Table of Contents

• 1. currentgray
  • 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 State Preservation
    • 1.6.2. Adaptive Rendering
    • 1.6.3. Color Space Detection
    • 1.6.4. Monochrome Validation
  • 1.7. Common Pitfalls
  • 1.8. Error Conditions
  • 1.9. Implementation Notes
  • 1.10. Color Conversion Formulas
  • 1.11. See Also

1. currentgray

Returns current color as gray value.

1.1. Syntax

– currentgray → num

1.2. Stack Effects

Table 1. Before

Level	Object
(empty)	–

Table 2. After

Level	Object
0	num (0.0 = black to 1.0 = white)

1.3. Description

currentgray returns the gray value of the current color parameter in the graphics state.

• If the current color space is DeviceGray, currentgray returns the color value most recently specified to setgray or [setcolor].

• If the current color space is DeviceRGB or DeviceCMYK, currentgray converts the current color to a gray value using standard conversion formulas.

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

The returned value is always in the range 0.0 (black) to 1.0 (white).

1.4. PostScript Level

Level 1 and later

1.5. Examples

Querying current gray

0.5 setgray
currentgray
% Stack: 0.5

Converting from RGB

1 0 0 setrgbcolor  % Red
currentgray
% Stack: 0.3 (approximate gray equivalent)

Saving and restoring gray

currentgray        % Save current
/savedGray exch def

0 setgray          % Change to black
drawShape

savedGray setgray  % Restore

Conditional drawing based on color

currentgray 0.5 lt {
  % Current color is dark
  drawWithWhiteOutline
} {
  % Current color is light
  drawWithBlackOutline
} ifelse

1.6. Common Use Cases

1.6.1. Color State Preservation

/DrawWithTemporaryGray {
  % Save current gray
  currentgray

  % Draw with specific gray
  0.7 setgray
  drawElement

  % Restore
  setgray
} def

1.6.2. Adaptive Rendering

/DrawAdaptive {
  currentgray
  dup 0.5 lt {
    % Dark color - use light decorations
    pop
    1 setgray
    drawDecorations
  } {
    % Light color - use dark decorations
    pop
    0 setgray
    drawDecorations
  } ifelse
} def

1.6.3. Color Space Detection

/IsGrayColorSpace {
  currentgray
  0.5 setgray
  currentgray 0.5 eq
  % If true, was already in DeviceGray
} def

1.6.4. Monochrome Validation

/EnsureGrayscale {
  currentgray setgray  % Force to gray
} def

1.7. Common Pitfalls

Color Space Conversion - Conversion from RGB/CMYK to gray may lose color information.

1 0 0 setrgbcolor  % Red
currentgray        % ~0.3
setgray            % Now gray, not red

Returns 0.0 for Unknown Spaces - Pattern and other color spaces return black.

/Pattern setcolorspace
myPattern setcolor
currentgray        % Returns 0.0

Approximate Conversion - RGB/CMYK to gray conversion is approximate.

0.5 0.5 0.5 setrgbcolor
currentgray
% May not be exactly 0.5 due to conversion

Use for Monochrome Output - Good for ensuring grayscale rendering.

1.8. Error Conditions

Error	Condition
[stackoverflow]	No room on operand stack

1.9. Implementation Notes

• Very fast query operation

• No modification to graphics state

• Always returns value in range 0.0 to 1.0

• Conversion formulas are device-independent

• Level 1 operator (widely supported)

1.10. Color Conversion Formulas

When converting from other color spaces:

RGB to Gray

gray = 0.3 × red + 0.59 × green + 0.11 × blue

CMYK to Gray (approximate)

gray = 1 - min(1, 0.3×cyan + 0.59×magenta + 0.11×yellow + black)

Other Spaces

gray = 0.0

1.11. See Also

• setgray - Set gray color

• currentrgbcolor - Get RGB color

• currentcmykcolor - Get CMYK color (Level 2)

• currenthsbcolor - Get HSB color