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FFT and Golf Balls

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  • FFT and Golf Balls

    This photograph is a small part of a long panoramic group photo.
    It has been scanned following all the suggestions / tutorials on this site and this is the best I can get.

    I am not asking for anyone to restore this but I hope to get some suggestions on the golf ball texture.

    I think Neat image blurs this picture to much.

    FFT which has always worked well for me in the past has let me down with this picture
    When I run FFT I can get rid of the grain but I am left with lines on the print which is just as bad.

    I suppose my question is
    Does anyone understand the Stars that FFT gives? I usually remove all except the big one. Is there perhaps a way of removing some of the stars to avoid getting lines on the picture? When I remove just the 4 stars nearest the big star I seem to get the best results from this picture.

    This picture clearly needs some Level / Colour / Sharpen adjustment but this also improves the golf balls so I’ve posted the best original scan.

    I did complete this image by eliminating every golf ball on the face with the Clone Stamp and my friend is happy with the finished picture. I’m just hoping to find some suggestions for an easier way next time.
    Attached Files
    Last edited by Cameraken; 05-24-2005, 10:57 AM.

  • #2
    Did you scan this, or was it given to you as is.

    If you have the original to scan, try scanning once, then rotate image by 180 degrees and scan again.

    In photoshop, copy both scans to seperate layers.
    Set blend mode of top layer to either lighten, or darken (whichever gives best results). Because the shadows caused by the bumps are different, due to the change in scanned lighting, they cancel out, and the bumps should be less noticeable.

    Hope this helps a little.


    • #3
      Hi Cameraken,

      Welcome to RP!

      The result I got with FFT was acceptable ... It is a bit more blurred than I expected but the resolution of the image posted is very, very low ....
      Attached Files


      • #4
        Gary this is scanned from about ¼ inch of the original print. I followed all the tutorials about rotating the image and setting blend modes etc.
        This image is already a combination of that process.

        You have done a wonderful job.
        I had to increase the jpg compression to get the file uploaded to retouch pro (100kb max)
        I tried again on the compressed file and I still don’t get the results you have.
        I am still getting lines across the image.
        See attached image

        If anyone reading this is interested I will move this to a ‘Reverse Tutorial’
        As it seems that only a few people here understand it (Duv, Flora,Byro)
        Can someone can please tell me where to post it?

        The best information I found was here
        But following this still does not give me the results Flora got.

        I think this texture removal is really important to making good images as many old photographs have texture.

        FFT has worked OK for me in the past and I can’t understand why I am having problems this time
        Attached Files


        • #5
          You might have some success trying the following:
          Make 3 copies of your picture. Adjust levels.
          On the first, select a small portion of the pic and clean it up by cloning out the balls. Go to Filter:Pattern Maker and click on Generate. Save the pattern with the button at the bottom. Cancel out of Pattern Maker. Go to Healing Brush and set it to pattern. Pick out the one you created and heal out the balls.

          On second copy, run FFT. You should end up with a B/W image. Shift drag onto Healed image, change to Luminosity and change opacity to suit. High Pass sharpen and fade back in Soft Light.

          Attached Files


          • #6

            Since I sell FFT code, Doug gave me a head's-up on this. The UI for my software is completely INAPPROPRIATE for photography or people that don't want to know about FFTs, and a separate discussion will need to be held over what you'd like for tools (since I'm a plugin writer).

            In any case, here's what I was able to do with removing the pattern noise from the Power Spectrum manually (attachment).

            I have not attempted to go after the random noise in the image and there is evidence of the top layer of the photograph flaking off and yellowing in the blue channel.

            This should give you an indication of what's possible.

            -Chris Russ

            P.S. there is a 3-week demo of the FoveaPro software available if anyone wants to play with it. I do NOT expect any of you guys to buy it -- you're not the intended audience. If anyone is interested in playing I'll be happy to provide a URL for download.
            Attached Files


            • #7
              tutorial on FFT PowerSpectrum

              And, I suppose I could write up a discussion on what you're actually seeing when you look at a PowerSpectrum (the "FFT Stars" that someone was referring to, above).

              Gluttons for punishment.


              • #8
                Thanks for the info Chris. Personally, I'd like to play with the FoveaPro if you could provide the URL.

                Also, do you have any tips on how much of a star to remove. What I mean is that often, horizontal and vertical lines emanate out from the centre of the star, sometimes for quite a distance. Is it recommended just to remove the centre star or should we be cloning out the lines as well? Or is it, try it and see what happens?



                • #9
                  About FFTs

                  Demo for FoveaPro can be downloaded from:

                  Mac Version
                  PC Version

                  (Runs for 3 weeks.)

                  There is a tutorial on using it for Fourier processing at:

                  Chapter 4 - Processing in Frequency Space

                  But rather than make this a blatant ad for a product that was designed for a different group of people than y'all, let me instead talk about reading Fourier transforms and some of the things you can look for in them.

                  #1 - The Fourier Transform. We convert an image (no loss of data) into a summation of sine waves. Each possible sine wave has a strength and those are plotted in the Power Spectrum. This is a map of the direction of the different sine waves and their period/phase -- longer sine waves are in the center of the plot (DC is the center and represents the mean value of the image) with shorter sine waves around the outside.

                  The center cross-shaped radial lines are a combination of the extra frequencies that it takes to wrap around from the left side of the image to the right side of the image (vertical part) and the top side to the bottom side of the image (horizontal part).

                  Here is an example Power Spectrum:


                  In it you can see the center cross (caused by the edges of the image not matching each other) and a spike in the center which corresponds to the overall image brightness and the gross gradient in the image. As we come out further from the center, the amount of power starts to back off. (This plot shows power as black so the "background" will tend to lighten as we come further out radially from the center.)

                  You will also notice a number of other spikes. These are caused by a halftone pattern in the original picture:


                  If we create a mask to eliminate just those spikes and apply it to the Power Spectrum (like this one):


                  We get the following result:


                  Actually, to get a very good result, and to blur the image some, we also apply a low-pass filter (in this case a Butterworth) and make the Power Spectrum look like this:


                  Notice that it now lightens up a lot toward the outside edges and there are holes where the spikes used to be.

                  Here is the result image:


                  That low-pass filter actually filled in the gaps in the original halftone dots. There are a host of other filters that can be done, but this should give you a small idea of what's possible.

                  It turns out that you can do very high speed convolution in this mathematical space (especially with large filters), remove pattern noise, make some measurements for periodic shapes, determine the real vs. empty resolution of an image, construct really interesting filters (like this one), and otherwise confuse people.


                  P.S. When I was a college student in the early 80's we were challenged to perform a periodic noise removal problem. At that time (less politically correct than today) Cheryl Teigs had posed in a fishnet bathing suit that left little to the imagination. Since that suit was fishnet, and thus periodic, we were challenged to remove the suit. (Obviously there were no women in the class.) Needless to say, the technique works.


                  • #10
                    Followup for Duv

                    You asked whick parts of the "FFT Star" or the cross to remove. I would say NONE. That cross represents the frequencies that it takes to do the step from the top to the bottom and the left to the right -- if you remove it, you'll mess up your image up significantly.

                    Now, if there is a spike sitting on top of the cross, you can remove THAT. And, lines that are not at the 12, 3, 6, and 9 o'clock positions that do not run through the center of your image you can safely remove.

                    Other stuff might be problemmatic. Perhaps you should post an image and we'll deconstruct it.

                    Also, let's start with b&w. Color information can be different in the three channels, so lets deal with one channel at a time.


                    • #11
                      Median + Neat Image

                      Well I ran the median filter at 3 then Neat Image on the picture.
                      Attached Files


                      • #12
                        I couldn't let another FFT thread pass by without sticking my nose in....

                        Originally posted by Cameraken
                        FFT which has always worked well for me in the past has let me down with this picture ...... FFT has worked OK for me in the past and I can’t understand why I am having problems this time
                        FFT is a mathematical process - as you can see by jcr6's post. It is great for detecting well-defined repetitive frequencies in an image.

                        To our eyes the "golf balls" seem to be exactly repetitive and using FFT you will be able to remove all the repeating frequencies. What you have got left after that is noise that was superimposed on those frequencies.

                        Although we can see some sort of pattern in this noise, it doesn't repeat any more - there are some white dots, then a few black ones......

                        Why is this one different? Because other paper textures are usually less embossed than this one and don't pick up so much dirt (=noise).

                        Originally posted by Cameraken
                        The best information I found was here
                        I left a note there advising that there is an easier version available now which doesn't need the HSB stuff.

                        For those (few, OK) mathematically inclined.. there is actually a way to calculate where the stars will be in the FFT. Something like.. measure the pixel distance between the texture ridges, divide the total image dimension by this number, then count out from the centre. I did have it figured out once and it did work.

                        (Yeah, I know - 1.496Km to go)


                        • #13

                          Can you come up with a report on the FoveaPro at some point. Something for non-numbers people to appreciate? Ro?



                          • #14
                            OK, I'm on it
                            But it's a 22MB download - so only tomorrow.


                            • #15
                              Repeat: Fovea wasn't intended for you guys

                              I never intended for this to be an ad for Fovea -- it is a general purpose image analysis system for scientific imaging.

                              Now, some of the things in there (like the Fourier suite) *might* make an interesting product at a more acceptable price, but I need to see what you guys want/need/are willing to learn.

                              My basic inclination is to completely hide the FFT under-the-hood, whether for deconvolution (Optipix->Refocus), using an ideal inverse (a very neat tool for image enhancement), halftone removal, etc.

                              The learning curve, for one, is huge. Two, the Fourier suite works in b&w. Three, there are 177 plugins in Fovea. Four, the "tutorial" is 500 pages.

                              Then, again, it might be interesting to see how he feels after going through it. <evil laughter>