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Last spring I tried to use netpbm utilities to convert the DIFAX maps that we receive via IDD in g3 (FAX) format to postscript, with unsatisfactory results. Many of the images were chopped off, and most were too small. I experimented with all of the command-line options described in the netpbm man pages, to little effect. At that time, Mark Franklin of Alden was also on the trail of a satisfactory method to do the conversion, but he doesn't seem to have succeeded either, in spite of his vow to get to the bottom of the problem--I haven't heard from him since. There may be a relatively simple technical fix to the netpbm program "g3otpbm" that would solve the problem, but I don't speak C and I don't know enough about g3 format to attempt to modify the g3topbm code. I last looked at the mail archives on this subject at Unidata last spring, but didn't find anything of help. Has there been additional mail since then on this issue? Below I've included a script that contains most of my various attempts to get the netpbm routines to decode DIFAX products satisfactorily, in case you find if of any value. I haven't looked at in in a while so I don't know exactly in what state I left it. If you find a satisfactory conversion procedure, please share it! -- Dave
I'll just chime in a little here, also. We've been doing difax over IDD for about half a year now, and have had few problems, once we worked the kinks out. As previously stated, size of the images can be a problem. We solved most of those problems by using the pbmplus utilities to cut four panel images down into 4 different images (it's much better for viewing online, and quicker to load when my boss is teaching his forecasting classes). We also do cropping on some of the regular images, and crop down to the area that we're usually interested in. We also save the whole image each time, in case we need it for any reason. As previously noted, the images often need to be rotated 90 degrees, or have other things done to them, so I made up a little scheme were we have a configuration file for each difax product that we want to save. In the conf file, we are able to define the transformations that we want to do to each product. So, we can cut the images into panels, crop, rotate, and scale the images, all of which are easily done through the pnm routines. Whenever a difax product comes in over the IDD, it gets sent to a perl script I wrote, which does the stuff. It works well. Of course, there are occasional problems with getting the products over the IDD, but we haven't had too many problems. As for the the problem with g3topbm, does everybody use the -kludge option? When I've left it off in the past, things just don't work. Anyway, my scripts are far too messy for anyone else to read (they've sorta grown organically as our needs have changed here), but I'll attempt to answer any questions folks have... Dana dana@xxxxxxxxxxxxxxx