By investigating the limitation of existing wavelet tree based image compression methods, we propose a novel wavelet fractal image compression method in this paper. Briefly, the initial errors are appointed given the ...By investigating the limitation of existing wavelet tree based image compression methods, we propose a novel wavelet fractal image compression method in this paper. Briefly, the initial errors are appointed given the different levels of importance accorded the frequency sublevel band wavelet coefficients. Higher frequency sublevel bands would lead to larger initial errors. As a result, the sizes of sublevel blocks and super blocks would be changed according to the initial errors. The matching sizes between sublevel blocks and super blocks would be changed according to the permitted errors and compression rates. Systematic analyses are performed and the experimental results demonstrate that the proposed method provides a satisfactory performance with a clearly increasing rate of compression and speed of encoding without reducing SNR and the quality of decoded images. Simulation results show that our method is superior to the traditional wavelet tree based methods of fractal image compression.展开更多
针对三维图形引擎中要生成具有相当真实感的场景的时候,由于场景本身的复杂性,要实现实时性较为困难。本文从场景的本身的几何特性入手,通过适当的方法来简化场景的复杂性,提出了一种动态的层次细节(Levels of De-tails)技术。通过实验...针对三维图形引擎中要生成具有相当真实感的场景的时候,由于场景本身的复杂性,要实现实时性较为困难。本文从场景的本身的几何特性入手,通过适当的方法来简化场景的复杂性,提出了一种动态的层次细节(Levels of De-tails)技术。通过实验表明本方法有良好的显示效果,同时具有较好的实时性,显示效果较好,且占用的存储空间不大。展开更多
为了实现高精度、流体阻力小的四岔管制造要求,采用了Pro/E软件基于特征参数化建模、Pro/E钣金设计的钣金特性及Pro/E的D raw ing模块等方法,分别完成了最佳三维实体的四岔管模型创建、组装,四岔管的分型平面展开及四岔管零件的2D工程...为了实现高精度、流体阻力小的四岔管制造要求,采用了Pro/E软件基于特征参数化建模、Pro/E钣金设计的钣金特性及Pro/E的D raw ing模块等方法,分别完成了最佳三维实体的四岔管模型创建、组装,四岔管的分型平面展开及四岔管零件的2D工程图。分析结果表明,利用该方法可以为中小型企业提供精确的生产用图,该设计降低了生产过程中的废品率,使设计者能运用该方法对相关岔管进行设计,提高了相关的设计能力。展开更多
基金Project 60571049 supported by the National Natural Science Foundation of China
文摘By investigating the limitation of existing wavelet tree based image compression methods, we propose a novel wavelet fractal image compression method in this paper. Briefly, the initial errors are appointed given the different levels of importance accorded the frequency sublevel band wavelet coefficients. Higher frequency sublevel bands would lead to larger initial errors. As a result, the sizes of sublevel blocks and super blocks would be changed according to the initial errors. The matching sizes between sublevel blocks and super blocks would be changed according to the permitted errors and compression rates. Systematic analyses are performed and the experimental results demonstrate that the proposed method provides a satisfactory performance with a clearly increasing rate of compression and speed of encoding without reducing SNR and the quality of decoded images. Simulation results show that our method is superior to the traditional wavelet tree based methods of fractal image compression.
文摘针对三维图形引擎中要生成具有相当真实感的场景的时候,由于场景本身的复杂性,要实现实时性较为困难。本文从场景的本身的几何特性入手,通过适当的方法来简化场景的复杂性,提出了一种动态的层次细节(Levels of De-tails)技术。通过实验表明本方法有良好的显示效果,同时具有较好的实时性,显示效果较好,且占用的存储空间不大。
文摘为了实现高精度、流体阻力小的四岔管制造要求,采用了Pro/E软件基于特征参数化建模、Pro/E钣金设计的钣金特性及Pro/E的D raw ing模块等方法,分别完成了最佳三维实体的四岔管模型创建、组装,四岔管的分型平面展开及四岔管零件的2D工程图。分析结果表明,利用该方法可以为中小型企业提供精确的生产用图,该设计降低了生产过程中的废品率,使设计者能运用该方法对相关岔管进行设计,提高了相关的设计能力。
