I have a bunch of *.tkf graphs that I have produced over the years and really don't want to have to rewrite the programs that produced them. Is there a way to change tkf graphs to, say, jpg graphs -- or other formats such as gif?
You can do this with the PQG graphics viewer. Double-click on vwr.exe to start the PQG graphics viewer. From the main viewer menu, select File->Open. This will bring up a Windows File Explorer. Locate the .tkf file that you would like to open.
Once you have a .tkf file loaded in the viewer, you can export it by selecting the "Convert" menu option. If you want something that is easy to load with a small file size like .gif, then you probably want to save the file as a Windows bitmap file with a .bmp file extension.