Most approaches to estimate a scene’s 3D depth from a single image often model the point spread function (PSF) as a 2D Gaussian function. However, those method<span>s</span><span> are suffered ...Most approaches to estimate a scene’s 3D depth from a single image often model the point spread function (PSF) as a 2D Gaussian function. However, those method<span>s</span><span> are suffered from some noises, and difficult to get a high quality of depth recovery. We presented a simple yet effective approach to estimate exactly the amount of spatially varying defocus blur at edges, based on </span><span>a</span><span> Cauchy distribution model for the PSF. The raw image was re-blurred twice using two known Cauchy distribution kernels, and the defocus blur amount at edges could be derived from the gradient ratio between the two re-blurred images. By propagating the blur amount at edge locations to the entire image using the matting interpolation, a full depth map was then recovered. Experimental results on several real images demonstrated both feasibility and effectiveness of our method, being a non-Gaussian model for DSF, in providing a better estimation of the defocus map from a single un-calibrated defocused image. These results also showed that our method </span><span>was</span><span> robust to image noises, inaccurate edge location and interferences of neighboring edges. It could generate more accurate scene depth maps than the most of existing methods using a Gaussian based DSF model.</span>展开更多
目的针对运动模糊图像复原中,传统频谱法存在的检测误差大、抗噪性弱及有效检测范围有限等问题,本文提出一种融合高斯拉普拉斯(Laplacian of Gaussian,LoG)滤波与Radon变换的边缘增强频谱分析法,旨在实现点扩散函数(point spread functi...目的针对运动模糊图像复原中,传统频谱法存在的检测误差大、抗噪性弱及有效检测范围有限等问题,本文提出一种融合高斯拉普拉斯(Laplacian of Gaussian,LoG)滤波与Radon变换的边缘增强频谱分析法,旨在实现点扩散函数(point spread function,PSF)参数的精准估计。方法基于脑部MRI仿真运动模糊模型,分析频谱中明暗条纹的分布特征,采用LoG滤波提取频谱亮条纹边缘,抑制中心宽条纹与Gibbs现象导致的干扰,生成保留方向特征的离散边缘点集;利用Radon变换包容非共线点集的抗噪特性(离散边缘点沿角度θ投影时,真实边缘贡献相干叠加,噪声点投影随机抵消),显著提升峰信噪比,进而精准定位模糊角度并计算模糊长度;采用配对t检验,对传统中心亮条纹检测方法与本文方法的PSF参数估计误差进行统计学分析比较。结果本研究方法的角度估计平均误差0.08°,显著低于传统方法的3.28°,长度估计平均误差0.15像素,传统方法为0.88像素,有效角度检测范围由传统方法的±60°扩展到0~180°,且组间误差差异均达极显著水平(P<0.001)。结论本方法通过LoG滤波与Radon变换的协同机制,避免了对中心条纹完整性的依赖,解决了宽条纹导致的检测失效问题,同时有效抑制了噪声和Gibbs现象导致的干扰,显著提高了运动模糊PSF参数估计的精度与鲁棒性,为医学影像运动伪影消除提供可靠的技术基础。展开更多
文摘Most approaches to estimate a scene’s 3D depth from a single image often model the point spread function (PSF) as a 2D Gaussian function. However, those method<span>s</span><span> are suffered from some noises, and difficult to get a high quality of depth recovery. We presented a simple yet effective approach to estimate exactly the amount of spatially varying defocus blur at edges, based on </span><span>a</span><span> Cauchy distribution model for the PSF. The raw image was re-blurred twice using two known Cauchy distribution kernels, and the defocus blur amount at edges could be derived from the gradient ratio between the two re-blurred images. By propagating the blur amount at edge locations to the entire image using the matting interpolation, a full depth map was then recovered. Experimental results on several real images demonstrated both feasibility and effectiveness of our method, being a non-Gaussian model for DSF, in providing a better estimation of the defocus map from a single un-calibrated defocused image. These results also showed that our method </span><span>was</span><span> robust to image noises, inaccurate edge location and interferences of neighboring edges. It could generate more accurate scene depth maps than the most of existing methods using a Gaussian based DSF model.</span>
文摘目的针对运动模糊图像复原中,传统频谱法存在的检测误差大、抗噪性弱及有效检测范围有限等问题,本文提出一种融合高斯拉普拉斯(Laplacian of Gaussian,LoG)滤波与Radon变换的边缘增强频谱分析法,旨在实现点扩散函数(point spread function,PSF)参数的精准估计。方法基于脑部MRI仿真运动模糊模型,分析频谱中明暗条纹的分布特征,采用LoG滤波提取频谱亮条纹边缘,抑制中心宽条纹与Gibbs现象导致的干扰,生成保留方向特征的离散边缘点集;利用Radon变换包容非共线点集的抗噪特性(离散边缘点沿角度θ投影时,真实边缘贡献相干叠加,噪声点投影随机抵消),显著提升峰信噪比,进而精准定位模糊角度并计算模糊长度;采用配对t检验,对传统中心亮条纹检测方法与本文方法的PSF参数估计误差进行统计学分析比较。结果本研究方法的角度估计平均误差0.08°,显著低于传统方法的3.28°,长度估计平均误差0.15像素,传统方法为0.88像素,有效角度检测范围由传统方法的±60°扩展到0~180°,且组间误差差异均达极显著水平(P<0.001)。结论本方法通过LoG滤波与Radon变换的协同机制,避免了对中心条纹完整性的依赖,解决了宽条纹导致的检测失效问题,同时有效抑制了噪声和Gibbs现象导致的干扰,显著提高了运动模糊PSF参数估计的精度与鲁棒性,为医学影像运动伪影消除提供可靠的技术基础。
