Modify Jpeg via BinaryWriter renders "useless" output

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  • Richard Coltrane
    #1

    Modify Jpeg via BinaryWriter renders "useless" output

    Hello,

    If i take a jpeg and pipe it from a binary reader to a binary writer,
    everything is fine and I can still use it.
    If i take that same jpeg and piping code and simply add a byte encoded
    string to the front of the file then I can no longer open it in an image
    editor. This i would expect.

    However if i open that image in notebook and remove the string I entered,
    then i still cant open the file in an image editor, does anyone know why
    this is?? Once ive removed the 4 character string with notepad the files are
    "seemingly" exactly the same?? They have precisely the same file size (down
    to the byte) and the bytes within the file are also exactly the same??

    Whats different?

    Thanks



    Tags: None
    • =?Utf-8?B?UGV0ZXIgQnJvbWJlcmcgW0MjIE1WUF0=?=
      #2
      RE: Modify Jpeg via BinaryWriter renders "useless&q uot; output

      If your goal is to embed messages into images, you want to look into
      steganography. Corinna Johns has a series of articles on codeproject.com on
      the subject.
      -- Peter
      Site: http://www.eggheadcafe.com
      UnBlog: htp://petesbloggerama .blogspot.com
      Short Urls & more: http://ittyurl.net


      "Richard Coltrane" wrote:
      Hello,
      >
      If i take a jpeg and pipe it from a binary reader to a binary writer,
      everything is fine and I can still use it.
      If i take that same jpeg and piping code and simply add a byte encoded
      string to the front of the file then I can no longer open it in an image
      editor. This i would expect.
      >
      However if i open that image in notebook and remove the string I entered,
      then i still cant open the file in an image editor, does anyone know why
      this is?? Once ive removed the 4 character string with notepad the files are
      "seemingly" exactly the same?? They have precisely the same file size (down
      to the byte) and the bytes within the file are also exactly the same??
      >
      Whats different?
      >
      Thanks
      >
      >
      >
      >

        Comment

        • Hans Kesting
          #3
          Re: Modify Jpeg via BinaryWriter renders "useless&q uot; output

          Richard Coltrane formulated on zondag :
          Hello,
          >
          If i take a jpeg and pipe it from a binary reader to a binary writer,
          everything is fine and I can still use it.
          If i take that same jpeg and piping code and simply add a byte encoded string
          to the front of the file then I can no longer open it in an image editor.
          This i would expect.
          >
          However if i open that image in notebook and remove the string I entered,
          then i still cant open the file in an image editor, does anyone know why this
          is?? Once ive removed the 4 character string with notepad the files are
          "seemingly" exactly the same?? They have precisely the same file size (down
          to the byte) and the bytes within the file are also exactly the same??
          >
          Whats different?
          >
          Thanks
          Try using your own process in reverse: use a .Net program to strip
          those first bytes and leave the rest of the data intact.
          I suspect that that *will* work (see the other replies)

          Hans Kesting


            Comment

            • Richard Coltrane
              #4
              Re: Modify Jpeg via BinaryWriter renders "useless&q uot; output

              Hi Peter,

              no it wasn't but thanks for the response, ive always wonderd what that was
              called. Spies and school kids use that stuff right?


              "Peter Bromberg [C# MVP]" <pbromberg@yaho o.NoSpamMaam.co mwrote in message
              news:B003760B-3A66-4FC4-A5A6-1CC22D2A7B2C@mi crosoft.com...
              If your goal is to embed messages into images, you want to look into
              steganography. Corinna Johns has a series of articles on codeproject.com
              on
              the subject.
              -- Peter
              Site: http://www.eggheadcafe.com
              UnBlog: htp://petesbloggerama .blogspot.com
              Short Urls & more: http://ittyurl.net
              >
              >
              "Richard Coltrane" wrote:
              >
              >Hello,
              >>
              >If i take a jpeg and pipe it from a binary reader to a binary writer,
              >everything is fine and I can still use it.
              >If i take that same jpeg and piping code and simply add a byte encoded
              >string to the front of the file then I can no longer open it in an image
              >editor. This i would expect.
              >>
              >However if i open that image in notebook and remove the string I entered,
              >then i still cant open the file in an image editor, does anyone know why
              >this is?? Once ive removed the 4 character string with notepad the files
              >are
              >"seemingly" exactly the same?? They have precisely the same file size
              >(down
              >to the byte) and the bytes within the file are also exactly the same??
              >>
              >Whats different?
              >>
              >Thanks
              >>
              >>
              >>
              >>

                Comment

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