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High Pass Filter

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high-pass.scm6.15 KB

A general purpose high-pass filter plugin. It shows up as Filters->Generic->High Pass Filter. You can select a blur radius that sets the size of detail to be passed by the filter, as well as an option to keep the source layer or replace it.

EDIT: Updated to use grain extract rather than the previous method, This looses less histogram data and is closer to the Photoshop version...

It actually implements 5 different high pass modes:

  1. Colour - I think this is the same as photoshop's high pass filter effect.
  2. Preserve DC - like colour, but adds the average image colour back in.
  3. Greyscale - this desaturates the layer before high pass filtering.
  4. Greyscale, Apply Chroma - as above, but blends it in with the source layer colours
  5. Redrobes - (named after the technique described by Redrobes)

They are all straightforward, using a basic "duplicate, blur, grain extract, merge down" process, with a few small details added for each, except the Redrobes mode. The steps he described were:

Get an image 1.
Blur it quite a lot 2.
Blur it until its a constant colour 3.
Use Image arithmetic to generate 2 - 3 => 4
Use Image arithmetic to generate 3 - 2 => 5
Take 1 and subtract 4 and add 5 => 6

While this is supposed to be the same as a basic filter with preserve DC offset, it seems to give slightly different results, so I left it in :)

For more details and sample images, see my blog post:
http://www.silent9.com/blog/archives/152-High-Pass-Filter-Plugin.html

Code License: 
GIMP Version: 
Scripting Engine: 

Comments

hey all user,
You also discus here right and I read the High Pass Filter carefully.
I wanna learn more about this.
anyone tell me where can I found more tips about this.

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Yeah, I'm with the lost person. I'm lost too; everytime I click the high-pass.scm thing, no download or even save comes up. Help?

I am not a computer person, but I use gimp for my photography and I reeeeeeeeeeally don't understand how to download this filter...or script-fu... or whatever it is! Help?

Download high-pass.scm and put it in your scripts folder. On my computer its C:\Program Files\GIMP-2.0\share\gimp\2.0\scripts. You'll probably see a lot of other .scm files in there. To use it, just select it from the menu: Image window -> Filters -> Generic -> High Pass Filter. No complex assembly required. :)

Thanks for this plugin. Now we can do that sharpen thing of photoshop with the high pass :P.

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