(Possibly the wrong place to ask this sort of question, but...)
We have a need to provide custom image decode filters for the standard image types. For most of them, this is easy enough using standard IE facilities to register the filters against the appropriate MIME types. Unfortunately (for our purposes), image/gif, image/jpeg, and image/pjpeg are special cased by IE, so that even if an image decode filter is registered for one of them, it is ignored, and the build in renderer is used. (It would be nice if IE checked for an explicitly registered decoder, and use the built-in one only if a custom one wasn't registered, but that's not the case...)
We currently fake this out by hooking the FindMimeFromData() function to return custom image MIME types for these 3, and then registering our filters against these custom MIME types. This works OK for displaying these image types. Unfortunately, FindMimeFromData() is apparently also used by IE to determine the Content-type to return in the file data part of the multipart/form-data returned for an INPUT Type=file FORM, meaning that attempts to upload GIF or JPEG files will get our "funny" MIME types attached to them, which isn't OK. As far as I can tell, there doesn't appear to be enough info passed to FindMimeFromData() to allow our hook routine to determine why it is being called, so it can't return the "real" MIME types in the outbound case, and the "fake" MIME types in the inbound case. I was wondering if anyone has a suggestion for another way to solve this problem. I am not at all knowledgeable about IE extensions, but I have read some things implying that it may be possible to insert a filtering add-on that could find (and rewrite) the MIME types in the incoming stream. However, I haven't found any details or documentation that describes how to do something of this sort. A solution that isn't specific to a particular rev of IE would be preferred, but an IE7 only solution would be acceptable.
Anyone have any ideas for me
ted