在基于Retinex分解的低照度图像增强算法中,通过同时估计反射层和亮度层进行反射层恢复是一种流行且有效的方法,但算法结构较为复杂,实现难度大。这是因为恢复反射率是一个约束优化问题,不能用简单的优化技术来解决。本文提出了一种细...在基于Retinex分解的低照度图像增强算法中,通过同时估计反射层和亮度层进行反射层恢复是一种流行且有效的方法,但算法结构较为复杂,实现难度大。这是因为恢复反射率是一个约束优化问题,不能用简单的优化技术来解决。本文提出了一种细节显著性估计方法,可以利用简单的梯度下降优化技术从图像中恢复出反射层。该方法是基于我们所提出假设——暗区域近似(dark region approximation,DRA):由于低照度图像暗区域中的光照很弱,因此将其忽略不计,即将输入图像中暗区域的灰度分布直接近似为反射层。首先利用高斯场准则构建目标函数,通过基于DRA的Retinex模型估计细节显著层;然后用拟牛顿法求解该无约束优化问题;最后,从细节显著层中恢复出反射层作为最终增强结果。实验结果表明,与现有同类方法相比,我们的方法在增强效果和计算效率方面都具有优势。展开更多
Analyses of the correlation between hyperspectral reflectance and pigment content including chlorophyll a, chlorophyll b and carotenoid of leaves in different sites of rice were reported in this paper. The hyperspe...Analyses of the correlation between hyperspectral reflectance and pigment content including chlorophyll a, chlorophyll b and carotenoid of leaves in different sites of rice were reported in this paper. The hyperspectral reflectance of late rice during the whole growing season was measured using a Spectroradiometer with spectral range of 350-1050 nm and resolution of 3 nm. The chlorophyll a, chlorophyll b and carotenoid contents in rice leaves in rice fields to which different levels of nitrogen were applied were measured. The chlorophyll a content of upper leaves was well correlated with the spectral variables. However, the correlation between both chlorophyll b and caroteniod and the spectral variables was far from that of chlorophyll a. The potential of hyperspectral reflectance measurement for estimating chlorophyll a of upper leaves was evaluated using univariate correlation and multivariate regression analysis methods with different types of predictors. This study showed that the most suitable estimated model of chlorophyll a of upper leaves was obtained by using some hyperspectral variables such as SD r, SD b and their integration.展开更多
文摘在基于Retinex分解的低照度图像增强算法中,通过同时估计反射层和亮度层进行反射层恢复是一种流行且有效的方法,但算法结构较为复杂,实现难度大。这是因为恢复反射率是一个约束优化问题,不能用简单的优化技术来解决。本文提出了一种细节显著性估计方法,可以利用简单的梯度下降优化技术从图像中恢复出反射层。该方法是基于我们所提出假设——暗区域近似(dark region approximation,DRA):由于低照度图像暗区域中的光照很弱,因此将其忽略不计,即将输入图像中暗区域的灰度分布直接近似为反射层。首先利用高斯场准则构建目标函数,通过基于DRA的Retinex模型估计细节显著层;然后用拟牛顿法求解该无约束优化问题;最后,从细节显著层中恢复出反射层作为最终增强结果。实验结果表明,与现有同类方法相比,我们的方法在增强效果和计算效率方面都具有优势。
文摘Analyses of the correlation between hyperspectral reflectance and pigment content including chlorophyll a, chlorophyll b and carotenoid of leaves in different sites of rice were reported in this paper. The hyperspectral reflectance of late rice during the whole growing season was measured using a Spectroradiometer with spectral range of 350-1050 nm and resolution of 3 nm. The chlorophyll a, chlorophyll b and carotenoid contents in rice leaves in rice fields to which different levels of nitrogen were applied were measured. The chlorophyll a content of upper leaves was well correlated with the spectral variables. However, the correlation between both chlorophyll b and caroteniod and the spectral variables was far from that of chlorophyll a. The potential of hyperspectral reflectance measurement for estimating chlorophyll a of upper leaves was evaluated using univariate correlation and multivariate regression analysis methods with different types of predictors. This study showed that the most suitable estimated model of chlorophyll a of upper leaves was obtained by using some hyperspectral variables such as SD r, SD b and their integration.
