虚拟地形环境中高分辨率影像快速解压算法

虚拟地形环境具有广泛的应用,是高分辨率影像构成环境的可视化基础。影像精度提高所产生的庞大数据量使得读取和存储受限制,影响可视化系统的表现能力,因此数据压缩成为提高系统性能的有效手段。飞行器在低能见度条件下的山区高速低空飞行时,飞行员往往不知所处地形环境,存在潜在危险;与飞行员当前视点一致的虚拟地形环境能为其提供逼真的可视化场景,保持特殊条件下地形环境可见性。将影像数据经过提升小波变换到小波域,有效利用小波系数能量集中在低频子带以及子带间系数的相关性特点,将小波系数进行跨频带合理组织并矢量化,应用纹理压缩算法之一的矢量量化编码压缩小波系数,其压缩比大、非对称编码、解码速度快等特点适合飞行中对实时性的要求。

Fast Decompression Algorithm for High-resolution Texture Image in Virtual Terrain Environment

Virtual terrain environments have been used widely, and high-resolution texture images are of the foundation for visualization. Huge amount of data caused by the improvements on image resolution leads to the restriction of reading and storage which can influence the visualization system, data compression is an efficient means for boosting the system performance. When an aircraft is flying through a mountainous terrain at a high speed and low altitude under the condition of poor visibility, the manipulator usually gets disoriented where danger is likely to happen. The virtual terrain environment can provide the manipulator with a broad vision of the visual three-dimension geographical environment which keeps the visualization of terrain under special conditions. Based on the wavelet coefficients after lifting scheme, we firstly take the advantages of energy concentration on low-frequency sub-bands and relativity between sub-bands, then organize those coefficients across sub-bands and vectorize them, and again use one of the texture compression algorithm-vector quantization coding-for coefficients compression. This scheme is propitious for the real-time requirement in flight because of the high compression ratio, non-symmetrical coding and fast decoding speed.