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What does changing DPI (on Resize/Resample) actually do?

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    What does changing DPI (on Resize/Resample) actually do?

    If I open a PDF and select Image/resize|resample from the menu and only change the dpi (eg from 96 to 300dpi) and then save a a jpg the saved file appears to be identical (same size & dimensions) although the meta data (in Windows file properties) does show 300 for the DPI.

    Is this correct?

    As far as i can tell, DPI is a meaningless attribute for the digital display of images but I can see how it matters for physical printing.

    I'm interested in this as I need to occasionally generate 300dpi images for journals for publication (e.g. graphs & charts ).

    Is DPI ever relevant other than when physically printing hardcopy?

    Thanks
    John

    #2
    In Settings, Plugins, PDF Plugin options, you can change the DPI used to render PDF files on opening them.

    It is also relevant when placing images in page layout applications.



    Yes, for displaying images on web pages, DPI is meaningless, and misleading. It is just the number of pixels that determines how good the detail is.

    See Digital Image File Types for a more detailed discussion.
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    Last edited by Bhikkhu Pesala; 09.04.2017, 03:50 PM.
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      #3
      Originally posted by Bhikkhu Pesala View Post
      In Settings, Plugins, PDF Plugin options, you can change the DPI used to render PDF files on opening them.
      Thanks so much - that was the missing piece in the jigsaw that I needed and now resize/resample and file.save-as jpg has the desired effect of generating a higher quality image with increased DPI

      for future readers, with my version (4.42) the exact menu setting was:
      Options:: Properties/Settings :: Select Plugins in left-hand list :: ‘PDF Options button :: In loading options, select Use(new).. and ‘set DPI’ change from 96 to 300 (or as desired)

      Thanks also for the helpful link.

      John

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