Research on Non-local Multi-scale Fractional Differential Image Enhancement Algorithm
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摘要: 为了更好增强图像中的有用信息,改善图像视觉效果,该文提出了一种基于非局部多尺度分数阶微分图像增强算子(NMFD)。该算子首先将图像分成若干块子图像,计算每一块子图像的边缘强度系数、熵值和粗糙度等细节特征,将得到的特征数据在全局图像范围进行统一尺度的归一化,然后对这些归一化的数据进行加权求和作为图像的非局部特征值,最后利用指数函数建立图像细节特征和分数阶微分算子阶次之间的非线性量化关系,在不同的图像子块区域,确定不同尺度的分数阶微分阶次,实现图像的非局部多尺度增强。
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关键词:
- 图像增强 /
- 非局部多尺度分数阶微分算子 /
- 图像熵值 /
- 图像对比度
Abstract: In order to enhance the useful information in the image and improve the visual effect of the image, a Non-local Multi-scale Fractional Differential(NMFD) image enhancement operator is proposed. The operator divides the image into several sub-images and calculates the edge intensity coefficient, entropy value and roughness of each sub-image, and the obtained feature data are normalized in a unified scale in the global image range. Then, the normalized data are weighted to be the non-local eigenvalues of the image. Finally, an exponential function is used to establish the non-linear quantization relationship between image detail features and the value of fractional order. Thus, the fractional order of different scales can be determined in different image sub-block regions, so that the non-local multi-scale image enhancement model is realized. -
表 1 NMFD增强模型在不同窗口尺寸下实验数据对比
窗口数量 平均梯度 边缘保持系数 对比度 熵 2×2 11.3139 1.7529 0.8152 7.5301 4×4 11.6058 1.8011 1.0725 7.5524 8×8 12.4049 2.0808 1.0893 7.5829 16×16 13.5831 2.4982 1.8659 7.5966 32×32 15.6209 2.9672 1.9856 7.5686 表 2 不同方法的图像增强模型增强lena图像的实验数据对比
增强类型 平均梯度 边缘保持系数 对比度 熵 Laplace 10.9327 2.1957 1.3521 7.1963 G-L 10.8623 1.7908 0.9982 6.8723 HE 10.7522 1.4451 0.7538 5.9849 CLAHE 12.4368 1.8789 0.9823 7.3692 NMFD 14.2039 2.2321 1.3640 7.7404 -
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