Selecting a PostScript Background Color

QUESTION: I can get any background color I like in my PostScript file as long as it's white. Can I choose another background color?

ANSWER: The !P.BACKGROUND system variable is set to 255 when you make the PostScript device active. But it doesn't matter what color you load into color index 255, you still get a white background on your PostScript plot! In other words, the color you load into index 255 can be used for other things (as a drawing color, for example), but it doesn't affect the background color of the plot.

There is only one way to get a background color different from white in a PostScript file, and that is essentially to draw an image of a single color in the PostScript window. I like to use POLYFILL for this purpose, like this:

   TVLCT, [255,0], [0,255], [0,0], !D.TABLE_SIZE-2
   greenColor = !D.TABLE_SIZE-1
   redColor = !D.TABLE_SIZE-2
   POLYFILL, [1,1,0,0,1], [1,0,0,1,1], /NORMAL, COLOR=greenColor
   PLOT, data, COLOR=redColor, /NOERASE

Another way would be to use the TV command like this:

   image = REPLICATE(greenColor, 2, 2)
   TV, image, XSIZE=!D.X_SIZE, YSIZE=!D.Y_SIZE
   PLOT, data, COLOR=redColor, /NOERASE