Single image dehazing algorithm based on the dark channel prior may cause block effect and color distortion.To improve these limitations,this paper proposes a single image dehazing algorithm based on the V-transform a...Single image dehazing algorithm based on the dark channel prior may cause block effect and color distortion.To improve these limitations,this paper proposes a single image dehazing algorithm based on the V-transform and the dark channel prior,in which a hazy RGB image is converted into the HSI color space,and each component H,I and S is processed separately.The hue component H remains unchanged,the saturation component S is stretched after being denoised by a median filter.In the procession of intensity component,a quad-tree algorithm is presented to estimate the atmospheric light,the dark channel prior and the V-transform are used to estimate the transmission map.To reduce the computational complexity,the intensity component I is decomposed by the V-transformfirst,coarse transmission map is then estimated by applying the dark channel prior on the low frequency reconstruction image,and the guided filter is finally employed to refine the coarse transmission map.For images with sky regions,the haze removal effectiveness can be greatly improved by just increasing the minimum value of the transmission map.The proposed algorithm has low time complexity and performs well on a wide variety of images.The recovered images have more nature color and less color distortion compared with some state-of-the-art methods.展开更多
Haze scatters light transmitted in the air and reduces the visibility of images.Dealing with haze is still a challenge for image processing applications nowadays.For the purpose of haze removal,we propose an accelerat...Haze scatters light transmitted in the air and reduces the visibility of images.Dealing with haze is still a challenge for image processing applications nowadays.For the purpose of haze removal,we propose an accelerated dehazing method based on single pixels.Unlike other methods based on regions,our method estimates the transmission map and atmospheric light for each pixel independently,so that all parameters can be evaluated in one traverse,which is a key to acceleration.Then,the transmission map is bilaterally filtered to restore the relationship between pixels.After restoration via the linear hazy model,the restored images are tuned to improve the contrast,value,and saturation,in particular to offset the intensity errors in different channels caused by the corresponding wavelengths.The experimental results demonstrate that the proposed dehazing method outperforms the state-of-the-art dehazing methods in terms of processing speed.Comparisons with other dehazing methods and quantitative criteria(peak signal-to-noise ratio,detectable marginal rate,and information entropy difference)are introduced to verify its performance.展开更多
Based on image segmentation and the dark channel prior,this paper proposes a fog removal algorithm in the HSI color space.Usually,the dark channel prior based defogging methods easily produce color distortion and halo...Based on image segmentation and the dark channel prior,this paper proposes a fog removal algorithm in the HSI color space.Usually,the dark channel prior based defogging methods easily produce color distortion and halo effect when applied on images with a large sky area,because the sky region does not meet the prior assumption.For this reason,our method presents a new threshold sky region segmentation algorithm using the initial transmission map of the intensity component I.Based on the segmentation result,the initial transmission map is modified in turn,and finally refined by the guided filter.The saturation components S is reconstructed using the low frequencies of the V-transform to reduce noise,and stretched by multiplying a constant related to the initial transmission map.Experimental results show that the proposed algorithm has low time complexity and compelling fog removal result in both visual effect and quantitative measurement.展开更多
目的为解决修复后的投影数据与周围投影数据之间过渡不连续的问题,提出一种基于正弦图融合的CT金属伪影校正算法。方法通过预处理和K均值聚类技术将具有相同空间信息的组织聚在一起生成先验图像,并根据金属区域与先验图像的投影差异校...目的为解决修复后的投影数据与周围投影数据之间过渡不连续的问题,提出一种基于正弦图融合的CT金属伪影校正算法。方法通过预处理和K均值聚类技术将具有相同空间信息的组织聚在一起生成先验图像,并根据金属区域与先验图像的投影差异校正原始图像投影以得到校正后的投影数据,最后采用滤波反投影算法重建得到校正后的CT图像。结果在CT仿真数据验证中,基于先验插值的金属伪影校正(Fusion Prior-Based Metal Artifact Reduction,FP-MAR)算法在单金属校正和多金属校正中的峰值信噪比分别为0.943和0.915,比线性插值校正金属伪影(Linear Interpolation Based Metal Artifact Reduction,LI-MAR)算法分别增加了28.65%和44.55%;FP-MAR算法在单金属校正和多金属校正中的结构相似性分别为0.984和0.961,比LI-MAR算法分别增加了48.41%和64.27%。临床CT伪影影像验证中,FP-MAR算法校正后CT金属伪影的主观评价高于LI-MAR算法校正后的CT金属伪影图像,且二者差异有统计学意义。结论本研究提出的算法可有效解决修复后的投影数据与周围投影数据之间过渡不连续的问题,更好地保留金属结构附近的信息。展开更多
As one of the most simple and effective single image dehazing methods, the dark channel prior(DCP) algorithm has been widely applied. However, the algorithm does not work for pixels similar to airlight(e.g., snowy gro...As one of the most simple and effective single image dehazing methods, the dark channel prior(DCP) algorithm has been widely applied. However, the algorithm does not work for pixels similar to airlight(e.g., snowy ground or a white wall), resulting in underestimation of the transmittance of some local scenes. To address that problem, we propose an image dehazing method by incorporating Markov random field(MRF) with the DCP. The DCP explicitly represents the input image observation in the MRF model obtained by the transmittance map. The key idea is that the sparsely distributed wrongly estimated transmittance can be corrected by properly characterizing the spatial dependencies between the neighboring pixels of the transmittances that are well estimated and those that are wrongly estimated. To that purpose, the energy function of the MRF model is designed. The estimation of the initial transmittance map is pixel-based using the DCP, and the segmentation on the transmittance map is employed to separate the foreground and background, thereby avoiding the block effect and artifacts at the depth discontinuity. Given the limited number of labels obtained by clustering, the smoothing term in the MRF model can properly smooth the transmittance map without an extra refinement filter. Experimental results obtained by using terrestrial and underwater images are given.展开更多
基金Supported by National Natural Science Foundation of China(61571046).
文摘Single image dehazing algorithm based on the dark channel prior may cause block effect and color distortion.To improve these limitations,this paper proposes a single image dehazing algorithm based on the V-transform and the dark channel prior,in which a hazy RGB image is converted into the HSI color space,and each component H,I and S is processed separately.The hue component H remains unchanged,the saturation component S is stretched after being denoised by a median filter.In the procession of intensity component,a quad-tree algorithm is presented to estimate the atmospheric light,the dark channel prior and the V-transform are used to estimate the transmission map.To reduce the computational complexity,the intensity component I is decomposed by the V-transformfirst,coarse transmission map is then estimated by applying the dark channel prior on the low frequency reconstruction image,and the guided filter is finally employed to refine the coarse transmission map.For images with sky regions,the haze removal effectiveness can be greatly improved by just increasing the minimum value of the transmission map.The proposed algorithm has low time complexity and performs well on a wide variety of images.The recovered images have more nature color and less color distortion compared with some state-of-the-art methods.
基金Project supported by the National Natural Science Foundation of China(Nos.U1664264 and U1509203)
文摘Haze scatters light transmitted in the air and reduces the visibility of images.Dealing with haze is still a challenge for image processing applications nowadays.For the purpose of haze removal,we propose an accelerated dehazing method based on single pixels.Unlike other methods based on regions,our method estimates the transmission map and atmospheric light for each pixel independently,so that all parameters can be evaluated in one traverse,which is a key to acceleration.Then,the transmission map is bilaterally filtered to restore the relationship between pixels.After restoration via the linear hazy model,the restored images are tuned to improve the contrast,value,and saturation,in particular to offset the intensity errors in different channels caused by the corresponding wavelengths.The experimental results demonstrate that the proposed dehazing method outperforms the state-of-the-art dehazing methods in terms of processing speed.Comparisons with other dehazing methods and quantitative criteria(peak signal-to-noise ratio,detectable marginal rate,and information entropy difference)are introduced to verify its performance.
基金Supported by the National Natural Science Foundation of China(61571046)the National Key Research and Development Program of China(2017YFF0209806)
文摘Based on image segmentation and the dark channel prior,this paper proposes a fog removal algorithm in the HSI color space.Usually,the dark channel prior based defogging methods easily produce color distortion and halo effect when applied on images with a large sky area,because the sky region does not meet the prior assumption.For this reason,our method presents a new threshold sky region segmentation algorithm using the initial transmission map of the intensity component I.Based on the segmentation result,the initial transmission map is modified in turn,and finally refined by the guided filter.The saturation components S is reconstructed using the low frequencies of the V-transform to reduce noise,and stretched by multiplying a constant related to the initial transmission map.Experimental results show that the proposed algorithm has low time complexity and compelling fog removal result in both visual effect and quantitative measurement.
文摘目的为解决修复后的投影数据与周围投影数据之间过渡不连续的问题,提出一种基于正弦图融合的CT金属伪影校正算法。方法通过预处理和K均值聚类技术将具有相同空间信息的组织聚在一起生成先验图像,并根据金属区域与先验图像的投影差异校正原始图像投影以得到校正后的投影数据,最后采用滤波反投影算法重建得到校正后的CT图像。结果在CT仿真数据验证中,基于先验插值的金属伪影校正(Fusion Prior-Based Metal Artifact Reduction,FP-MAR)算法在单金属校正和多金属校正中的峰值信噪比分别为0.943和0.915,比线性插值校正金属伪影(Linear Interpolation Based Metal Artifact Reduction,LI-MAR)算法分别增加了28.65%和44.55%;FP-MAR算法在单金属校正和多金属校正中的结构相似性分别为0.984和0.961,比LI-MAR算法分别增加了48.41%和64.27%。临床CT伪影影像验证中,FP-MAR算法校正后CT金属伪影的主观评价高于LI-MAR算法校正后的CT金属伪影图像,且二者差异有统计学意义。结论本研究提出的算法可有效解决修复后的投影数据与周围投影数据之间过渡不连续的问题,更好地保留金属结构附近的信息。
基金supported by the National Natural Science Foundation of China (No.61571407)。
文摘As one of the most simple and effective single image dehazing methods, the dark channel prior(DCP) algorithm has been widely applied. However, the algorithm does not work for pixels similar to airlight(e.g., snowy ground or a white wall), resulting in underestimation of the transmittance of some local scenes. To address that problem, we propose an image dehazing method by incorporating Markov random field(MRF) with the DCP. The DCP explicitly represents the input image observation in the MRF model obtained by the transmittance map. The key idea is that the sparsely distributed wrongly estimated transmittance can be corrected by properly characterizing the spatial dependencies between the neighboring pixels of the transmittances that are well estimated and those that are wrongly estimated. To that purpose, the energy function of the MRF model is designed. The estimation of the initial transmittance map is pixel-based using the DCP, and the segmentation on the transmittance map is employed to separate the foreground and background, thereby avoiding the block effect and artifacts at the depth discontinuity. Given the limited number of labels obtained by clustering, the smoothing term in the MRF model can properly smooth the transmittance map without an extra refinement filter. Experimental results obtained by using terrestrial and underwater images are given.
