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  1. Overview • What is PostScript? • Types • Language Concepts • Control Operators • Examples

  2. What is PostScript • page description language : • PostScript is a programming language optimized for printing graphics and text • It was introduced by Adobe in 1985 • The main purpose of PostScript was to provide a convenient language in which to describe images in a device independent manner. This device independence means that the image is described without reference to any specific device features (e.g. printer resolution)

  3. Types • String: • “This is a string” would be written as (This is a string). • Express a string as hexadecimal codes in angle brackets. “ABC” would be expressed as <414243>. • Boolean • Real • Array

  4. Types • Arrays: • One Dimensional • Object of different types in an array • /arrayName [ 12 (Twelve) True] def • /arrayName [ 1 2 4 add] def • /arrayName 10 array • Store and Fetch array elements: put, get • /anArray 10 array def • anArray 8 (language) put • anArray 8 get

  5. Language Concepts • Variable: /varName value def • Path: A path is a collection of (possibly disjoint) line segments and curves arranged on the page. • newpath 144 72 moveto 144 432 linto stroke showpage • Dictionary: is a table that associates pairs of objects <Key, Value> • System Dictionary : operator , action • User Dictionary : /var1Name Value def

  6. Language Concepts • Procedures: • /inch {72 mul} def • Stack: • Graphic Stack • Operand Stack (clear, dup, pop, roll, pstack) • Dictionary Stack • Operator: Every command in PostScript is an operator: add, mul, findfont, moveto ...

  7. Programming in PostScript • Postfix Notation in PostScript : One must first place the operands on stack and then call the operator. • 5+27 5 27 add • 8 –7 * 3 8 7 3 mul sub 7 3 mul 8 exch sub

  8. Control Operators • Conditional: • Comparisons: • Logical Operator: • And , or, not, xor • bool { op } if • bool {op1} {op2} ifelse

  9. Control Operator • Loops: • Repeat: • Iteration { loop_body_expression} repeat • For: • Loop_counter_init_value increment_value {op} for • { op }loop : end with “exit” • AnArray {op} forall

  10. /Times-Italic findfont 30 scalefont setfont /printZip { 0 0 moveto (Zip) show} def 320 400 translate .95 -.05 0 % start incr. end {setgray printZip -1 .5 translate } for 1 setgray printZip showpage

  11. /starside { 72 0 lineto %add line to path currentpoint translate %move origin -144 rotate } def %rotate coord. sys. /star %stack: x y { moveto currentpoint translate 4 {starside} repeat closepath gsave .5 setgray fill grestore stroke } def 200 200 star

  12. Refrences • http://www-cdf.fnal.gov/offline/PostScript/BLUEBOOK.PDF • http://www.tailrecursive.org/postscript/postscript.html