Table of Contents

• 1. currenthsbcolor
  • 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 Lightening/Darkening
    • 1.6.2. Saturation Adjustment
    • 1.6.3. Hue Rotation
    • 1.6.4. Color Scheme Generation
  • 1.7. Common Pitfalls
  • 1.8. Error Conditions
  • 1.9. Implementation Notes
  • 1.10. HSB Color Model
  • 1.11. HSB to RGB Conversion
  • 1.12. See Also

1. currenthsbcolor

Returns current color as HSB values.

1.1. Syntax

– currenthsbcolor → hue saturation brightness

1.2. Stack Effects

Table 1. Before

Level	Object
(empty)	–

Table 2. After

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)

1.3. Description

currenthsbcolor returns the current color in the graphics state according to the hue-saturation-brightness model.

• If the current color space is DeviceRGB, currenthsbcolor returns the color values most recently specified by sethsbcolor, converting them from RGB to HSB coordinates if necessary.

• If the current color space is DeviceGray or DeviceCMYK, currenthsbcolor first converts the current color to RGB, then to HSB.

• For any other color space, currenthsbcolor returns 0.0 0.0 0.0 (black).

HSB components:

• Hue: Color type (0.0=red, 0.333=green, 0.667=blue, 1.0=red again)

• Saturation: Color purity (0.0=gray, 1.0=pure color)

• Brightness: Color intensity (0.0=black, 1.0=bright)

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 is internally stored as RGB.

1.4. PostScript Level

Level 1 and later

1.5. Examples

Querying current HSB color

0.5 1 1 sethsbcolor  % Cyan (hue=0.5)
currenthsbcolor
% Stack: 0.5 1.0 1.0

Converting from RGB

1 0 0 setrgbcolor  % Red
currenthsbcolor
% Stack: 0.0 1.0 1.0 (or 1.0 1.0 1.0 - hue wraps)

Saving and restoring color

currenthsbcolor            % Save current
/brightness exch def
/saturation exch def
/hue exch def

0.3 0.8 0.9 sethsbcolor   % Change color
drawShape

hue saturation brightness sethsbcolor  % Restore

Adjusting brightness

currenthsbcolor
0.5 mul                % Halve brightness
3 1 roll               % Reorder
sethsbcolor

1.6. Common Use Cases

1.6.1. Color Lightening/Darkening

/Lighten {
  % Increase brightness by 20%
  currenthsbcolor
  1.2 mul 1.0 min       % Brighten, cap at 1.0
  3 1 roll
  sethsbcolor
} def

/Darken {
  % Decrease brightness by 20%
  currenthsbcolor
  0.8 mul
  3 1 roll
  sethsbcolor
} def

1.6.2. Saturation Adjustment

/Desaturate {
  % Reduce saturation by half
  currenthsbcolor
  3 1 roll
  0.5 mul
  3 -1 roll
  sethsbcolor
} def

/Saturate {
  % Increase saturation
  currenthsbcolor
  3 1 roll
  1.5 mul 1.0 min
  3 -1 roll
  sethsbcolor
} def

1.6.3. Hue Rotation

/RotateHue {
  % delta
  currenthsbcolor
  3 2 roll
  add
  dup 1.0 gt { 1.0 sub } if
  dup 0.0 lt { 1.0 add } if
  3 -2 roll
  sethsbcolor
} def

% Example: rotate 120 degrees
0.333 RotateHue

1.6.4. Color Scheme Generation

/ComplementaryColor {
  currenthsbcolor
  3 2 roll
  0.5 add
  dup 1.0 gt { 1.0 sub } if
  3 -2 roll
  sethsbcolor
} def

/AnalogousColors {
  % Returns two analogous colors
  currenthsbcolor
  /b exch def /s exch def /h exch def

  % First analogous (+30°)
  h 0.083 add dup 1.0 gt { 1.0 sub } if
  s b sethsbcolor

  % Second analogous (-30°)
  h 0.083 sub dup 0.0 lt { 1.0 add } if
  s b sethsbcolor
} def

1.7. Common Pitfalls

HSB is RGB Entry Method - Color is actually stored as RGB internally.

0.5 1 1 sethsbcolor    % Cyan via HSB
currentrgbcolor         % Returns RGB values
% Stack: 0.0 1.0 1.0

Hue Wraps Around - Hue values wrap at 0.0 and 1.0.

1.2 0.8 0.9 sethsbcolor  % Hue becomes 0.2
-0.1 0.8 0.9 sethsbcolor % Hue becomes 0.9

Conversion Precision - RGB↔HSB conversion may lose precision.

0.123 0.456 0.789 sethsbcolor
currenthsbcolor
% May not be exactly 0.123 0.456 0.789

Gray Colors Undefined Hue - When saturation=0, hue is meaningless.

0.5 0.5 0.5 setrgbcolor  % Gray
currenthsbcolor
% Hue value is undefined (may be any value)

Use for Intuitive Color Selection - HSB is more intuitive than RGB for humans.

1.8. Error Conditions

Error	Condition
[stackoverflow]	Fewer than 3 free stack positions

1.9. Implementation Notes

• Fast query operation

• No modification to graphics state

• Values always in range 0.0 to 1.0

• Actually queries RGB, then converts

• Conversion is deterministic but approximate

• Hue undefined when saturation is 0

1.10. HSB Color Model

The HSB color model provides intuitive color selection:

Hue Values

0.0   = Red
0.167 = Yellow
0.333 = Green
0.5   = Cyan
0.667 = Blue
0.833 = Magenta
1.0   = Red (wraps)

Saturation Values

0.0 = No color (gray)
0.5 = Pastel
1.0 = Pure, vivid color

Brightness Values

0.0 = Black
0.5 = Medium
1.0 = Bright

1.11. HSB to RGB Conversion

The conversion algorithm (conceptual):

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

% Otherwise, convert via hue sectors
% (Implementation uses 6 sectors based on hue)

1.12. See Also

• sethsbcolor - Set HSB color

• currentrgbcolor - Get RGB color

• setrgbcolor - Set RGB color

• currentgray - Get gray value

• currentcmykcolor - Get CMYK color