【作者】 何忠平；

【导师】 张爱筠；

【作者基本信息】 哈尔滨工程大学 ， 模式识别与智能系统， 2004， 硕士

【摘要】 本文以电子文档格式PDF(Portable Document Format)为研究对象，以如何将图像数据保存到PDF中为研究重点，深入地研究了图像数据压缩在PDF中的应用。 首先，深入地研究了PDF的特点、生成方法和内部结构。 其次，围绕如何在Java环境下应用程序如何装载图像和提取图像数据，实现了一个能够支持任何图像类型装载的类。研究了图像像素数据提取方法，并用java语言编程实现了所提出的方法。 然后，围绕图像数据压缩技术如何在PDF应用，深入地研究了图像数据压缩技术，并重点研究了PDF的多个版本中都支持的图像数据压缩算法，其中包括融合了RLE、DCT、Huffman压缩方法的JPEG算法、ASCⅡ85和ASCⅡHex编码方法。在JPEG压缩的实现上，为了提高压缩效果和速度，本文在JPEG的DCT和量化两步中深入地分析了AA&N方法，并将其引入到具体的软件实现中。本文提出了具有自动识别图像类型，选择适合的压缩算法的自适应图像压缩编码技术，并将其用到图像数据写入PDF的实现中，取得了不错的效果。除此之外，针对图像数据写入PDF过程碰到的问题，给出了相应的解决方案。 最后，介绍集成了本文所有实现的测试系统。由所进行的两项实验结果可以说明本文所实现的算法的有效性。更多还原

【Abstract】 Portable Document Format (PDF) is the object to be studied in my paper, which is one of the electronic document formats. How to write image data to PDF is the focus of the study. Image data compression and its application in PDF are studied in-depth in the paper.At first, the characteristics and structure of PDF and approach to produce PDF are studied in detail.Secondly, focused on how to load image to application in the environment of Java, a class is realized, which can load any image by the same way. In addition, an approach to extract pixel value from loaded image is analyzed and the corresponding realization in Java is given.Then, with the topic of how to use image data compression in PDF, image data compression techniques are studied in the paper. Arithmetic of data compression or data encoding that used in several version of PDF is discussed. They include ASCII85,ASCIIHex and Joint Photographic Expert Group (JPEG) arithmetic which is composed of Run Length Encoding (RLE), Discrete Cosine Transform(DCT) and Huffman. In order to improve the efficiency and speed of compression, the AA&N method is used in the step of DCT and quantization which are two of the steps in the realization of JPEG. Adaptive Image Compression and Encoding (AICE) is proposed and used in the step of writing image data to PDF. It chooses fit arithmetic to process image data according to the type of image it recognized. A good result is obtained by imported AICE. Further, corresponding scheme to resolve the problems encountered in the process of writing image data to PDF is given.Finally, a test system integrated all above realization is introduced. Two experiment results show the efficiency of arithmetic we proposed.更多还原