单幅航片的薄云去除方法

Single Aerial Photo Cloud Removal

与匀质的雾霾不同,航摄像片中的絮状薄云形态多变、厚薄不均,航片的薄云去除比图像去雾更具挑战性.针对单幅航片中的薄云,提出一种基于分治思想的云去方法.首先设计一种基于颜色衰减先验、表征薄云覆盖程度的遮罩指数,并依据该指数将含云航片分割为遮罩层次不同的区块,使区块内的薄云近乎均匀、满足传输率光滑的假设;然后以改进的颜色线方法分别计算各区块内的大气光值,构成整幅图像的大气光图;再应用基于边界约束的传输率估算法计算粗略传输图;最后以加权L1范数作规则化项对粗略传输图进行优化,获得精细传输图,结合含云图像、大气光图与精细传输图反求理想条件下的航摄图像.在单机环境下进行单幅航片的薄云去除的实验结果表明,该方法能够大幅消减甚至完全去除絮状薄云对航片的遮罩影响,有效地增强图像可见性.

Due to non-uniformity,cloud in an aerial photo is even harder to remove than haze.This paper proposes a divide-and-conquer based method of cloud removal using a single aerial photo.Based on color attenuation prior,we design a veiling index that indicates the local concentration of cloud on the aerial photo.By this index,an image veiled by cloud was segmented into various regions of various extents of veiling.Each region was veiled by nearly uniform cloud,and thus subjected to commonly used assumption such as boundary constraint on transmission in image patches.Atmospheric light vectors in each region were estimated by modified color-lines model and then composed into a spatially varying airlight map for the whole image.Initial estimated scene transmission was further optimized by a weighted L1-norm based contextual regularization,which was used to obtain scene reflection image thereafter.We demonstrate the effectiveness of our cloud removal method on a number of example aerial photos containing cloud and compare our results with that of existing relevant methods.