1997.01.23 00:04 "Re: Reading from standard in", by Tom Lane
You could do it with something like TIFFFdOpen(fileno(stdin), ...) but as several others have pointed out, it'll fail if stdin is attached to anything that doesn't support seeking. Likewise for writing to stdout.
So generally speaking, you can't deal with anything but a disk file; the apparent flexibility of stdin/stdout isn't there, because you can't pipe TIFF data to or from a different process.
I'd suggest logic along the lines of copying data from stdin to a temp file until reaching EOF, then doing TIFFOpen on the temp file; or the obvious inverse for writing. This will work when piped. If you wanted to be really smart you could try to detect whether stdin supports seeking and avoid the file copy when it does. (Not sure how you could portably make the same test for stdout, though.)
regards, tom lane