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小木虫论坛-学术科研互动平台 » 专业学科区 » 数学 » 计算数学 » 图像的非线性扩散滤波倒是是怎么扩散的？
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xiashaoyan

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[求助] 图像的非线性扩散滤波倒是是怎么扩散的？已有1人参与

近一直看图像的非线性扩散，有一个问题一直困扰的自己，问题是：图像的非线性扩散滤波倒是是怎么扩散的？
问题1：在各向异性扩散的PM模型中，通常边缘处的扩散系数比较小，而噪声处的扩散系数比较大，那么通过这样的设计，假设在噪声点(这个噪声点灰度值比较大)附近有边缘信息，那么经过扩散后，这个噪声会的灰度值降低了，那么降低的灰度值量是不是加到附近边缘信息的灰度上量，也就是，在扩散过程中，扩散是相邻两个点灰度值量的扩散吗？或者说，噪声点经过扩散后，扩散的量加到附近点上了吗？我看过一篇文献，说传统的PM扩散是一个绝热过程，只在相邻两个点之间进行扩散。问题2：如果正如我看到的文献所说的那样，一般的PM扩散是两个点的扩散，那么岂不是会改变一些边缘信息的灰度值吗？(因为相邻扩散的两个点是相互影响的)
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1楼2015-09-26 17:39:05
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zaq123321

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xiashaoyan: 金币+5, ★有帮助 2015-09-27 23:08:19
It's an iteration. You need to decide how many steps you want to go. Thus to design a good stop criterion is not easy. Usually the iteration steps and step size should be reported in paper. How can you say just diffusion within two points. One image is 128x128 or 64x64

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2楼2015-09-27 00:39:56
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feixiaolin

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3楼2015-09-27 06:52:49
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xiashaoyan

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2楼: Originally posted by zaq123321 at 2015-09-27 00:39:56
It's an iteration. You need to decide how many steps you want to go. Thus to design a good stop criterion is not easy. Usually the iteration steps and step size should be reported in paper. How can y ...

I think the iteration steps and step size of every point in a image is same,so it is hard that this design is keep all point have a good a diffusion.And my quesion is  that what is diffusion for PM model or AD diffusion?Because I read a paper said that:AD model  considers relations only between neighborhoods, rather than among neighborhoods; therefore, the thermal diffusivity is independently calculated between a center node and each neighborhood.,but I don't undarstand this meaning,and now I think how diffusion process for a image,especially for a noise point and signal point.Finally, if you interest this quesions, you can add my qq：1403291906，or you can left you email/QQ,I very expect that I can interact with you,Thank you!
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4楼2015-09-27 23:23:38
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zaq123321

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what is diffusion for PM model or AD diffusion?
I think PM model is a diffusion model. What's AD diffusion?

AD model  considers relations only between neighborhoods, rather than among neighborhoods
My guess is that: Just use 5 points discretization or 9 points discretization for a point, or 13 points?

the thermal diffusivity is independently calculated between a center node and each neighborhood
My guess is that: For the center node, after you calculated and get a new value, whether you want to use this new value to update next pixel value or not? If using the new calculated value, then it's not independent. If using the value before updated, it's independent.

I think how diffusion process for a image,especially for a noise point and signal point.
Diffusion process doesn't know what's signal, what's noise. You need to figure out what's the difference between signal and noise and get their characteristic and put them in the diffusion model. That's the idea. So for isotropic model, it smoothes equally for noise and signal. For anisotropic model, it treats edges etc as features or signals and tries to preserve them and do less smooth. For other parts treat as noises and do harsh smooth.
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5楼2015-09-28 00:24:17
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