基于光场相机的四维光场图像水印及质量评价

Watermarking Scheme for Four Dimensional Light Field Imaging Based on Light Field Camera and Its Evaluation

光场相机通过在主镜组和传感器间特定位置设置微透镜阵列,在采集物方光强的同时可记录光线方向。提出一种在频域内对光场相机获取的四维光场图像加密的图像数字水印方法。植入信息经Base64编码后生成二维图像,并通过Aronld迭代对此图像进行均匀化处理,建立与原始光场坐标系匹配的虚拟计算光场,在四维傅里叶域内以切片替换的方式将加密信息植入原始光场中,实现光场图像加密,然后,基于二者坐标对应关系,应用傅里叶逆变换提取加密光场图像中的植入信息。搭建光场采集系统,应用本文方法对采集的原始光场图像进行加密处理。实验结果表明,加密光场图像信噪比高,与原始光场图像相关性强,加密光场图像无明显伪迹和失真,算法简便快捷,稳定可靠。

The light field camera can capture direction and intensity of light rays at the same time,when setting a lenslet array at a specific position between the primary mirror group and the sensor.We propose an image digital watermarking method for four-dimensional light field image obtained by the light field camera in the frequency domain.In this method,the embedded information is compiled by Base64 to generate a two-dimensional image,and then a virtual computational light field matching the original light field coordinates is established based on the image scrambled by Aronld cat map.A slice of frequency domain is obtained from virtual computational light field after the four-dimensional Fourier transform.By means of slice substitution,the information is embedded into original light field,in order to realize the aim of encrypting light field image.Finally,the watermark information is extracted successfully,by means of the Fourier inverse transformation and image binarization.A light field acquisition system is built,and a light field image is encrypted by the proposed method.The experimental results show that the encrypted light field has a high signal-to-noise ratio and strong correlation with the original light field.The proposed method is simple,fast,and reliable.There is no obvious artifact and distortion in the encrypted light field image.