Using the FFT Filter to Remove Photographic Paper Texture

Please download to get full document.

View again

of 3
28 views
All materials on our website are shared by users. If you have any questions about copyright issues, please report us to resolve them. We are always happy to assist you.

Download

Document Related
Document Description
The FFT (Fast Fourier Transform) technique offers a way to remove (most of) the texture, leaving us with a photograph that can now be easily retouched.
Document Share
Document Tags
Document Transcript
  Using the FFT filter to remove photographic paper texture The FFT (Fast Fourier Transform) technique offers a way to remove (most of) the texture, leaving us with a photograph that can now be easily retouched.Heres a before ! after image to show what were tal ing about#.$n the left we have an image ( thank you, FrannyMae ) scanned (*1)  from a photograph on embossed paper % on the right the result after applying the technique described here.&ome observations'The FFT technique... ...has eliminated the superimposed embossed texture ...has preserved the underlying features ...has $T removed spots and random noise ...has $T fixed any colour blotches.*hat is FFT+*ithout going into too many gory details, FFT is a mathematical transformation that ta es a normal- image (that we can understand) and transforms it into an alternative mathematical- image (that only a computer understands).*hat is the FFT technique+sing the mathematical- image we can easily identify and eliminate the repetitive texture. *hen we transform bac (called, /nverse FFT) to the normal- image, the texture has been removed.0reparation1ou will (of course) need an FFT filter. There are some options (*2)  available, but the filter that has been most widely adopted is the version by 2lex 3hira ov. (*3 download and installation) .The method described here is for this filter but, with some minor adaptations, can be applied to all other FFT implementations. How to appl the FFT techni!ue 4) 5uplicate srcinal image6 7ight clic on title bar6 5uplicate ( merged, if it has more than one layer  ) to a new image.8) Flatten all 9ayers1ou may not need this but, for precaution, flatten all the layers...: alt ;: # ;, : F ;. This is because FFT doesnt understand layers, mas s, alpha channels etc. The image must be <ust one =ac ground- layer and nothing else>) 7un Filter;Fourier Transform;FFT 7?=  1ou should be loo ing at something li e this#(dont worry@)A) &elect <ust the 7ed 3hannelB ?o to the channels paletteB &elect the 7ed channel only (or turn off the ?reen!=lue)B 1ou now have something li e this (don$t worr%%) 5o you see the little stars+ These small white points correspond to the texture that is superimposed on the  photo. 2ll the rest, especially the central part, is the image that we want to preserve.C) 0aint out stars in the 7ed 3hannel6 sing a soft brush paint the stars out with a dar grey or blac . .6 &' 'T T'UH TH T+,# -T,+  6 1ou should have something li e this.. (don$t worr%%%) D) &elect all channels again6 $n the channels palette turn bac on the green and blue channel (easy to forget this bit) 6 /f necessary, flatten the layers (: ,lt ;: # ;: F ;)E) 5o the /nverse Fourier Transform6 7un Filter;Fourier Transform; . FFT 7?=6 *hat no colours+ Thats right@ The FFT wor s only on the luminosity (  greyscale ) information.) 0ut the colours bac in'6 &lide, with : -hift ; pressed ( to align ), your ( now un-textured  ) luminosity bac layer on top of the srcinal ( that’s the one we left behind in step 1 )6 &et this new layerGs blending mode to 9uminosity.6 &elect your srcinal layer, which is below the new 9uminosity layer6 2pply a small radius (8 or > should do) oise ; /edian  filter ( this blurs the colours a little, but dont worry all the important sharpness is in the luminosity layer  ).2nd here we are...  Thats all fol s@
Search Related
Similar documents
View more...
We Need Your Support
Thank you for visiting our website and your interest in our free products and services. We are nonprofit website to share and download documents. To the running of this website, we need your help to support us.

Thanks to everyone for your continued support.

No, Thanks
SAVE OUR EARTH

We need your sign to support Project to invent "SMART AND CONTROLLABLE REFLECTIVE BALLOONS" to cover the Sun and Save Our Earth.

More details...

Sign Now!

We are very appreciated for your Prompt Action!

x