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    Problems zooming out on large images

    Sometime I have to look at 1bit (B/W) very large images (4000x4000 pixel).
    These images are virtual prints from CAD tools and the graphics consist in thin lines (1 pixel wide).
    When I zoom out to show the entire image on the screen, many lines disappear (see attachment for an example):
    It seems that in zooming out the image is not down-interpolated.
    I tried to activate the "resample" option but It seems to work only in up-interpolating the image.
    Is there a solution for my problem?

    Thanks in advance,
    Simone
    Attached Files

    #2
    I suspect that a PDF would be more suitable for displaying these images.
    Before you post ... Edit your profile • IrfanView 4.62 • Windows 10 Home 19045.2486

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      #3
      I don't think you can expect a one-pixel line to remain visible under those circumstances in any medium. Even resizing an image that large with the best possible resampling filter would not preserve the lines. If it did, it would have to be especially designed for such images. One solution might be to alter a copy of the image using software such as the GIMP - select by color, enlarge the selection and fill, then resize. It would at least give a decent reduced view.
      Its: Belongs to "It"
      It's: Shortened form of "It is"
      ---------------------
      Lose: Fail to keep
      Loose: Not tight

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        #4
        I find it's quite quick to execute Image -> Resample -> x Percent -> Ok, even for viewing.

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          #5
          I find it's quite quick to execute Image -> Resample -> x Percent -> Ok, even for viewing.
          I need to zoom out and in searching for details, so resampling is not an option.
          Even resizing an image that large with the best possible resampling filter would not preserve the lines
          "Windows Picture and Fax Viewer" works well whith these images but I'd like to use a single program for all my graphic needs.

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            #6
            The only thing I can think of is to blow up the thin lines a little by using Ctrl+E\Blur. After that Ctrl+E\Find edges may improve the looks.

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              #7
              Windows Picture and Fax viewer does much better with line drawings. The attachment is a B&W map saved as in TIF format. Irfan View on the left loses a lot of detail when zoomed out to 10%. Turning on resampling doesn't help when zooming out.

              I have added this to the Feature Requests Forum
              Attached Files
              Last edited by Bhikkhu Pesala; 26.07.2007, 09:33 AM.
              Before you post ... Edit your profile • IrfanView 4.62 • Windows 10 Home 19045.2486

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                #8
                Hi Simon_owl,

                You wrote that you activated the resample function, but did you activate the right one? There are in fact two such functions: one for the window display and another one for the full screen display. Look at
                View / Display options... / Resample (free translation from french menus).
                I created a 4000*4000 one bit TIFF image with some lines 1 pixel wide and IrfanView makes a very good interpolation, even at 5%.

                Laurent
                Before you post ... fill in your OS and IV version in your profile.

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                  #9
                  I would believe that if I could see it, but I have yet to see lines that small at that zoom level as anything but random speckles no matter what the settings. I work with largee maps sometimes.
                  Its: Belongs to "It"
                  It's: Shortened form of "It is"
                  ---------------------
                  Lose: Fail to keep
                  Loose: Not tight

                  ---------------------
                  Plurals do not require apostrophes

                  Comment


                    #10
                    Originally posted by jsc37227
                    Make sure View > Display Options (Window Mode) > Use "Resample" for fitting - is checked. Also make sure in Options > Properties on the "Full Screen" tab that "Use "Resample" function for display options" is checked, but that doesn't seem to be the main control. The View menu is the one that will make the 1-bit images display properly.
                    I have made sure that the resample options are checked, but IV does not display these images at all clearly (see my previious attachment).

                    The crucial piece of information missing is that you must have "Fit Images to Window" checked too.
                    Last edited by Bhikkhu Pesala; 27.07.2007, 05:24 AM.
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                      #11
                      Hi Bhikkhu Pesala,

                      Originally posted by Bhikkhu Pesala View Post
                      The crucial piece of information missing is that you must have "Fit Images to Window" checked too.
                      You are right in noticing that there is someting else to do, but I would say rather everything except the first option (adjust the window to the image). On the other hand, one needs sometime to reload the image (Shift-R).

                      Laurent
                      Before you post ... fill in your OS and IV version in your profile.

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                        #12
                        I verified that the right settings are the "Fit image to ..." ones, while the "Fit window to image" and "Don't fit to anything" don't work.
                        Is it a bug or a feature?

                        Thanks to all for your help.

                        Simon

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                          #13
                          Originally posted by Simon_owl View Post
                          Is it a bug or a feature?
                          I think that it is a bug

                          Resampling is not used when zooming unless you have the right Display Option selected.
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                            #14
                            thing is, irfan view uses "resample" to resize the image, if it needs to resize the image to the window or your monitor, BUT IT DOESN'T use it if you simplay use the zoom tool to zoom in. i also find that pretty annoying. i often use +/- buttons in fullscreen to zoom in on a detail, beforehand the image is nice and clean and then gets pixelated. i mean, todays computers are fast enough to resample the image in high quality even if i hit the zoom tool 20 times in second...

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                              #15
                              It DOES in ‘Fit images to window’. What you mean is only possible in ACDSee Pro. But that program isn't FREE. Any other free viewer slackens zooming in on a picture, when a function like ‘Sampling’ or ‘Smooth’ or Enlargementquality is set. Maybe in future versions your wish comes true.

                              Yet I don't see the benefits of viewing a picture on a larger scale then the original. It's like looking on a newspaper fotograph with a magnifying-glass. The quality it's getting any better.

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