7 Replies Latest reply on Feb 23, 2008 2:52 AM by Newsgroup_User

    Removing a Moire Pattern - does it have another name?

    shampayne
      Since I changed to Fireworks from another program I lost the ability to remove a moire pattern. This is:

      "Scanning images from printed material like magazines has a very special problem ... You will discover a murky herringbone or crosshatched or dotted pattern in your scanned images from printed material, "

      Can Fireworks do this and/or has it another name. (I could be searching under the wrong name)
        • 1. Re: Removing a Moire Pattern - does it have another name?
          senocular Level 1
          I don't think Fireworks alone can do this, but I think you can find plugins that remove artifacts like this. I know I have one for greatly reducing JPEG compression artifacts. I can only assume something similar would exist as a Fireworks compatible plugin (and someone else on the boards might be able to better point you in the right direction)
          • 2. Re: Removing a Moire Pattern - does it have another name?
            Level 7
            Hi Shamp,

            > "Scanning images from printed material like magazines has a very special
            > problem ... You will discover a murky herringbone or crosshatched or
            > dotted
            > pattern in your scanned images from printed material, "


            Have you tried scanning at a high resolution (like 300 dpi or so) then
            re-sizing the image down? Works for me.

            Aloha,

            Jerry



            • 3. Re: Removing a Moire Pattern - does it have another name?
              Level 7
              On Thu, 21 Feb 2008 22:35:42 +0300, shampayne
              <webforumsuser@macromedia.com> wrote:

              > Since I changed to Fireworks from another program I lost the ability to
              > remove
              > a moire pattern. This is:
              >
              > "Scanning images from printed material like magazines has a very special
              > problem ... You will discover a murky herringbone or crosshatched or
              > dotted
              > pattern in your scanned images from printed material, "
              >
              > Can Fireworks do this and/or has it another name. (I could be
              > searching under
              > the wrong name)
              >

              Sounds like you are talking about halftone pattern, not moire. Anyway, I
              personally prefer using Fourier transform and editing frequency spectrum
              for removing it; takes a bit longer than simple filters offered by other
              software but works great. If you are Windows user, I can recommend some
              freeware for it and give some explanation.

              --
              Ilya Razmanov
              http://photoshop.msk.ru - Photoshop plug-in filters
              • 4. Re: Removing a Moire Pattern - does it have another name?
                shampayne Level 1
                Thanks to those who answered

                llya

                Yes I would be interested. Paint Shop Pro calls it "Moire Pattern Removing" which I found very useful especially when I wanted a photograph from a newspaper. At the present time I can use "Descreen" on my new printer/scanner to remove the Moire pattern for new pictures but that is no use for some of my older images.

                I'm using Windows XP
                • 5. Re: Removing a Moire Pattern - does it have another name?
                  Level 7
                  On Fri, 22 Feb 2008 22:25:31 +0300, shampayne
                  <webforumsuser@macromedia.com> wrote:

                  > Thanks to those who answered
                  >
                  > llya
                  >
                  > Yes I would be interested. Paint Shop Pro calls it "Moire Pattern
                  > Removing"
                  > which I found very useful especially when I wanted a photograph from a
                  > newspaper. At the present time I can use "Descreen" on my new
                  > printer/scanner
                  > to remove the Moire pattern for new pictures but that is no use for some
                  > of my
                  > older images.
                  >
                  > I'm using Windows XP
                  >

                  Oh yes. PSP is quite cool when it comes to bitmap editing, but can not
                  compete with FW when it comes to vectors, and vice versa.

                  Anyway, the filters in both programs are built to be "user friendly", that
                  somewhat limit their capablilies.

                  I'll try to explain the technique I personally found to be most efficient.

                  First, download the freeware "Image Analyzer" from

                  http://meesoft.logicnet.dk/

                  The key feature you need is called "Frequency domain filter".

                  Now a bit of theory on Fourier transform and frequency spectrum stuff.

                  FT is about representing the image (or other data) as a composition of
                  sine functions (sine function is periodic or "harmonic" wave). From
                  ordinary average guy's point of view, describing the photo as huge set of
                  waves added together is senseless, but scientists think different.
                  Interesting thing happen, if our image *really* have some periodic
                  component in it. Regardless of what is this component - periodic pattern
                  of printed halftone in image, or result of interaction of periodic
                  halftone with periodic nature of scanning which we know as "moire" - it
                  will give us high peak in frequency spectrum (that is, in image
                  representing how intensive are waves of dirrerent frequencies). We can
                  detect that peak and, if necessary, edit or even remove it, thus editing
                  or removing this particular signal from the image.

                  Now we go to the practical part. You should scan your images at ppi at
                  least twice as high as printing halftone screen lpi (remember of Nyquist
                  theorem). Most printings are done with lpi about 150, and newspapers often
                  at even lower values, so you should scan them at 300 ppi at least (and
                  without any software sharpening scanner may offer you). Then open image
                  with Image Analyzer. Then go to Filter -> Frequency domain filter. Now you
                  see the frequency spectrum of the image. In the dialog, you may need to
                  click "View scale" down scale a couple of times so the image is easier to
                  view. The image you see is likely to look like the galaxy of white stars
                  spreading from the top center part to the edges. The top center part is
                  brightest. Beside it, you are likely to see some additional bright stars
                  (high peaks) apart from it, forming some sort of a pattern. These are the
                  peaks representing our "parasite" periodic pattern in the image. So you
                  should just paint black over them, checking out the intermediate result
                  with "Preview" button. Important point is: don't hit the bright spot at
                  the top center area, this is useful signal. Only hit the "lone stars" far
                  from it. Once you're satisfied, hit "Ok" and save the image.

                  Althought the technique may look complicated, I often found it to be most
                  efficient when dealing with halftone or moire.

                  --
                  Ilya Razmanov
                  http://photoshop.msk.ru - Photoshop plug-in filters
                  • 6. Re: Removing a Moire Pattern - does it have another name?
                    shampayne Level 1
                    llya

                    Thanks. I've downloaded and now I'll experiment :-)
                    • 7. Re: Removing a Moire Pattern - does it have another name?
                      Level 7
                      On Sat, 23 Feb 2008 00:25:13 +0300, shampayne
                      <webforumsuser@macromedia.com> wrote:

                      > llya
                      >
                      > Thanks. I've downloaded and now I'll experiment :-)

                      It takes some time to get used to it, but using it I was able to recover a
                      couple of heavy moire scans (which I could not rescan with proper
                      resolution) for that neither PSP nor Photoshop could help, and what as to
                      removing the halftone pattern, it is still my favourite tool. Although
                      it's slow and not quite user friendly, results are much better than that I
                      can get with automated filters of other apps.

                      --
                      Ilya Razmanov
                      http://photoshop.msk.ru - Photoshop plug-in filters