The GTF XFree86 modeline generator is a utility for calculating VESA GTF modes. Given the desired horizontal and vertical resolutions and refresh rate (in Hz), the parameters for a matching VESA GTF mode are printed out. Two output formats are supported: mode lines suitable for the XFree86 XF86Config(5x) file, and mode parameters suitable for the Linux fbset(8) utility.
This utility is already distributed with XFree86 4.3; if you have XFree86 4.3, then you probably already have gtf installed on your system (run `which gtf` to check).
This program is based on the Generalized Timing Formula (GTF(TM)) Standard Version: 1.0, Revsion: 1.0. The GTF Excel(TM) spreadsheet, a sample (and the definitive) implementation of the GTF Timing Standard is available at ftp://ftp.vesa.org/pub/GTF/VTF_V1R1.xls
You can download the source code here: gtf.c
(you may need to Right-click and "Save Link As...", depending on your browser's configuration).
Compile the program with: `gcc gtf.c -o gtf -lm -Wall`