c41invert is a command-line tool to quickly convert scans of orange-backed colour negatives into positives. For me its main selling point is its lack of knobs to tweak; it uses sensible defaults to get sensible results; if a certain picture deserves a more perfectionist approach, there is a lot of graphics software that will help you achieve that. This tool is meant to give you extra time to use them.
It uses a similar technique to negfix8, although I wasn't aware of its existence at the time.
The tool samples the central section of the image, creating a histogram of colours for each colour channel. It then picks a suitably 'dark' and 'light' colour (the first and ninetynineth percentile, respectively)
c41invert convert -i inputfile.name -o outputfile.jpg
Output files are always written as JPEG at quality setting 95.
The option -s-curve uses a sigmoid function (an S-shaped curve) rather than a linear function; you might like it, I don't.