照明不变图像 [英] Illumination invariant image

问题描述

我尝试使用openCV创建一个照明不变图像，如本文所示： http：// www .cvc.uab.es / adas / publications / alvarez_2008.pdf

有人知道如何从日志图中创建图像在OpenCV中？

解决方案

据我所了解的两篇文章，他们是从一个假的前提开始，方法从2D获得1D照明不变信息（例如来自Luv的uv，来自HSV的HS等）色彩空间。他们说照明不变，但它们显示一种方法从颜色对的对数比例，例如{log（R / G），log（B / G）}获得色温不变信息。你可以想象设置，在一个调光器上的灯，他们绘制的颜色比率：调暗灯光，是的，照明的变化，但色温T也是如此。

更不要说光不是所有的黑体色温朗伯。这个方法在世界上如何工作？但他们的结果看起来不错。

所以，对有趣的方法：最大熵

如上面的答案，投射（log of）uv空间到一个向量角度theta。 theta应该是什么？搜索theta以最大化结果的熵。也就是说，得到1D结果中最清晰的峰。类似自动对焦的类型。

为了回答你的问题，在opencv中使用calcHist。在计算日志后，当然。

I try to create an illumination invariant image with openCV like in this paper here: http://www.cvc.uab.es/adas/publications/alvarez_2008.pdf

Has someone an idea how one can create that image from the log-log plot image in OpenCV?

解决方案

As far as I can understand the two papers, they are proceeding from a false premise and arriving at an interesting method for getting 1D illumination invariant information from 2D (such as uv from Luv, HS from HSV, etc) color space.

They say illumination invariant, but they show a method of obtaining Color Temperature invariant information from log ratio of color pairs, say {log(R/G),log(B/G)}. You can imagine the setup, with a lamp on a dimmer, and they plot the color ratios: dim the lights, yes, the illumination changes, but so does the color temperature T.

Not to mention that light is not all blackbody color temperature Lambertian. How in the world can this method work? But their results look good.

So, on to the interesting method: Maximum Entropy
As in answer above, project the (log of) uv space onto a vector at angle theta. What should theta be? Search theta to maximize entropy of the result. That is, to get the sharpest peaks in the 1D result. Sort of like an auto-focus.

To answer your question though, use calcHist in opencv. After computing the log, of course.

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