You can regard the .quad file as a compiled version of the raw code in the .qidf file (.txt file on a Mac). The .qidf file contains the basic parameters that define the curve and the .quad file contains the exact amount of ink that is applied from each channel for each luminosity level, which is what QTR uses to print. Piezography .quad files are generated from IJM's own software, and not from a .qidf.