能更强大、效率更卓越的静止图像压缩标准被提到制定日程上，这就是JPEG2000。1 引言JPEG（Joint Photographic Experts Group）是在国际标准化组织(ISO)领导之下制定静态图像压缩标准的委员会，第一套国际静态图像压缩标准ISO 10918-1(JPEG)就是该委员会制定的。由于JPEG优良的品质，使他在短短几年内获得了极大的成功，被广泛应用于互联网和数码相机领域，网站上80%的图像都采用了JPEG压缩标准。然而，目前的JPEG静止图像压缩标准,具有中端和高端比特速率上的良

44、好的速率畸变特性，但在低比特率范围内，将会出现很明显的方块效应，其质量变得不可接受。JPEG不能在单一码流中提供有损和无损压缩，并且不能支持大于6464 K的图像压缩。同时，尽管当前的JPEG标准具有重新启动间隔的规定，但当碰到比特差错时图像质量将受到严重的损坏。 针对这些问题，自1997年3月起，JPEG图像压缩标准委员会开始着手制定新一代的图像压缩标准以解决上述问题。2000年3月的东京会议，确定了彩色静态图像的新一代编码方式JPEG2000图像压缩标准的编码算法。2 JPEG2000图像压缩标准JPEG2000系统分为下列7个部分： JPEG2000图像编码系统 扩充(给的核心定义添加更

45、多的特征和完善度)； 运动JPEG2000； 一致性； 参考软件(目前包含Java和C实现)； 复合图像文件格式(用于文件扫描和传真应用程序)； 对的最小支持(技术报告)。 为完全被认可的ISO标准，定义了核心压缩技术和最小文件格式，定义压缩和文件格式的扩充。其中，已经制定完成，其余部分还在制定过程中。本文所讨论的JPEG2000标准就是基于第1部分的。在编码器中，首先对源图像进行前期预处理，对处理的结果进行离散小波变换，得到小波系数。然后对小波系数进行量化和熵编码，最后组成标准的输出码流（位流）。解码器是编码器的反过程，首先对码流进行解包和熵解码，然后是反向量化和离散小波反变换，对反变换的结

46、果进行后期处理合成，就得到重构的图像数据。尽管JPEG2000编解码过程与JPEG类似，但是对于每一步的具体实现两者却有非常大的差异。编码过程的一般步骤如下： (1) 将有多个颜色分量组成的图像分解成单一颜色分量的图像。分量之间存在一定的相关性，通过分解相关的分量变换，可减少数据间的冗余度，提高压缩效率； (2) 分量图像被分解成大小统一的矩形片图像片。图像片是进行变换和编解码的基本单元；(3) 每一个图像片进行小波变换。产生多级系数图像。这些不同级数的系数图像可以重构出不同分辨率的图像；(4) 多级分解的结果是由小波系数组成的多个子带。他们表示图像片中局部区域（而不是整幅图像）的频率特性；(

47、5) 对系数子带进行量化，并且组成矩形数组的码块；(6) 对一个码块中的系数位平面（也就是一个码块中整个系数中具有同样权值的那些位）进行熵编码；(7) 相对于图像的背景区域，可以对感兴趣区域进行更高质量的编码；(8) 通过在位流中加入掩码来增加抗干扰性；(9) 在每一个码流的最前部都有一个头结构，他描述的是源图像的属性，各种分解情况和编码风格。这个头结构可以用来进行定位、抽取、译码和重构图像，得到的图像可以具有所期望的分辨率、重现精度、感兴趣的区域或是其他特性。编码过程主要分为以下几个过程：预处理、核心处理和位流组织。预处理部分包括对图像分片、直流电平（DC）位移和分量变换。核心处理部分由离散

48、小波变换、量化和熵编码组成。位流组织部分则包括区域划分、码块、层和包的组织。3 比较JPEG和JPEG2000 标准的JPEG 2000拥有了比老一代的JPEG众多优势。 一个主要优点是JPEG 2000能在相同的文件流上提供有损和无损压缩，而JPEG格式通常只采用有损压缩。JPEG确实有一种无损的JPEG压缩引擎，但它是独立于有损发动机，而不是使用非常频繁。 因此，当高品质是一个问题，JPEG 2000的证明是一个更好的压缩工具。 由于引擎的工作方式压缩，JPEG 2000的承诺最终图像质量较高，即使使用有损压缩。 JPEG2000比现有的JPEG文件格式包括更丰富的内容，最明显的效果是在包

49、括相同的图像信息下比JPEG能够提供更小的文件。JPEG2000相比JPEG标准可以同时处理多达256个信息渠道，其中，共同实施的原因，仅限于RGB（红，绿，蓝）的数据。 图1显示了两个图片，第一次压缩是JPEG压缩引擎,然后利用JPEG 2000压缩方法。能从图1看到使用JPEG2000压缩图像保留更高的质量。 图1图像压缩比较两个使用JPEG和JPEG 2000 JPEG 2000第二个特点是能够提供较高的压缩比的有损压缩。 对于有损压缩，数据显示，JPEG 2000图像压缩通常可以超过JPEG的20-200以上。 有损压缩的压缩效率通常是使用峰值信噪比衡量，或信噪比和均方根误差（RMSE

50、）。 这种方法的目的，是追求在视觉上保证压缩质量的方法，以及最大化的压缩图像。该公式的信噪比表示压缩的效率，其中B是原始图像的位深度。 （1）JPEG 2000和JPEG的效率的信噪比见表1。同时使用JPEG 2000和JPEG两种不同的彩色图像压缩并用几种不同的比特率（bpp的测量每以位像素）。 较高的比特率将导致更高品质的图片。该分析是由Maryline Charrier，迭戈圣克鲁斯和Mathias拉尔森关于JPEG2000提出的部分观点。 结果表明，JPEG 2000能提供更高的压缩效率。 要注意的是，由于规模的PSNR测量记录，在现实的如表1的数据表明，JPEG 2000的压缩的JP

51、EG的两倍以上。 表1比较的PSNR的压缩效率 （分贝）两个在不同比特率图像 JPEG 2000是还可以提供压缩比约为2.5：1，无损压缩，而JPEG格式是无法令人满意地完成无损压缩。无损压缩率只是衡量在图像的压缩中损失多少内容。 JPEG2000文件另一个优点是在大小相同的图像上不同的分辨率的显示能力。 由于JPEG格式，图像文件只能显示具有一定的单一的方法。由于JPEG 2000是基于小波，小波流可以只部分压缩，如果需要用户只需要一个低分辨率的图像，而全分辨率的图像可以被看到。 图2显示了高分辨率图像，充分显示在全尺寸，半尺寸和低得多的分辨率的效果。 所有的图像来自一个JPEG 2000文

52、件。图2示例观看一个JPEG 2000文件在 一半大小全尺寸和全分辨率 十分之一的分辨率 JPEG2000以其特有的优点弥补了现行JPEG标准的不足。离散小波变换算法中，图像可以转换成一系列可更加有效存储像素模块的子带，因此，JPEG2000格式的图像压缩比可在现在的JPEG基础上再提高1030，而且压缩后的图像显得更加细腻平滑。也就是说，在网上观看采用JPEG2000压缩的图像时，不仅下载速率比采用JPEG格式的快近30，而且品质也将更好。对于目前的JPEG标准,在同一个压缩码流中不能同时提供有损和无损压缩,而在JPEG2000系统中,通过选择参数, 能够对图像进行有损和无损压缩,可满足图像

53、质量要求很高的医学图像、图像库等方面的处理需要。现在网络上的JPEG图像下载时是按块传输的，因此只能逐行地显示，而采用JPEG2000格式的图像支持渐进传输(Progressive Transmission),这就允许图像按照所需的分辨率或像素精度进行重构,用户根据需要,对图像传输进行控制,在获得所需的图像分辨率或质量要求后,便可终止解码,而不必接收整个图像的压缩码流。由于JPEG2000采用小波技术,利用其局部分辨特性,在不解压的情况下,可随机获取某些感兴趣的图像区域（ROI）的压缩码流,对压缩的图像数据进行传输、滤波等操作。4 结论 JPEG2000 是为21 世纪图像压缩应用制定的新的静止图像压缩标准，该标准采用小波变换和最新的压缩算法，不仅能够获得较好的压缩比，而且可对压缩流进行灵活处理。可应用于因特网、移动通信、打印、扫描、数字摄像、遥感、传真、医疗、数字图书馆等方面的图像压缩。但是JPEG2000 的复杂度及所需空间都比较大，有待于我们进一步研究。14