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文中研究了小波系数的统计特性 ,小波系数的均值、方差和能量 ,不同分辨率级相同方向上小波系数的关系 ,以及同一分辨率级不同方向的小波系数对图像主观质量的影响。从而为基于小波变换的图像数据压缩中的量化方法提供了依据 ,得到以下结论 :1 能量主要集中在低频系数 ,它对图像质量的影响最大 ,应对其进行精细量化 ;2 高频系数代表图像的细节信息 ,分辨率级越高的高频系数 ,对图像质量的影响越小 ,量化可以越粗 ;3 对同一方向不同分辨率级的高频系数 ,由于其相似性 ,可采用零树量化方法 ;4 在同一分辨率级 ,对角方向的系数对图像质量的影响最小 ,对角方向的系数量化最粗。
In this paper, the statistical properties of wavelet coefficients, the mean value of wavelet coefficients, variance and energy, the relationship of wavelet coefficients in the same direction at different resolution levels, and the influence of wavelet coefficients in different directions on the subjective quality of image are studied. This provides the basis for the quantization method of image data compression based on wavelet transform. The conclusions are as follows: 1 The energy is mainly concentrated in the low frequency coefficient, which has the greatest impact on the image quality, and should be finely quantized.2 The high frequency coefficient represents the image For detail information, the higher the resolution of the high-frequency coefficient, the smaller the impact on the image quality, the more quantitative; 3 high-frequency coefficients of different resolution levels in the same direction, due to their similarity, ; 4 at the same resolution level, the coefficient of diagonal direction has the least influence on image quality, and the coefficient of diagonal direction has the highest quantization.