Just append "ps2png ps2gif latex2gif" to "dobin tth" This is needed for tth -e and also the man page cites these binaries.
These script requires addionational dependencies: # ps2png file.ps file.png Calling ghostscript to convert, please wait ... /usr/bin/ps2png: line 12: gs: command not found /usr/bin/ps2png: line 12: pnmcrop: command not found /usr/bin/ps2png: line 12: pnmmargin: command not found /usr/bin/ps2png: line 12: pnmtopng: command not found like media-libs/netpbm and app-text/ghostscript-esp (or app-text/ghostscript-gpl)
fixed and updated to 3.77, thanks for reporting !