Removing a Line Screen

[Brian Pugh]

Hi,

I have an old photograph from a Flickr site that has a line screen

Is there any way in XnView that I can remove the screen, or
is there a plugin that can do the job?

Thanks,

Brian

[xnview]

Crop?

[Brian Pugh]

Thanks, Pierre,

Sorry, due to my first post, I think we've got the wires crossed (well I have!)

Before continuous tone images, a line screen was put on an image for it
to print. A newspaper would probably use an 85 lpi screen, maybe 100.
High quality printing (magazines, etc) would probably use something like
150 or more

The more dots, the better quality. More dots close together would result
in an area of the image being darker than a few dots

Does that help?

Brian

[XnTriq]

• The Sheridan Group: DigitalExpert » Halftones & Line Screens
• TechColor Graphics: Pre-Press Help » Line Screen
• About.com: Graphics Software Glossary » Moiré
• XnView Forum
  • Help enhancing this image?
  • Add new noise correction filter based on FFT or wavelet algo
  • Descreen for free?
  • Ximagic Denoiser Plugin
  • Effects-Noise Removal

[Brian Pugh]

XnTriq,

Many thanks for your reply and suggestions - quite a bit to go at there!

The Photoshop solution seems easy enough - I'll give it a go tonight

Thanks again,

Brian

[rra]

You might want to take a look at the program "image analyzer" from Michael Vinther
http://meesoft.logicnet.dk
It is free and it contains (next to lots of other filters) also an option to
edit an image in the fourier plane.
Stripes and regular spaced dots can easily be seen and interactively removed in this plane,
then return back to the normal plane to view the effect, save, et voila !!

I use it frequenlty to remove all sorts of screening of scanned foto-images.


René

[Brian Pugh]

Rene,

Downloaded Image Analyzer, but couldn't see how to edit an
image using the Fourier plane. Any suggestions as to how
to do this?

Thanks for your interest, anyway

Brian

[rra]

Downloaded Image Analyzer, but couldn't see how to edit an
image using the Fourier plane. Any suggestions as to how
to do this?

I admit it is a little bit hidden between other options:

go to:

/Operations/Filters/Frequency domain filter

You need a fast computer for this kind of operations !!
There are also limitations using grayscale images when using other filters.

Good luck,

René

[Brian Pugh]

Rene,

OK, saw that, but didn't know what it was!

Thanks again

[XnTriq]

• Alex Chirokov: FFT PhotoShop plugin
• 4N6site.com: Fourier Transform Plug-in
• flickr: Uncle Jerry's Photo Restoration Group » Removal of repeating patterns.
• RetouchPRO
  • Restoration Tutorials » Using the FFT filter to remove photographic paper texture by byRo
  • Forum: Discussion on byRo's tutorial
• Mark Cahill: How Automatic Deconvolution Works

[rra]

great links you gave there XnTriq,
the plugin also seems to be a lot faster.
I noticed the plugins only work with RBG images,
so one has to convert it first to RBG and afterwards back to grey.

Now if Xnview had some basic editing (in this case: erasing) features
we wouldn't have to divert to Photoshop at all

René

[XnTriq]

Well, thank you for reminding me about the Fast Fourier Transform technique, René.

Which version do you recommend?

1. http://www.alexchirokov.narod.ru/archive/fft.rar
2. http://www.alexchirokov.narod.ru/archive/Light_AdobeFilter_Release_15JAN_2004.zip
3. http://www.pages.drexel.edu/~avc25/archive/FFT_Adobe_Filter_8Apr_2005.zip
4. http://www.pages.drexel.edu/~avc25/archive/FFT_RGB_PlugIns_13April_2005.zip
5. http://home.planet.nl/~ber03728/4N6site ... fftplugin/fourier.zip

[rra]

Well actualy,

I like best the one I came up with myself: the MIcheal Vinther's implementation.

With this FFT one can seen the different spacial frequencies much clearer, and if one returns back to the original plane (iFFT), the image still is colored.
With the implementation of Chirokov the image returns grayscale, one has to use some techniques to add the colored layer back.
Disadvantage of the Michael Vinthers implementation is ofcourse the fact that you have to use hist "mage analyser" program to do the filtering,
a plugin is easier to use. .

By the way: 3 of your links (2,3 and 4) seem to be dead ?

René

[XnTriq]

By the way: 3 of your links (2,3 and 4) seem to be dead ?

I just double-checked the downloads with Firefox, Internet Explorer (browser caches cleared), and also LeechFTP.

Code: Select all

http://www.alexchirokov.narod.ru/archive/Light_AdobeFilter_Release_15JAN_2004.zip
http://web.archive.org/web/20051102154559/http://www.pages.drexel.edu/~avc25/archive/FFT_Adobe_Filter_8Apr_2005.zip
http://web.archive.org/web/20051102153400/http://www.pages.drexel.edu/~avc25/archive/FFT_RGB_PlugIns_13April_2005.zip

No problems

With this FFT one can seen the different spacial frequencies much clearer, and if one returns back to the original plane (iFFT), the image still is colored.

I must be missing something obvious here
How do I preserve the color information in Image Analyzer?

• v1.30 (2008)
  1. Operations » Transformations » Fourier transform
  2. Operations » Transformations » Inverse Fourier transform
• v1.22.3 (2005)
  1. Image » Make map » Fourier transform
  2. Map » Inverse Fourier transform

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[rra]

You have to use another option, the one I mentioned in a previous message:

/Operations/Filters/Frequency domain filter.

You edit with a brush-eraser with selectable size, once done, hit OK ; that's all there is to it .
I am not sure about older versions, but this one is available for version 1.30 .
By the way: links 3 & 4 are still dead, link2 does seem to work, strange indeed .

René