Automatically converting pictures to black-and-white

Thanks to John Kormylo, I found a simple solution: just add these two lines at the Document preamble:

\usepackage{xcolor}
\selectcolormodel{gray}

Note that this changes only the colors generated internally in the document (including pspictures). It does not change the colors of included external graphic images.

The following also works for included eps images.

RGB to CMYK Put the following code into your preamble if you cannot change the PostScript code yourself.

\AtBeginDocument{\special{ps:
/setrgbcolor { 
  1 sub neg /Y exch def 
  1 sub neg /M exch def
  1 sub neg /C exch def 
  /K 1 def
  C K lt { /K C def } if
  M K lt { /K M def } if
  Y K lt { /K Y def } if
  K 1 eq { 0 0 0 }{ % Black 0 0 0 1
    /K1 1 K sub def
    C K sub K1 div M K sub K1 div Y K sub K1 div } ifelse
  K setcmykcolor
 } def 
}}

or/and RGB to GRAY

\AtBeginDocument{\special{ps:
/setrgbcolor { 0.07 mul exch 0.71 mul add exch 0.21 mul add setgray } def 
}}