Table of Contents

• 1. sethsbcolor
  • 1.1. Syntax
  • 1.2. Stack Effects
  • 1.3. Description
  • 1.4. PostScript Level
  • 1.5. Examples
  • 1.6. Common Use Cases
    • 1.6.1. Color Wheel Generation
    • 1.6.2. Tint Generation
    • 1.6.3. Shade Generation
    • 1.6.4. Color Harmony
  • 1.7. Common Pitfalls
  • 1.8. Error Conditions
  • 1.9. Implementation Notes
  • 1.10. HSB to RGB Conversion
  • 1.11. HSB Color Model
  • 1.12. Practical Color Selection
  • 1.13. See Also

1. sethsbcolor

Sets the current color using HSB (Hue-Saturation-Brightness) values.

1.1. Syntax

hue saturation brightness sethsbcolor → –

1.2. Stack Effects

Table 1. Before

Level	Object
2	hue (0.0 to 1.0, color angle/360°)
1	saturation (0.0 to 1.0, color purity)
0	brightness (0.0 to 1.0, color intensity)

Table 2. After

Level	Object
(empty)	Color space set to DeviceRGB with HSB-derived color

1.3. Description

sethsbcolor sets the color space to DeviceRGB and sets the current color using hue, saturation, and brightness components.

HSB components:

• Hue (0.0 to 1.0): Color type on the color wheel

  • 0.0 = red, 0.167 = yellow, 0.333 = green, 0.5 = cyan, 0.667 = blue, 0.833 = magenta, 1.0 = red (wraps)

• Saturation (0.0 to 1.0): Color purity

  • 0.0 = no color (gray), 1.0 = pure, vivid color

• Brightness (0.0 to 1.0): Color intensity

  • 0.0 = black, 1.0 = maximum brightness

HSB is not a color space in its own right, merely a means for entering RGB color values in a different coordinate system. The color value entered by sethsbcolor is immediately converted into the RGB model and used with the DeviceRGB color space.

sethsbcolor does not give a rangecheck error for values outside the range 0 to 1; it substitutes the nearest legal value.

1.4. PostScript Level

Level 1 and later

1.5. Examples

Primary colors

0.0   1 1 sethsbcolor  % Red
0.333 1 1 sethsbcolor  % Green
0.667 1 1 sethsbcolor  % Blue

Pastel colors (low saturation)

0.0   0.3 1.0 sethsbcolor  % Light pink
0.333 0.3 1.0 sethsbcolor  % Light green
0.667 0.3 1.0 sethsbcolor  % Light blue

Dark colors (low brightness)

0.0   1 0.3 sethsbcolor  % Dark red
0.333 1 0.3 sethsbcolor  % Dark green
0.667 1 0.3 sethsbcolor  % Dark blue

Grays (zero saturation)

0 0   0.0 sethsbcolor  % Black
0 0   0.5 sethsbcolor  % Mid gray
0 0   1.0 sethsbcolor  % White

1.6. Common Use Cases

1.6.1. Color Wheel Generation

/DrawColorWheel {
  0 10 360 {
    % Convert degrees to hue
    360 div
    1.0  % Full saturation
    1.0  % Full brightness
    sethsbcolor

    % Draw segment
    drawWedge
  } for
} def

1.6.2. Tint Generation

/GenerateTints {
  % hue on stack
  5 {
    % Create 5 tints
    dup           % hue
    0.2 mul       % saturation decreases
    1.0           % full brightness
    sethsbcolor
    drawSwatch
  } repeat
  pop
} def

1.6.3. Shade Generation

/GenerateShades {
  % hue on stack
  5 {
    dup           % hue
    1.0           % full saturation
    0.2 mul       % brightness decreases
    sethsbcolor
    drawSwatch
  } repeat
  pop
} def

1.6.4. Color Harmony

/ComplementaryPair {
  % hue
  dup 1 1 sethsbcolor
  drawShape1

  0.5 add  % Opposite on color wheel
  dup 1.0 gt { 1.0 sub } if
  1 1 sethsbcolor
  drawShape2
} def

/TriadicScheme {
  % hue
  dup 1 1 sethsbcolor
  drawShape1

  dup 0.333 add 1 1 sethsbcolor
  drawShape2

  0.667 add 1 1 sethsbcolor
  drawShape3
} def

1.7. Common Pitfalls

Immediately Converted to RGB - Color is stored as RGB, not HSB.

0.5 1 1 sethsbcolor    % Cyan via HSB
currentrgbcolor         % Returns 0 1 1 (RGB)
currenthsbcolor         % Returns 0.5 1 1 (converted back)

Values Clamped - Out-of-range values adjusted, not rejected.

1.5 0.5 0.8 sethsbcolor  % Hue becomes 0.5
0.5 1.5 0.8 sethsbcolor  % Saturation becomes 1.0
0.5 0.5 1.5 sethsbcolor  % Brightness becomes 1.0

Hue Wraps - Hue values wrap at 0.0 and 1.0.

1.2 1 1 sethsbcolor   % Hue becomes 0.2
-0.1 1 1 sethsbcolor  % Hue becomes 0.9

Color Space Changes - Changes to DeviceRGB color space.

0.5 setgray             % DeviceGray
0.5 1 1 sethsbcolor     % DeviceRGB (gray lost!)

Intuitive Color Selection - HSB is more intuitive than RGB for selecting colors.

1.8. Error Conditions

Error	Condition
[stackunderflow]	Fewer than 3 operands on stack
[typecheck]	Any operand not a number
[undefined]	Disabled in certain contexts

1.9. Implementation Notes

• Immediately converts to RGB internally

• Sets color space to DeviceRGB

• Values clamped to 0.0-1.0 range

• No actual HSB color space exists

• Fast operation (simple conversion)

• Widely supported (Level 1)

1.10. HSB to RGB Conversion

Conceptual algorithm:

% If saturation = 0 (achromatic)
brightness dup dup setrgbcolor

% Otherwise
% 1. Determine hue sector (0-5)
% 2. Calculate chroma and intermediate values
% 3. Map to RGB based on sector
% 4. Apply brightness scaling

1.11. HSB Color Model

Hue Circle

   Yellow
  0.167
    |
Green-+-Red
0.333 | 0.0/1.0
    |
   Cyan
   0.5
    |
 Blue-+-Magenta
 0.667| 0.833

Saturation Scale

0.0 = Gray (no color)
0.5 = Pastel (moderate color)
1.0 = Vivid (pure color)

Brightness Scale

0.0 = Black
0.5 = Medium
1.0 = Full brightness

1.12. Practical Color Selection

% Selecting colors intuitively:

% Vivid red
0.0 1.0 1.0 sethsbcolor

% Pastel blue
0.667 0.3 1.0 sethsbcolor

% Dark green
0.333 1.0 0.3 sethsbcolor

% Medium gray (saturation = 0)
0.0 0.0 0.5 sethsbcolor

1.13. See Also

• setrgbcolor - Set RGB color

• setgray - Set grayscale

• setcmykcolor - Set CMYK color (Level 2)

• currenthsbcolor - Get HSB color