Using the FFT filter to remove photgraphic paper texture

[Flora]

Originally Posted by deadants

I'm using a mac as well and have googled all over looking for a plugin. So far no luck.

I have borrowed my brothers PC laptop and installed the filters, I tried the FFT RGB and imeadiatly did the IFFT RGB but the image came out transparent. Any suggestions?

Hi deadants,

what I think happened is that you run FFT on a Layer instead of a flattend image ...

[deadants]

No I definatly had only one Layer. I even did step 1, duplicate the image. It's a strage one

[byRo]

IFFT is real choosy and doesn't respond to anything but the most basic of images. Besides not allowing layers, you also cannot have any masking or alpha channels and your (one) layer must be "Background" (Flatten the layer <alt><L><F>).

If this doesn't help, another tip is to keep checking the IFFT from time to time instead of waiting till the end. If it's OK then just undo (<ctrl><z>) and continue fixing the FFT image.

Hope this helps,

Rô

[Cameraken]

Hi Wils and deadants

There IS a mac version.
It’s called ImageJ

Image J is part of The Image Processing Toolkit
Available Here for Free
http://rsb.info.nih.gov/ij/download.html
ImageJ runs on Linux, Mac OS 9, Mac OS X and Windows
The Docs are here
http://rsb.info.nih.gov/ij/docs/
And the bit about FFT is here
http://rsb.info.nih.gov/ij/docs/menus/process.html#fft

It is Not a plugin but a complete program. You will need Java Installed.

Deadants
I have also had a similar problem with the image going transparent. I found it was because I went too close to the cross and the centre star. Do as Byro suggests and keep going back to check your results and saving them.


Ken

[deadants]

Hi Guys,
I did all of the suggested steps but it just kept going transparent, so what I did was create a new background layer and filled with black, then placed the transparent layer over it. That seems to have solved the problem.

I have tried imajeJ but It works a bit differently I found after much trial and error that you have to completely erase the centre star. I wonder if someone else with a Mac could confirm what I'm doing. You can see the attached image has on the left the original halftone image, the centre is the FFT and the right is the IFFT. I know it doesn't look to good but if I erase the outer stars and leave the centre star untouched the image turns black.

[Cameraken]

Hi deadants

I have ImageJ installed and I can probably help but this is probably not the correct thread to do this in.

You can start a new thread in the help section or We can continue in the thread that started this tutorial Here

http://www.retouchpro.com/forums/image-help/10660-fft-golf-balls.html


Ken

[deadants]

OK Ken, New thread coming up.

[june`]

I am scanning fine art pictures and have tried this tut. I am still picking up the canvas texture from the picture I have scanned. Is there any way to remedy this?

Thanks,

June

[Cameraken]

Hi June. Welcome to RetouchPro.

FFT works on a uniform pattern of texture. If you are working on canvas originals then the canvas may be stretched and then the pattern is no longer uniform

If this is the case then you could try splitting your picture into sections and using FFT on each section.

If your fine art pictures are not on canvas then post your results and we will try to help.

Ken

[june`]

i am trying to use this filter. At step two, the entire image goes black?

Any help will be appreciated.

Thanks,

[Cameraken]

Hi June.

2) Flatten all Layers
You may not need this but, for precaution, flatten all the layers...<alt><L>, <F>. This is because FFT doesn’t understand layers, masks, alpha channels etc. The image must be just one “Background” layer and nothing else;

Byro included this step to make sure you only have one layer as FFT will not work on Layers. This should not make your image black
Try using the mouse instead of the shortcut. Layer > Flatten Image.
If Flatten Image is greyed out then skip this step and move to step3

Ken

[june`]

I checked that. Tell me, is there a limitation on the size of the file the filter will work on?

Thanks again,

June

[Cameraken]

There is nothing in the code to limit file size. However I suspect that FFT could be memory intensive so file size will be limited by your computers memory and disk space.

This will not affect the quality of the results. It will just slow down the conversion.

Ken

[ebbtide]

Hi,
WOW what a great time saver, thanks Ro. One question. 99% of my work has been on gray images so I'm not familiar with a lot of the color operations. In trying an RGB and getting to your Step 8 (Put the colours back in) you state "Slide, with ......". My question is Slide what? Where does this luminosity layer come from? Its not listed in the channels or layer list.

Thanks for bearing with my ignorance, ebbtide

[byRo]

Glad you found this useful.

The FFT process works only on the luminosity (greyscale) of the image.
So, what we want to do in this step is to mix the colour information of the original with our "clean" luminosity.

This could be done by copying (<ctrl><C>) the new luminosity image and pasting (<ctrl><V>) on top of the original.

The "slide" method is just a short-cut. Details......

- You need to have the "luminosity" image active, but also have visible some part of the original image.
- On the layers palette, select the layer of the "luminosity" image.
- You can now drag this layer from the layers palette onto the visible part of the original image.
- Now you have a new luminosity (greyscale) layer on top of the old colour information.

Only it will be in the wrong place! Which is why you'll remember to press <Shift> while dragging, which aligns the layer correctly.

Yeah, I know - the short-cut looks longer than the original. On paper, yes. In practice, no.

Rô