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A program that can be used to display a matrix as a gray scale image on PostScript

printers. May be useful if you have a large matrix and want a simple way to look

for patterns. Although I haven't been anywhere close, I expect a 600x600 matrix

is a very optimistic upper bound on a 300 dpi printer using 5 shades of gray and

8.5x11 inch paper.

Matrix elements are a series of floating point numbers arranged in the input file

in row major order. By default each matrix is assumed to be square and the number

of rows (and columns) is set to the square root of the number of elements in the

input file. White space, including newlines, is not used to determine the matrix

dimensions. Each matrix element is mapped into an integer in the range 0 to 255

(254 by default) and PostScript's image operator maps that integer into a gray

scale appropriate for your printer.

The mapping from floating point matrix elements to integers is controlled by an

interval list and grayscale map. The default interval list is "-1,0,1" which

partitions the real line into 7 regions, while the default grayscale map gets

darker as the regions move from left to right along the real line. The -i option

changes the interval list and the -g option modifies the grayscale mapping. Check

the man page for more details.

By default 6 byte patterns are used, but any number can be selected with the -b

option. 6 byte patterns are a tradeoff that achieves a good (but not necessarily

optimal) performance across the wide variety of currently available PostScript

printers. Decreasing the pattern size often helps some on printers with fast

processors (eg. PS-810s) while increasing the pattern size speeds things up on

older printers (eg. PS-800s). In the limited number of tests I ran -b10 worked

best on PS800s and -b4 gave the best performance on PS-810s. If you want a

different default pattern size change the initialization of bytespp (near line

175 in postmd.c) before you compile the program.