2008.11.21 20:29 "Re: [Tiff] Patch Legacy App for Updated libtiff?", by Kevin Myers

P.S. - Maybe some kind of "wrapper" could be written that provides an old libtiff interface to the legacy application then translates those calls as necessary to interface with the updated libtiff3.dll? Unfortunately, I know nothing about how to develop such a wrapper or how to figure out the interface differences between the different libtiff versions...

  ----- Original Message -----
  From: Kevin Myers

I have a legacy app that appears to use an older (potentially somewhat customized or stripped-down) version of libtiff. This legacy app is critical to the work that I do, and unfortunately alternative replacements are FAR out of my budget. I do *not* have access to the source code for this application.

This legacy app has a few limitations regarding handling of certain TIFF images that cause me a great deal of grief. In particular, it is unable to read JPEG or LZW compressed TIFF images. That is a very important issue for me, because many of the images that I work with are *extremely* large color images, and without the use of JPEG or LZW compression they require unacceptably huge amounts of disk space.

To resolve the above issues, I would like to find a way to somehow force the legacy app to use a recent version of libtiff that provides full handling for JPEG and LZW compressed images (among other things). In an overly simplistic attempt to accomplish this, I merely replaced the legacy application's copy of libtiff.dll with recent libtiff3.dll incarnations from GnuWin32 and tiff-3.8.2 Windows binary distributions. Unfortunately, that didn't work. During startup, the legacy app displays an error dialogue with the following message, then craters:

The procedure entgry point WriteScanLine could not be located in the dynamic library LIBTIFF.DLL.

Now I am pretty sure that WriteScanLine still exists in both of the libtiff3.dll incarnations that I attempted to substitute for the legacy apps version of libtiff.dll. So, the error message must be somewhat misleading. But I know practically nothing about how linkages between applications and DLLs work under Windows, so I have very little idea about what else might be causing this message, and if or how it can be fixed *without* access to the source code for the legacy app.

Can anyone offer any tips or suggestions that might help me solve this problem?

  Kevin M.

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