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Re: [PanoToolsNG] incompletely uploaded jpeg and tiff in FTP - how to detect?

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  • Mihai Stanescu
    If you can run programs then make a small program to read the header of the image and see its length
    Message 1 of 4 , May 1, 2009
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      If you can run programs then make a small program to read the header
      of the image and see its length



      On Thu, Apr 30, 2009 at 11:43 AM, Jeffrey Martin <360cities@...> wrote:
      >
      >
      > We're trying to set up an FTP uploading system for images.
      >
      > The big issue so far is, how to tell if a file has been completely uploaded.
      >
      > For ZIP files, we've solved it.
      >
      > Is there a simple way to tell if a JPEG or TIFF file is completely uploaded
      > or not?
      >
      > [Non-text portions of this message have been removed]
      >
      >
    • Roger Howard
      Yeah, there are a number of ways, depending on the upload process - 1. If you control the uploader tool (probably don t) then you can calculate a checksum and
      Message 2 of 4 , May 1, 2009
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        Yeah, there are a number of ways, depending on the upload process -

        1. If you control the uploader tool (probably don't) then you can calculate
        a checksum and compare to the uploaded file's checksum... or even just a
        filesize compare
        2. Use one of a number of tools that will check the consistency of the
        formatting - this won't necessarily prove the upload was incomplete... it
        could have been damaged prior to upload - but is a good idea any time
        you're accepting media files anyway.

        Some ideas:

        exiftool - though not built for this, it's pretty good about error
        reporting
        libjpeg and libtiff both have a variety of tools which will report errors
        on parsing those formats - likewise, many tools based on these libraries
        (for instance, ImageMagick) will report errors back up to the user based on
        parsing problems encountered in the library
        jhove - a much more robust/complex tool, but designed for
        validating/profiling a wide range of file formats

        3. If you want something really simple:

        for jpeg: check that the file ends with "FFD9" (in hex) - the only time
        that sequence should appear in a JPEG is at the very end
        for tiff: check that the file ends with "0000" (in hex) - it's not an "end
        of file" marker technically, but, I believe, all TIFFs should end with it
        IIRC; of course it's quite possible for a TIFF to contain "0000" elsewhere
        in the file, so this isn't a guarantee - but if the file DOESN'T end with
        0000 you can be sure it's incomplete.
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