This matrix dataset is used by the PostScript driver to determine the imageable region of the output based on a specified paper size. The matrix has one row per paper size and four columns. Each row gives the X and Y coordinates for the lower left and upper right corners of the area of the paper onto which the PostScript printer can print. The coordinates are specified in the PostScript default coordinate system of 72 units per inch.
During device startup, this matrix is used in combination with the current ps.options(paper) setting to specify the default ps.options(region).
In order to find the imageable region for a new PostScript printer, send the following PostScript job to the printer: %! /buf 30 string def /pnum {buf cvs show} def /nl {currentpoint 16 sub exch pop 72 exch moveto} def /Helvetica findfont 14 scalefont setfont clippath pathbbox 72 360 moveto 4 -1 1 {-1 roll pnum nl} for showpage The four numbers that get printed may be used directly, in the order printed, as the region argument for the ps.options function.
# Default paper size? > ps.options()$paper [1] "letter" # Default region for the default paper size? > ps.paper.regions[ps.options()$paper,] llx lly urx ury 18 7.92 594 784.08