QTR-Quadtone RIP

The process is hard to explain without a little more info on what you mean by linearizing with a text file. 

In a sense, you don't linearize anything with the text file. You simply enter the measurements from the printed target into a text file. The QTR curve creation program does the linearizing

Measurement files are basically tab delimited text files. The can contain either Density measurements on separate lines, or L*a*b* measurements on separate lines. You can make them by hand from entering measurements from a densitometer or generate them with an spectrometer and measurement software. 

When you "drop" a measurement file onto the linearize-data app you will get a text based graph of the measurements and they will be concatenated into a string that begins LINEARIZE="measurement measurement measurement etc..."

The linearization is done when you install the profile and the curve creation program does its thing. After all the partitioning and temp curve creation the curve creation program takes those measurements in the LINEARIZE= line and makes a straight line between the first value and the last value. It then and generates a reverse correction curve for each of of the in-between values so they will produce the correct density on that straight line when printed. 

There is another option of linearing the quad file with the linearize-quad app but that doesn't seem to be what you're asking about.

Hope that helps,
Richard Boutwell

www.RichardBoutwell.com
www.BWMastery.com