Graphics are imbedded in RTF in either a binary format or an (ASCII) hex dump of that binary. I have never seen a binary format graphic - I don't think that the filter will process binary correctly. It does handle the hex format of graphics, by converting the hex back into binary and writing the binary to a file. The file extension is chosen by looking at the original type of the graphic. The following list shows the file types and their extensions:
In addition, the filter produces a link to the file containing the graphic. Now, since the above graphic formats are not very portable, the filter assumes that you will convert these files to something more useful, like GIF. So the format of the link is:
<a href="basenameN.ext">Click here for a Picture</a>
where
Since most Web browser only support images in GIF-format, you will have to convert the generated PICT- and WMF-files to GIF. For PICT there is picttoppm/ppmtogif, but for WMF? I don't know of any WMF translators for Unix; for DOS there is wmf2bmp, whose output could then be converted to GIF via the pbmplus-tools. From what I understand, WMF is not a pixel- but a vector-graphic format, so maybe it would be easier to translate WMF to Postscript and then let Ghostscript do the job of converting to GIF. Any volunteers for writing a wmftops utility?
You can also change the link to an IMG form. If you specify the -I command line option, all links to graphics will be of the form:
<IMG src="basenameN.ext">
There is one other special case. If a graphic is encountered when the filter is in the process of generating a link, the IMG form of the link is used even without the -I command line option.