README
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22
23A program that can be used to display a matrix as a gray scale image on PostScript
24printers. May be useful if you have a large matrix and want a simple way to look
25for patterns. Although I haven't been anywhere close, I expect a 600x600 matrix
26is a very optimistic upper bound on a 300 dpi printer using 5 shades of gray and
278.5x11 inch paper.
28
29Matrix elements are a series of floating point numbers arranged in the input file
30in row major order. By default each matrix is assumed to be square and the number
31of rows (and columns) is set to the square root of the number of elements in the
32input file. White space, including newlines, is not used to determine the matrix
33dimensions. Each matrix element is mapped into an integer in the range 0 to 255
34(254 by default) and PostScript's image operator maps that integer into a gray
35scale appropriate for your printer.
36
37The mapping from floating point matrix elements to integers is controlled by an
38interval list and grayscale map. The default interval list is "-1,0,1" which
39partitions the real line into 7 regions, while the default grayscale map gets
40darker as the regions move from left to right along the real line. The -i option
41changes the interval list and the -g option modifies the grayscale mapping. Check
42the man page for more details.
43
44By default 6 byte patterns are used, but any number can be selected with the -b
45option. 6 byte patterns are a tradeoff that achieves a good (but not necessarily
46optimal) performance across the wide variety of currently available PostScript
47printers. Decreasing the pattern size often helps some on printers with fast
48processors (eg. PS-810s) while increasing the pattern size speeds things up on
49older printers (eg. PS-800s). In the limited number of tests I ran -b10 worked
50best on PS800s and -b4 gave the best performance on PS-810s. If you want a
51different default pattern size change the initialization of bytespp (near line
52175 in postmd.c) before you compile the program.
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