Eric Weeks - personal pages - graphics techniques

Color Postscript tutorial

(follow above link to Graphics Techniques to see earlier postscript tutorials)

weeks@physics.emory.edu

Color PostScript is trivial. For black & white pictures, you specify shades of gray with the command "setgray". "0 setgray" is black and "1 setgray" is white. For color PostScript, you can specify the color with the command "setrgbcolor". You give that command 3 numbers, the red, green, and blue levels. Thus:

Command Color

1 0 0 setrgbcolor red

0 1 0 setrgbcolor green

0 0 1 setrgbcolor dark blue

0 1 1 setrgbcolor light blue

1 0 1 setrgbcolor magenta

1 1 0 setrgbcolor yellow

1 1 1 setrgbcolor white

0 0 0 setrgbcolor black

1.0 0.7 0.0 setrgbcolor orange

0.7 0.3 1.0 setrgbcolor purple

0.7 0.3 0.0 setrgbcolor brown

0.0 0.5 0.0 setrgbcolor dark green

Command	Color
1 0 0 setrgbcolor	red
0 1 0 setrgbcolor	green
0 0 1 setrgbcolor	dark blue
0 1 1 setrgbcolor	light blue
1 0 1 setrgbcolor	magenta
1 1 0 setrgbcolor	yellow
1 1 1 setrgbcolor	white
0 0 0 setrgbcolor	black
1.0 0.7 0.0 setrgbcolor	orange
0.7 0.3 1.0 setrgbcolor	purple
0.7 0.3 0.0 setrgbcolor	brown
0.0 0.5 0.0 setrgbcolor	dark green

This table I got from looking at what the output is on one particular color printer; this is not from a book, so take it with a grain of salt. Or, preferably, generate your own color table with the following program. (Or just download the color table in Postscript form.)

This is a program I wrote which prints out squares of color along with the RGB values the program used to generate each square. Very useful for picking colors.

Click here to get this program.

To compile, "gcc -o palette palette2.c". This program won't compile using "cc" because it doesn't like how I printed out large chunks of text; this is easy to fix yourself if you don't have gcc. You'll need to edit the functions "printheader()" and "printtrailer()" to give each line of text its own printf() statement.

This program makes a page that looks something like this:

Click here to download the postscript file that produces this page -- you don't necessarily need the program, just this page.

Questions?

What if you don't have a color printer? No problem; you don't have to actually print PostScript pictures for them to be useful. You can easily convert PostScript pictures to other formats and put them on your web page; click here for more information.

Yes, I know the color chart is slightly redundant; what I do is show gradations in color between nine different "nice" colors (red, green, dk blue, lt blue, yellow, magenta, white, black, and medium gray). With nine target colors there are 9*8/2=36 different pairs of colors to show the gradations between. I show 5 colors between each pair of "nice" colors, for a total of 216 boxes; the "nice" colors are each repeated four times.

Links...

Eric's Home Page
Information on Software -- Other programs available like this one
Pictures I've Made
Graphics Techniques
site map
Email me if you have questions, problems, or encouragement. My email address is below.

Current address:
Eric R. Weeks
weeks(circle a)physics.emory.edu
Department of Physics
Emory University
Atlanta, GA 30322-2430