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Catalog / PostScript Cheatsheet

PostScript Cheatsheet

A quick reference guide to the PostScript page description language, covering fundamental concepts, operators, and syntax for generating graphics and text.

Core Concepts

Stack Operations

PostScript is a stack-based language. Most operators take their arguments from the stack and place their results back onto the stack.

  • push - Places an operand on the stack.
  • pop - Removes the top operand from the stack.
  • exch - Exchanges the top two operands on the stack.
  • dup - Duplicates the top operand.
  • clear - Empties the stack.

Example:

1 2 3  % pushes 1, 2, and 3 onto the stack

Data Types

  • integer

Whole numbers (e.g., 1, -10, 0).
  • real

Floating-point numbers (e.g., 3.14, -0.5).
  • boolean

true or false.
  • string

Sequence of characters enclosed in parentheses (e.g., (Hello, world!)).
  • array

Ordered collection of objects enclosed in square brackets (e.g., [1 2 3]).
  • dictionary

Collection of key-value pairs.

Variables and Procedures

  • define - Associates a name with a value or procedure.
  • Variables are declared using /name value def.
  • Procedures are defined using { ... } def.

Example:

/myvar 10 def  % Defines a variable named myvar with value 10
/square {dup mul} def % Defines a procedure named square
myvar square % calls procedure

Graphics Operations

Path Construction

  • newpath

Starts a new path.
  • moveto

Moves the current point to (x, y). Usage: x y moveto.
  • lineto

Draws a line from the current point to (x, y). Usage: x y lineto.
  • curveto

Draws a Bezier curve. Usage: x1 y1 x2 y2 x3 y3 curveto (control points 1 & 2, endpoint 3).
  • closepath

Closes the current path by drawing a line to the starting point.

Drawing and Filling

  • stroke

Draws a line along the current path.
  • fill

Fills the area enclosed by the current path.
  • eofill

Fills the path using the even-odd rule.

Color and Line Attributes

  • setrgbcolor - Sets the current color using RGB values. Usage: red green blue setrgbcolor (values between 0 and 1).
  • setgray - Sets the current color using a grayscale value. Usage: gray setgray (value between 0 and 1).
  • setlinewidth - Sets the line width. Usage: width setlinewidth.
  • setlinecap - Sets the line cap style (0 = butt, 1 = round, 2 = square).
  • setlinejoin - Sets the line join style (0 = miter, 1 = round, 2 = bevel).

Example:

0.5 0.2 0.8 setrgbcolor % sets the color to a shade of purple
2 setlinewidth % sets line width to 2 points

Text Operations

Font Handling

  • findfont

Loads a font. Usage: (FontName) findfont.
  • scalefont

Scales the font. Usage: font size scalefont.
  • setfont

Sets the current font. Usage: font setfont.

Text Display

  • show

Displays a string at the current position. Usage: (text) show.
  • stringwidth

Calculates the width of a string. Returns width and height. Usage: (text) stringwidth.
  • showpage

Displays the current page and resets the graphics state.

Text Positioning

Text positioning is done via moveto. Ensure a font is set before displaying text.

Example:

/Helvetica findfont 12 scalefont setfont
100 500 moveto
(Hello, PostScript!) show

Control Structures

Conditional Statements

  • if

Executes a code block if a condition is true. Usage: boolean {code} if.
  • ifelse

Executes one code block if a condition is true, and another if false. Usage: boolean {true_code} {false_code} ifelse.

Looping

  • repeat

Executes a code block a specified number of times. Usage: count {code} repeat.
  • loop

Executes a code block indefinitely until explicitly stopped with exit.
  • for

Executes a code block for a range of values. Usage: initial increment limit {code} for.

Example 

/n 5 def
0 1 n {
  dup mul  % Square the number
  ==       % Print the squared value
} for

This example calculates and prints the square of numbers from 1 to 5.
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