Table of Contents

• 1. currentmatrix
  • 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. Preserving Transformation State
    • 1.6.2. Analyzing Current Transformation
    • 1.6.3. Building on Current Transformation
    • 1.6.4. Coordinate Space Conversion
  • 1.7. Common Pitfalls
  • 1.8. Error Conditions
  • 1.9. Implementation Notes
  • 1.10. Matrix Interpretation
  • 1.11. Extracting Transformation Components
  • 1.12. Performance Considerations
  • 1.13. Relationship to Graphics State
  • 1.14. See Also

1. currentmatrix

Gets the current transformation matrix from the graphics state.

1.1. Syntax

matrix currentmatrix → matrix

1.2. Stack Effects

Table 1. Before

Level	Object
0	matrix (array)

Table 2. After

Level	Object
0	matrix (modified array)

1.3. Description

currentmatrix replaces the value of matrix with the current transformation matrix (CTM) from the graphics state and pushes the modified matrix back on the operand stack.

The CTM defines the transformation from user space coordinates to device space coordinates. It is modified by transformation operators like translate, scale, rotate, and concat.

1.4. PostScript Level

Level 1 and later

1.5. Examples

Getting the CTM

matrix currentmatrix  % Get current transformation
% → e.g., [2 0 0 2 100 100]

Saving and restoring CTM

matrix currentmatrix  % Save CTM
/savedCTM exch def

% ... perform transformations ...

savedCTM setmatrix    % Restore CTM

Examining transformations

100 100 translate
2 2 scale
45 rotate
matrix currentmatrix
% Shows combined transformation matrix

1.6. Common Use Cases

1.6.1. Preserving Transformation State

% Better than gsave/grestore when you only need CTM
matrix currentmatrix
/savedMatrix exch def

% Complex transformations
100 200 translate
3 1.5 scale

% Restore
savedMatrix setmatrix

1.6.2. Analyzing Current Transformation

% Check current scale
matrix currentmatrix
dup 0 get  % a component (x-scale)
exch 3 get % d component (y-scale)
% Now have x and y scale factors on stack

1.6.3. Building on Current Transformation

% Get current, modify, apply
matrix currentmatrix
45 rotate  % Modify matrix
concat     % Apply modified matrix

1.6.4. Coordinate Space Conversion

% Get CTM for manual coordinate transformation
/ctm matrix currentmatrix def
% Use with transform operator

1.7. Common Pitfalls

Modifies Input Array - currentmatrix modifies the array you provide.

/m [0 0 0 0 0 0] def
m currentmatrix pop
% m now contains CTM, original values lost

Not a Copy - The returned array is the one you provided, not a new array.

matrix currentmatrix
dup setmatrix
% Both stack entries refer to same array

Use with gsave/grestore - For complete state saving, use gsave/grestore:

% Only saves CTM:
matrix currentmatrix /saved exch def
% ... transformations ...
saved setmatrix

% Saves entire graphics state:
gsave
% ... transformations ...
grestore

Reuse Arrays - For efficiency, reuse matrix arrays:

/workMatrix 6 array def
% Reuse many times:
workMatrix currentmatrix ...
workMatrix currentmatrix ...

1.8. Error Conditions

Error	Condition
[rangecheck]	Array has fewer than 6 elements
[stackunderflow]	No operand on stack
[typecheck]	Operand is not an array

1.9. Implementation Notes

• The CTM is stored internally in device space

• Very large transformations may experience precision loss

• The CTM is part of the graphics state

• Modified by gsave/grestore

• The array must have at least 6 elements

1.10. Matrix Interpretation

The returned matrix [a b c d tx ty] transforms coordinates:

x_device = a×x_user + c×y_user + tx
y_device = b×x_user + d×y_user + ty

Components represent:

• a, d: scaling in x and y

• b, c: rotation/shearing

• tx, ty: translation

1.11. Extracting Transformation Components

% Get translation
matrix currentmatrix
dup 4 get /tx exch def
5 get /ty exch def

% Get scale (assuming no rotation)
matrix currentmatrix
dup 0 get /sx exch def
3 get /sy exch def

% Get rotation (assuming uniform scale)
matrix currentmatrix
dup 1 get exch 0 get
atan /angle exch def

1.12. Performance Considerations

• Very fast operation

• No matrix computation required

• Just copies 6 values from graphics state

• Reusing arrays avoids allocation overhead

1.13. Relationship to Graphics State

The CTM is modified by:

• translate

• scale

• rotate

• concat

• setmatrix

• initmatrix

• gsave/grestore

1.14. See Also

• setmatrix - Set the CTM

• defaultmatrix - Get device default matrix

• initmatrix - Reset CTM to default

• concat - Concatenate matrix with CTM

• transform - Transform coordinates by CTM

• gsave - Save graphics state

• grestore - Restore graphics state