生物谷报道:我们能够很容易分辨出一件东西是用白蜡做成的还是用石膏做成的,也能够很容易分辨出一个木质表面是否进行了抛光处理,只要观察表面是亮还是暗、是否光滑就可以了。这便涉及到一个先有鸡还是先有蛋的问题。为了推断一个三维表面的反光质量,我们需要关于形状和照明情况的详细信息,但要推断其中的每个因素,又需要关于其他因素的知识。Motoyoshi等人发表在5月10日《自然》杂志的最新研究解开了这个谜。在此过程中,他们给出了一些对机器人视觉系统的开发人员和创造虚拟现实的计算机动画制作人员可能会很有用的线索。关键是一个简单的图像统计原理:我们对光亮程度的感觉是由一个图像中亮度值分布的正偏(positive skew)量决定的。
FIGURE 2. Perceived lightness and glossiness may be based on the skewness of the luminance histograms.
a, The stucco-like surface on the right looks darker and glossier than one on the left even though the mean luminance of both images is equal. We note that the luminance histogram is negatively skewed for the left image (skewness = -1.34), and positively skewed (skewness = 2.40) for the right image. b, In the left panel, as the diffuse reflectance increases, the lightness ratings given by human observers increase (red circles, y-axis scale on the left side) and the skewness of the image histogram decreases (black circles, y-axis scale on the right side). The data were obtained with medium-glossy surfaces. In the right panel, we see that as the specular reflectance increases, both the rated glossiness (red circles) and the histogram skewness (black circles) increase. The data were obtained with dark-grey surfaces. c, The rated lightness (left panel) and glossiness (right panel) of the 63 surface images of varying diffuse and specular reflectance under different illumination conditions. The human ratings correlate well with the skewness of the image histogram. Error bars represent 1 s.e.m across six observers. d, The effect of histogram manipulation on perceived lightness and glossiness. For images of stucco, crumpled paper, and fabric, the luminance histogram was matched to a positively or negatively skewed beta distribution. The rated lightness (left panel) and glossiness (right panel) varied according to the final skewness of the manipulated image (mean = 8.2 cd m-2, s.d./mean = 0.1, See Supplementary Data B for data obtained with other parameters). Error bars represent 1 s.e.m. across seven observers.
原文出处:
Nature Volume 447 Number 7141
Image statistics and the perception of surface qualities p206
Isamu Motoyoshi, Shin'ya Nishida, Lavanya Sharan & Edward H. Adelson
doi:10.1038/nature05724
First paragraph | Full Text | PDF (1,022K) | Supplementary information
See also: Editor's summary | News and Views by Landy
作者简介:
Edward H. Adelson
Professor of Vision Science
Dept. of Brain and Cognitive Sciences
Massachusetts Institute of Technology
Web: http://web.mit.edu/persci/people/adelson
Secondary Office:
Computer Science and Artificial Intelligence Laboratory (CSAIL)
My lab is part of the Perceptual Science Group in the Department of Brain and Cognitive Sciences at MIT, and focuses on topics in human and machine vision, including mid-level vision, material perception, image statistics, and motion analysis.
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