These are files that we receive from clients in the mining industry, though I'm not entirely sure which software is used to export the image and grf file. Apart from the first 3 lines (Position X, Z, Y) the next 8 lines are unknown to me. The two number preceding each coordinate point look to be the pixel dimensions based off a 0,0 origin.
Since we often get multitudes of these files, I'm hoping there's a way to parse the grf file for just those 4 coordinate points in order to map a plane in C4D while ignoring the rest of the values in the file. It's been a crazy busy week, so apologies for only circling back to this now!