What do you do if you have a plot of the data you need, but not the data itself?

This video shows how Unplot solves this problem:

I found myself in the situation where I had a plot of the data, but not the actual coordinates of the data itself. So, today I wrote this little tool for turning a bitmap image into the x and y coordinates of the curve. (Some Photoshop work may be necessary for cleaning out other lines in the image). It simply takes the image, starts at the top, and scans downwards until it hits the curve, and then works from left to right. The data can be saved as CSV, to be easily loaded into Excel or Matlab.

It works on figures from research papers, which has been useful. Also, I can use it as a quick way to get audio data from Audacity.

Here is the program (897K). Currently Windows only.