NASA Langley Res. Center, Hampton, VA.
IEEE Trans Image Process. 1997;6(3):451-62. doi: 10.1109/83.557356.
The last version of Land's (1986) retinex model for human vision's lightness and color constancy has been implemented and tested in image processing experiments. Previous research has established the mathematical foundations of Land's retinex but has not subjected his lightness theory to extensive image processing experiments. We have sought to define a practical implementation of the retinex without particular concern for its validity as a model for human lightness and color perception. We describe the trade-off between rendition and dynamic range compression that is governed by the surround space constant. Further, unlike previous results, we find that the placement of the logarithmic function is important and produces best results when placed after the surround formation. Also unlike previous results, we find the best rendition for a "canonical" gain/offset applied after the retinex operation. Various functional forms for the retinex surround are evaluated, and a Gaussian form is found to perform better than the inverse square suggested by Land. Images that violate the gray world assumptions (implicit to this retinex) are investigated to provide insight into cases where this retinex fails to produce a good rendition.
兰道（1986）的人类视觉亮度和颜色恒常性反照模型的最新版本已经在图像处理实验中得到了实现和测试。先前的研究已经建立了兰道反照模型的数学基础，但并没有将他的亮度理论应用于广泛的图像处理实验中。我们试图在不特别关注其作为人类亮度和颜色感知模型有效性的情况下，定义反照模型的实际实现。我们描述了由环境空间常数控制的渲染和动态范围压缩之间的权衡。此外，与之前的结果不同，我们发现对数函数的位置很重要，并且在环绕形成后放置时会产生最佳结果。也与之前的结果不同，我们发现“规范”增益/偏移量在反照操作之后应用的最佳渲染。评估了反照环绕的各种功能形式，发现高斯形式比兰道建议的平方反比形式表现更好。对违反灰度世界假设的图像（这是这种反照模型隐含的）进行了调查，以深入了解这种反照模型无法产生良好渲染的情况。
