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Re: [APML] High Pass Filter technique (WAS:New TP images)

Hey Wei-Hao,

That's a good suggestion. I have plenty of images on my hard drive that
I can experiment with. For the most part, your explantions went way
over my head, but I suspect in application they may make more sense.

Thanks,
Alan

--- Wei-Hao Wang <whwang@gmail.com> wrote:
> In photoshop, maybe you can try to run a high pass filter over an 
> image to see what you get.  
> 
> Basically what happens is, photoshop (Gaussian) blurs the image 
> and subtract the blurred image from the original.  In other words,
> the 
> high pass filter does exactly the opposite thing as Gaussian blur.
> If you duplicate an image into two copies, Gaussian blur one, high 
> pass the other one (both using the same radius), and add the blurred
> and high passed image together, you will get an image identical to 
> the original one.  This tells us that any image can be subdivided
> into two components, a high passed component and a blurred component.
> 
> The simplest application of a high passed image is adding it back to
> the
> orignal.  This is identical to a 100% strength unsharp mask.  The
> whole 
> idea of unsharp mask is to change the weights of the high passed 
> component and the blurred component.  Standard photoshop unsharp
> mask increases the weight of the high passed component.  The "true 
> unsharp mask" decreases the weight of the blurred component.  Indeed,
> there is no difference between these two.
> 
> Of course, you can use the high passed images in many different ways,
> using the layer function or the apply image function.

 

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& http://www.pbase.com/avoetsch12952/fs102
& http://www.pbase.com/avoetsch12952/takpf

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