IEEE Trans Pattern Anal Mach Intell. 2017 Aug;39(8):1504-1517. doi: 10.1109/TPAMI.2016.2606397. Epub 2016 Sep 7.
In this paper, we introduce an automatic approach to generate trimaps and consistent alpha mattes of foreground objects in a light-field image. Our method first performs binary segmentation to roughly segment a light-field image into foreground and background based on depth and color. Next, we estimate accurate trimaps through analyzing color distribution along the boundary of the segmentation using guided image filter and KL-divergence. In order to estimate consistent alpha mattes across sub-images, we utilize the epipolar plane image (EPI) where colors and alphas along the same epipolar line must be consistent. Since EPI of foreground and background are mixed in the matting area, we propagate the EPI from definite foreground/background regions to unknown regions by assuming depth variations within unknown regions are spatially smooth. Using the EPI constraint, we derive two solutions to estimate alpha when color samples along epipolar line are known, and unknown. To further enhance consistency, we refine the estimated alpha mattes by using the multi-image matting Laplacian with an additional EPI smoothness constraint. In experimental evaluations, we have created a dataset where the ground truth alpha mattes of light-field images were obtained by using the blue screen technique. A variety of experiments show that our proposed algorithm produces both visually and quantitatively high-quality alpha mattes for light-field images.
在本文中，我们介绍了一种自动生成光场图像中前景对象的 Trimap 和一致 Alpha 遮罩的方法。我们的方法首先基于深度和颜色对光场图像进行二进制分割，粗略地将其分割为前景和背景。接下来，我们通过使用导向滤波器和 KL 散度分析分割边界处的颜色分布来估计准确的 Trimap。为了在子图像之间估计一致的 Alpha 遮罩，我们利用视差平面图像（EPI），其中沿相同视差线的颜色和 Alpha 必须一致。由于前景和背景的 EPI 在遮罩区域中混合在一起，因此我们通过假设未知区域内的深度变化在空间上是平滑的，将 EPI 从确定的前景/背景区域传播到未知区域。利用 EPI 约束，我们推导出两种解决方案，用于在已知和未知的视差线上的颜色样本时估计 Alpha。为了进一步增强一致性，我们使用带有附加 EPI 平滑约束的多图像遮罩拉普拉斯算子来细化估计的 Alpha 遮罩。在实验评估中，我们创建了一个数据集，其中使用蓝屏技术获得了光场图像的真实 Alpha 遮罩。各种实验表明，我们提出的算法为光场图像生成了高质量的视觉和定量 Alpha 遮罩。
