1. Color Spaces

PostScript supports multiple color spaces for representing colors, from simple grayscale to complex device-independent color systems. Understanding color spaces is crucial for accurate color reproduction and professional printing.

1.1. Overview

PostScript color spaces include:

  • DeviceGray - Grayscale (0-1)

  • DeviceRGB - Red-Green-Blue (0-1 each)

  • DeviceCMYK - Cyan-Magenta-Yellow-Black (0-1 each)

  • HSB - Hue-Saturation-Brightness (Level 1 compatible)

  • CIE-based - Device-independent color (Level 2+)

  • Pattern - Repeating patterns (Level 2+)

  • Indexed - Color lookup tables (Level 2+)

  • Separation - Spot colors (Level 2+)

Each color space has specific use cases and characteristics.

1.2. Device Color Spaces

1.2.1. DeviceGray

Grayscale color space using single value:

% setgray: gray setgray
% gray: 0 (black) to 1 (white)

0 setgray        % Black
0.5 setgray      % 50% gray
1 setgray        % White

% Query current gray
currentgray =    % Returns current gray value

Common gray values:

/Black { 0 setgray } def
/White { 1 setgray } def
/LightGray { 0.75 setgray } def
/MediumGray { 0.5 setgray } def
/DarkGray { 0.25 setgray } def

1.2.2. DeviceRGB

RGB color space (additive color model):

% setrgbcolor: red green blue setrgbcolor
% Each component: 0 (none) to 1 (full)

1 0 0 setrgbcolor    % Red
0 1 0 setrgbcolor    % Green
0 0 1 setrgbcolor    % Blue
1 1 0 setrgbcolor    % Yellow
1 0 1 setrgbcolor    % Magenta
0 1 1 setrgbcolor    % Cyan
0 0 0 setrgbcolor    % Black
1 1 1 setrgbcolor    % White

% Query current RGB
currentrgbcolor      % Returns: r g b

Common colors:

% Primary colors
/Red { 1 0 0 setrgbcolor } def
/Green { 0 1 0 setrgbcolor } def
/Blue { 0 0 1 setrgbcolor } def

% Secondary colors
/Yellow { 1 1 0 setrgbcolor } def
/Magenta { 1 0 1 setrgbcolor } def
/Cyan { 0 1 1 setrgbcolor } def

% Named colors
/Orange { 1 0.647 0 setrgbcolor } def
/Purple { 0.502 0 0.502 setrgbcolor } def
/Brown { 0.647 0.165 0.165 setrgbcolor } def
/Pink { 1 0.753 0.796 setrgbcolor } def

1.2.3. DeviceCMYK

CMYK color space (subtractive color model for printing):

% setcmykcolor: cyan magenta yellow black setcmykcolor
% Each component: 0 (none) to 1 (full)

1 0 0 0 setcmykcolor    % Cyan
0 1 0 0 setcmykcolor    % Magenta
0 0 1 0 setcmykcolor    % Yellow
0 0 0 1 setcmykcolor    % Black

% Query current CMYK
currentcmykcolor        % Returns: c m y k

RGB to CMYK conversion (simple):

/rgb2cmyk {  % r g b -> c m y k
  3 dict begin
    /b exch def
    /g exch def
    /r exch def

    % Calculate K
    /k 1 r max g max b max max sub def

    % Calculate CMY
    k 1 eq {
      % Pure black
      0 0 0 k
    } {
      % Calculate C, M, Y
      1 r sub k sub 1 k sub div
      1 g sub k sub 1 k sub div
      1 b sub k sub 1 k sub div
      k
    } ifelse
  end
} def

% Usage
0.8 0.2 0.3 rgb2cmyk setcmykcolor

1.2.4. HSB (Hue-Saturation-Brightness)

Alternative color representation:

% sethsbcolor: hue saturation brightness sethsbcolor
% hue: 0-360 degrees
% saturation: 0 (gray) to 1 (pure)
% brightness: 0 (black) to 1 (bright)

0 1 1 sethsbcolor      % Red (hue=0°)
120 1 1 sethsbcolor    % Green (hue=120°)
240 1 1 sethsbcolor    % Blue (hue=240°)
60 1 1 sethsbcolor     % Yellow (hue=60°)

% Pastel colors (low saturation)
0 0.3 1 sethsbcolor    % Pastel red

% Dark colors (low brightness)
240 1 0.5 sethsbcolor  % Dark blue

% Query current HSB
currenthsbcolor        % Returns: h s b

Color wheel using HSB:

/colorWheel {  % centerX centerY radius -> -
  3 dict begin
    /r exch def
    /cy exch def
    /cx exch def

    0 10 360 {
      /angle exch def

      gsave
        cx cy translate
        angle rotate

        % Set color based on angle
        angle 1 1 sethsbcolor

        % Draw segment
        newpath
        0 0 moveto
        r 0 lineto
        r 0 r 0 10 arc
        closepath
        fill
      grestore
    } for
  end
} def

200 200 100 colorWheel

1.3. Color Conversions

1.3.1. RGB to HSB 

/rgb2hsb {  % r g b -> h s b
  3 dict begin
    /b exch def
    /g exch def
    /r exch def

    % Find max and min
    /cmax r g max b max def
    /cmin r g min b min def
    /delta cmax cmin sub def

    % Calculate hue
    delta 0 eq {
      /h 0 def
    } {
      cmax r eq {
        /h g b sub delta div 60 mul def
      } {
        cmax g eq {
          /h b r sub delta div 2 add 60 mul def
        } {
          /h r g sub delta div 4 add 60 mul def
        } ifelse
      } ifelse
    } ifelse

    h 0 lt { /h h 360 add def } if

    % Calculate saturation
    /s cmax 0 eq { 0 } { delta cmax div } ifelse def

    % Brightness is max
    /v cmax def

    h s v
  end
} def

% Usage
1 0.5 0 rgb2hsb  % Returns hue, sat, bright

1.3.2. HSB to RGB 

/hsb2rgb {  % h s b -> r g b
  3 dict begin
    /v exch def
    /s exch def
    /h exch def

    s 0 eq {
      % Achromatic (gray)
      v v v
    } {
      h 360 ge { /h h 360 sub def } if
      h 0 lt { /h h 360 add def } if

      /h h 60 div def
      /i h floor cvi def
      /f h i sub def

      /p v 1 s sub mul def
      /q v 1 s f mul sub mul def
      /t v 1 s 1 f sub mul sub mul def

      i 0 eq { v t p } if
      i 1 eq { q v p } if
      i 2 eq { p v t } if
      i 3 eq { p q v } if
      i 4 eq { t p v } if
      i 5 eq { v p q } if
    } ifelse
  end
} def

1.3.3. CMYK to RGB (Approximate) 

/cmyk2rgb {  % c m y k -> r g b
  4 dict begin
    /k exch def
    /y exch def
    /m exch def
    /c exch def

    1 c k add 1 k sub mul sub
    1 m k add 1 k sub mul sub
    1 y k add 1 k sub mul sub
  end
} def

1.4. Color Palettes

1.4.1. Predefined Palettes 

% Web colors
/webColors <<
  /AliceBlue [0.941 0.973 1.000]
  /AntiqueWhite [0.980 0.922 0.843]
  /Aqua [0.000 1.000 1.000]
  /Azure [0.941 1.000 1.000]
  /Beige [0.961 0.961 0.863]
  /Crimson [0.863 0.078 0.235]
  /Gold [1.000 0.843 0.000]
  /Indigo [0.294 0.000 0.510]
  /Lavender [0.902 0.902 0.980]
  /Navy [0.000 0.000 0.502]
  /Olive [0.502 0.502 0.000]
  /Orange [1.000 0.647 0.000]
  /Pink [1.000 0.753 0.796]
  /Purple [0.502 0.000 0.502]
  /Silver [0.753 0.753 0.753]
  /Teal [0.000 0.502 0.502]
  /Violet [0.933 0.510 0.933]
>> def

/setWebColor {  % colorName -> -
  webColors exch get
  aload pop setrgbcolor
} def

% Usage
/Crimson setWebColor
100 100 50 0 360 arc fill

1.4.2. Material Design Palette 

/materialColors <<
  /Red50 [1.000 0.922 0.933]
  /Red500 [0.957 0.263 0.212]
  /Red900 [0.718 0.110 0.110]

  /Blue50 [0.890 0.949 0.992]
  /Blue500 [0.129 0.588 0.953]
  /Blue900 [0.051 0.278 0.631]

  /Green50 [0.910 0.961 0.914]
  /Green500 [0.298 0.686 0.314]
  /Green900 [0.106 0.369 0.125]
>> def

1.4.3. Gradient Palettes 

/createGradient {  % color1 color2 steps -> gradientArray
  3 dict begin
    /steps exch def
    /c2 exch def
    /c1 exch def

    [
      0 1 steps 1 sub {
        /i exch def
        /t i steps 1 sub div def

        [
          c1 0 get 1 t sub mul c2 0 get t mul add
          c1 1 get 1 t sub mul c2 1 get t mul add
          c1 2 get 1 t sub mul c2 2 get t mul add
        ]
      } for
    ]
  end
} def

% Usage
[1 0 0] [0 0 1] 10 createGradient
% Returns array of 10 colors from red to blue

1.5. Color Manipulation

1.5.1. Lighten/Darken 

/lighten {  % amount r g b -> r' g' b'
  4 dict begin
    /b exch def
    /g exch def
    /r exch def
    /amt exch def

    r amt add 1 min
    g amt add 1 min
    b amt add 1 min
  end
} def

/darken {  % amount r g b -> r' g' b'
  4 dict begin
    /b exch def
    /g exch def
    /r exch def
    /amt exch def

    r amt sub 0 max
    g amt sub 0 max
    b amt sub 0 max
  end
} def

% Usage
0.2 1 0.5 0 lighten setrgbcolor  % Lighten orange
0.2 1 0.5 0 darken setrgbcolor   % Darken orange

1.5.2. Saturation Adjustment 

/saturate {  % amount r g b -> r' g' b'
  4 dict begin
    /b exch def
    /g exch def
    /r exch def
    /amt exch def

    % Convert to HSB
    r g b rgb2hsb

    % Adjust saturation
    3 1 roll
    amt add 0 max 1 min
    3 -1 roll

    % Convert back to RGB
    hsb2rgb
  end
} def

1.5.3. Color Blending 

/blendColors {  % r1 g1 b1 r2 g2 b2 t -> r g b
  7 dict begin
    /t exch def
    /b2 exch def /g2 exch def /r2 exch def
    /b1 exch def /g1 exch def /r1 exch def

    r1 1 t sub mul r2 t mul add
    g1 1 t sub mul g2 t mul add
    b1 1 t sub mul b2 t mul add
  end
} def

% Usage
1 0 0  0 0 1  0.5 blendColors  % 50% red, 50% blue
setrgbcolor

1.6. Advanced Color Techniques

1.6.1. Color Harmonies 

% Complementary colors (opposite on color wheel)
/complementary {  % h s b -> h1 s1 b1 h2 s2 b2
  3 copy
  3 -1 roll 180 add 360 mod
  3 1 roll
} def

% Triadic colors (120° apart)
/triadic {  % h s b -> [h1 s1 b1] [h2 s2 b2] [h3 s3 b3]
  3 dict begin
    /b exch def
    /s exch def
    /h exch def

    [
      [h s b]
      [h 120 add 360 mod s b]
      [h 240 add 360 mod s b]
    ]
  end
} def

% Usage
0 1 1 triadic {
  aload pop sethsbcolor
  % Draw something with this color
} forall

1.6.2. Color Temperature 

% Warm/cool color filter
/warmFilter {  % r g b -> r' g' b'
  % Increase red, decrease blue
  3 1 roll
  0.9 mul
  3 -1 roll
  1.1 mul 1 min
  3 1 roll
} def

/coolFilter {  % r g b -> r' g' b'
  % Decrease red, increase blue
  exch
  1.1 mul 1 min
  exch
  0.9 mul
} def

1.6.3. Grayscale Conversion 

% Luminance-based grayscale
/toGrayscale {  % r g b -> gray
  0.299 mul     % Red weight
  exch 0.587 mul add  % Green weight
  exch 0.114 mul add  % Blue weight
} def

% Usage
1 0.5 0 toGrayscale setgray

1.7. Color Matching and Gamut

1.7.1. Color Difference 

% Calculate color difference (Euclidean distance in RGB)
/colorDifference {  % r1 g1 b1 r2 g2 b2 -> distance
  6 dict begin
    /b2 exch def /g2 exch def /r2 exch def
    /b1 exch def /g1 exch def /r1 exch def

    r2 r1 sub dup mul
    g2 g1 sub dup mul add
    b2 b1 sub dup mul add
    sqrt
  end
} def

% Find closest color in palette
/findClosestColor {  % r g b palette -> index
  4 dict begin
    /pal exch def
    /tb exch def /tg exch def /tr exch def

    /minDist 999 def
    /minIdx 0 def

    0 1 pal length 1 sub {
      /i exch def
      tr tg tb
      pal i get aload pop
      colorDifference

      dup minDist lt {
        /minDist exch def
        /minIdx i def
      } {
        pop
      } ifelse
    } for

    minIdx
  end
} def

1.7.2. Gamut Clamping 

% Clamp RGB values to valid range
/clampRGB {  % r g b -> r' g' b'
  3 {
    0 max 1 min
  } repeat
} def

% Clamp while preserving hue
/clampPreservingHue {  % r g b -> r' g' b'
  3 dict begin
    /b exch def /g exch def /r exch def

    % Find max component
    /maxVal r g max b max def

    maxVal 1 gt {
      % Scale down proportionally
      r maxVal div
      g maxVal div
      b maxVal div
    } {
      r g b
    } ifelse
  end
} def

1.8. Practical Color Examples

1.8.1. Example 1: Heat Map 

/heatMapColor {  % value(0-1) -> -
  % Blue -> Cyan -> Green -> Yellow -> Red
  dup 0.25 lt {
    % Blue to Cyan
    4 mul
    0 exch 1 setrgbcolor
  } {
    dup 0.5 lt {
      % Cyan to Green
      0.25 sub 4 mul
      1 exch sub exch 1 exch setrgbcolor
    } {
      dup 0.75 lt {
        % Green to Yellow
        0.5 sub 4 mul
        dup 1 0 setrgbcolor
      } {
        % Yellow to Red
        0.75 sub 4 mul
        1 exch 1 exch sub 0 setrgbcolor
      } ifelse
    } ifelse
  } ifelse
} def

% Draw heat map
0 0.05 1 {
  /v exch def
  v heatMapColor
  v 100 mul 100 10 50 rectfill
} for

1.8.2. Example 2: Rainbow Gradient 

/rainbowGradient {  % x y width height -> -
  4 dict begin
    /h exch def /w exch def
    /y exch def /x exch def

    0 1 w {
      /i exch def
      i w div 360 mul 1 1 sethsbcolor
      x i add y 1 h rectfill
    } for
  end
} def

100 100 400 50 rainbowGradient

1.8.3. Example 3: Color Picker 

/colorPicker {  % centerX centerY size -> -
  3 dict begin
    /size exch def
    /cy exch def
    /cx exch def

    % Draw hue/saturation square
    0 1 size {
      /x exch def
      0 1 size {
        /y exch def

        /hue x size div 360 mul def
        /sat y size div def

        hue sat 1 sethsbcolor
        cx x add cy y add 1 1 rectfill
      } for
    } for
  end
} def

100 100 200 colorPicker

1.8.4. Example 4: Duotone Effect 

/duotone {  % grayValue color1 color2 -> -
  % Blend between two colors based on grayscale
  3 dict begin
    /c2 exch def
    /c1 exch def
    /gray exch def

    c1 aload pop
    c2 aload pop
    gray
    blendColors
    setrgbcolor
  end
} def

% Usage
0.3 [0.1 0.2 0.4] [0.9 0.7 0.5] duotone
100 100 50 50 rectfill

1.9. Color Accessibility

1.9.1. Contrast Ratio 

% Calculate relative luminance
/luminance {  % r g b -> L
  3 dict begin
    /b exch def /g exch def /r exch def

    % sRGB to linear RGB
    /toLinear {
      dup 0.03928 le {
        12.92 div
      } {
        0.055 add 1.055 div 2.4 exp
      } ifelse
    } def

    r toLinear 0.2126 mul
    g toLinear 0.7152 mul add
    b toLinear 0.0722 mul add
  end
} def

% Calculate contrast ratio
/contrastRatio {  % r1 g1 b1 r2 g2 b2 -> ratio
  2 dict begin
    /L2 3 -1 roll 3 -1 roll 3 -1 roll luminance def
    /L1 3 -1 roll 3 -1 roll 3 -1 roll luminance def

    L1 L2 gt {
      L1 0.05 add L2 0.05 add div
    } {
      L2 0.05 add L1 0.05 add div
    } ifelse
  end
} def

% Check if contrast is sufficient (WCAG AA: 4.5:1 for normal text)
/hasGoodContrast {  % r1 g1 b1 r2 g2 b2 -> boolean
  contrastRatio 4.5 ge
} def

1.9.2. Colorblind-Safe Palettes 

% Colorblind-friendly palette
/cbSafe <<
  /Blue [0.000 0.447 0.698]
  /Orange [0.902 0.624 0.000]
  /Green [0.000 0.620 0.451]
  /Yellow [0.941 0.894 0.259]
  /DarkBlue [0.000 0.000 0.545]
  /Purple [0.800 0.475 0.655]
  /Pink [0.941 0.502 0.502]
>> def

1.10. Performance Optimization

1.10.1. Color Caching 

% Cache commonly-used colors
/colorCache 100 dict def

/getCachedColor {  % name r g b -> -
  4 dict begin
    /b exch def /g exch def /r exch def
    /name exch def

    colorCache name known not {
      colorCache name [r g b] put
    } if

    colorCache name get aload pop setrgbcolor
  end
} def

% Usage
/MyBlue 0.2 0.4 0.8 getCachedColor

1.10.2. Minimize Color Changes 

% Good: batch by color
1 0 0 setrgbcolor
shape1 fill
shape2 fill
shape3 fill

0 0 1 setrgbcolor
shape4 fill
shape5 fill

% Less efficient: frequent changes
1 0 0 setrgbcolor shape1 fill
0 0 1 setrgbcolor shape2 fill
1 0 0 setrgbcolor shape3 fill
0 0 1 setrgbcolor shape4 fill

1.11. Best Practices

1.11.1. Use Meaningful Color Names 

% Good: descriptive names
/BrandPrimary { 0.2 0.4 0.8 setrgbcolor } def
/BrandSecondary { 1.0 0.6 0.0 setrgbcolor } def
/TextDark { 0.2 setgray } def
/Background { 0.95 setgray } def

% Bad: generic names
/Color1 { 0.2 0.4 0.8 setrgbcolor } def
/C2 { 1.0 0.6 0.0 setrgbcolor } def

1.11.2. Consistent Color Scheme 

% Define theme colors
/theme <<
  /primary [0.129 0.588 0.953]
  /secondary [0.957 0.263 0.212]
  /success [0.298 0.686 0.314]
  /warning [1.000 0.596 0.000]
  /error [0.957 0.263 0.212]
  /text [0.129 0.129 0.129]
  /background [1.000 1.000 1.000]
>> def

/useThemeColor {  % colorName -> -
  theme exch get aload pop setrgbcolor
} def

% Usage
/primary useThemeColor

1.11.3. Test Color Output 

% Draw color swatches for testing
/drawSwatch {  % x y width height r g b label -> -
  8 dict begin
    /label exch def
    /b exch def /g exch def /r exch def
    /h exch def /w exch def
    /y exch def /x exch def

    % Color rectangle
    r g b setrgbcolor
    x y w h rectfill

    % Border
    0 setgray
    0.5 setlinewidth
    x y w h rectstroke

    % Label
    /Helvetica findfont 8 scalefont setfont
    x 2 add y h add 10 add moveto
    label show
  end
} def

% Test palette
100 100 50 50 1 0 0 (Red) drawSwatch
160 100 50 50 0 1 0 (Green) drawSwatch
220 100 50 50 0 0 1 (Blue) drawSwatch

1.12. Common Pitfalls

1.12.1. Color Values Out of Range 

% Wrong: values > 1
2 0.5 0 setrgbcolor  % Invalid!

% Correct: clamp to 0-1
2 0.5 0 clampRGB setrgbcolor

1.12.2. Mixing Color Spaces 

% Wrong: mixed color commands
1 0 0 setrgbcolor
0.5 setgray  % Overwrites RGB setting!

% Correct: consistent color space
1 0 0 setrgbcolor
% ... draw with RGB
0 0 0 setrgbcolor  % Still in RGB

1.12.3. Forgetting Color Restoration 

% Wrong: color persists
1 0 0 setrgbcolor
shape1 fill
% Everything after is red!

% Correct: save/restore
gsave
  1 0 0 setrgbcolor
  shape1 fill
grestore
% Color restored

1.13. See Also

Back to top

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