[Richard Suchenwirth] 2003-07-10 - [Barcode]s have ever and again fascinated me - I still can't read them, but I wanted to understand how things work, and that I often like to do with the help of [Tcl]. So here's my first take at generating Code 39 barcodes, which are a rather easy starter - you have bars and gaps in just two possible widths, and good documentation at e.g. http://www.barcodeisland.com/code39.phtml. Here's a result of the code below: [WikiDbImage test8252v.gif] I wrapped the crucial symbology in this proc, which builds tables of character values and bar-gap sequences, where 1 resp. 2 indicate the width. This results in two lists, which can be searched or indexed numerically, so I get three-way lookup functionality from two lists: ====== proc c39.tables {} { set chars {}; set patterns {} foreach {char pattern} { 0 111221211 1 211211112 2 112211112 3 212211111 4 111221112 5 211221111 6 112221111 7 111211212 8 211211211 9 112211211 A 211112112 B 112112112 C 212112111 D 111122112 E 211122111 F 112122111 G 111112212 H 211112211 I 112112211 J 111122211 K 211111122 L 112111122 M 212111121 N 111121122 O 211121121 P 112121121 Q 111111222 R 211111221 S 112111221 T 111121221 U 221111112 V 122111112 W 222111111 X 121121112 Y 221121111 Z 122121111 - 121111212 . 221111211 " " 122111211 $ 121212111 / 121211121 + 121112121 % 111212121 * 121121211 } {lappend chars $char; lappend patterns $pattern} list $chars $patterns } ====== One sees 9 parts in each symbol (5 bars, 4 gaps), of which three are wide and the rest narrow (hence the name "3 of 9" or 39. This part converts an input string into a bar-gap sequence, with added start and stop characters (both "*") and optionally a checksum character: ====== proc c39 {string {checksum ""}} { foreach {chars patterns} [c39.tables] break #-- blank out all undefined characters regsub -all {[^0-9A-Z.$/+%-]} [string toupper $string] " " string if {$checksum != ""} { set sum 0 foreach char [split $string ""] { incr sum [lsearch -exact $chars $char] } append string [lindex $chars [expr {$sum % 43}]] } set res "" foreach char [split *$string* ""] { append res [lindex $patterns [lsearch -exact $chars $char]] 1 } set res } ====== This renders a bar-gap sequence, as from the above code, into a photo image: ====== proc c39img {c39} { set width [expr {round([string length $c39]*5)}] set height 60 set im [image create photo -width $width -height $height] $im put white -to 0 0 $width $height set x 20 foreach {bar gap} [split $c39 ""] { set bar [expr {$bar == 1? 2: 6}] set gap [expr {$gap == 1? 5: 8}] $im put black -to $x 0 [expr {$x+$bar}] $height set x [expr {$x+$bar+$gap}] } set im } ====== Debugging tool, this re-translates a bar-gap sequence to [ASCII] characters: ====== proc c39read c39 { foreach {chars patterns} [c39.tables] break set res "" while {[string length $c39]} { set pattern [string range $c39 0 8] append res [lindex $chars [lsearch -exact $patterns $pattern]] set c39 [string range $c39 10 end] } set res } # Demo: set txt "ABCDE-12345" set bc [ c39 $txt ] set im [ c39img $bc ] label .l1 -anchor c -text $txt label .l2 -anchor c -image $im label .l3 -anchor c -text $bc pack .l1 .l2 .l3 ---- ====== [Eric Amundsen] May 16, 2005 Fixed the [encoding] for 'A'. In the doc that [Richard Suchenwirth] referenced the encoding for 'A' was the same as '9', this [http://www.adams1.com/39code.html] reference has the correct encoding for 'A'. Otherwise this code works great, tested with a real scanner even! ---- [HJG] Added some demo-code. ---- '''[IceAngel71] - 2015-09-22 00:17:54''' +++Ice Angel71 I have 11212211 and 112121211 and 21212111 But my code became a formula K(K+1)(K+2)/6K {39} which is saran wrap or base 3 Polymorphism <> Barcode | Arts and crafts of Tcl-Tk programming