Difference between revisions of "Generating a Code39 Barcode"
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Revision as of 12:53, 5 August 2010
The reason for writing this script was that I had already written a script for modifying a form we use, and on this form are barcodes, one of which indicates the type of form, but the other is variable according to the content of the page.
The script creates that custom part, which has a 10-digit number, then underneath is the barcode. By trial and error I determined that this was a Code39 barcode. Unfortunately, the barcode generator in Scribus cannot be scripted, and in fact you cannot make a custom size for the barcode, so I was copying the 10-digit number, then running Barcode generator, then resizing the created code, which is a PostScript creation, so when it's resized, the width of the bars may change. So far it's been Ok, but this might affect the scanning process.
So here is a first attempt, code39.py. I had thought it was rather slow, but rechecking shows acceptable speed on various computers. The first iterations would only generate a code for digits and uppercase letters (plus the start/stop character), but now it's complete.
Oh, Why Not?
Maybe I've Got It Done Now
|The final itch to scratch were those remaining characters, so now the Code 39 set is complete.
The python is a bit clumsy, but it works.
Somebody Please STOP Me!
#!/usr/bin/env python # -*- coding: utf-8 -*- # File: code39.py # Based on postnet2.py originally 2006.03.06 Gregory Pittman # this version 2010.08.04 # encodes numbers and letters, plus all other Code 39 characters """ Simple operation. First dialog asks for your code (numbers and uppercase letters, plus space, period, -,*,$,/,+,%) i.e., all characters allowed by Code 39, as many characters as you want. Second dialog asks for height of bars in points. Third dialog asks for the X-Pos and Y-Pos, separated only be whitespace, no comma! Fourth dialog confirms that you want to print the characters underneath. The start/stop character (*) is automatically added and does not show in the human-readable sequence. """ import scribus import sys # first the codes for numbers 0-9 code39 = ['nnswwn','wnsnnw','nwsnnw','wwsnnn','nnswnw','wnswnn','nwswnn','nnsnww','wnsnwn','nwsnwn'] # next add the codes for A-Z code39.extend(['wnnsnw','nwnsnw','wwnsnn','nnwsnw','wnwsnn','nwwsnn','nnnsww','wnnswn','nwnswn']) code39.extend(['nnwswn','wnnnsw','nwnnsw','wwnnsn','nnwnsw','wnwnsn','nwwnsn','nnnwsw','wnnwsn']) code39.extend(['nwnwsn','nnwwsn','wsnnnw','nswnnw','wswnnn','nsnwnw','wsnwnn','nswwnn']) # and these are for the rest code39.extend(['nswnwn','nsnsnsnn','nnsnsnsn','nsnnww','wsnnwn','nsnsnnsn','nsnnsnsn']) startstop = 'nsnwwn' narrow = 1.0 # narrow line width wide = 2.2 # wide line width b="Black" #line color if scribus.haveDoc(): S = scribus.valueDialog('Code 39','Enter Numbers or Uppercase Letters') height = scribus.valueDialog('Code 39','Enter Height of Bars (Points)') height = int(height) location = scribus.valueDialog('Code 39','Enter New X-Pos Y-Pos\n(No Comma, just space between)', '200 100') relpos = location.split() relx = int(relpos) rely = int(relpos) origx = relx humanread = scribus.valueDialog('Code 39','Print Human-Readable Code Too?\n(Any change means no)', 'Yes') scribus.setRedraw(1) scribus.setUnit(0) code = startstop for x in S[0:]: if x.isdigit(): xnum = int(x) code = code + code39[xnum] elif ((ord(x) > 64) and (ord(x) < 91)): # ord(character) yields the ascii value xnum = ord(x) - 55 code = code + code39[xnum] elif (ord(x) == 32): # space code = code + code39 elif ((ord(x) == 36) or (ord(x) == 37)): # $ and % xnum = ord(x) + 1 code = code + code39[xnum] elif ((ord(x) > 44) and (ord(x) < 48)): # - . / xnum = ord(x) - 6 code = code + code39[xnum] elif (ord(x) == 43): # + code = code + code39 elif (ord(x) == 42): code = code + startstop # * (adding for completeness) else: scribus.messageBox('OOPS!','Code 39 does not encode this character: ' + x,scribus.ICON_NONE,button1=scribus.BUTTON_OK) sys.exit(1) code = code + startstop for y in code[0:]: if y == 'n': relx = relx + narrow/2 d = scribus.createLine(relx,rely,relx,rely + height,) #narrow line scribus.setLineWidth(narrow, d) scribus.setLineColor(b, d) scribus.setFillColor(b, d) relx = relx + narrow + narrow/2 elif y == 'w': relx = relx + wide/2 d = scribus.createLine(relx,rely,relx,rely + height,) #wide line scribus.setLineWidth(wide, d) scribus.setLineColor(b, d) scribus.setFillColor(b, d) relx = relx + narrow + wide/2 elif y == 's': #for wide space relx = relx + wide if (humanread == 'Yes'): t = scribus.createText(origx, rely+height+3, relx - origx, 15) scribus.setText(S, t) scribus.setFont("DejaVu Sans Book", t) scribus.setFontSize(8, t) scribus.setTextAlignment(scribus.ALIGN_CENTERED, t) scribus.redrawAll() else: scribus.messageBox('OOPS!','You must have a document open to run this script',scribus.ICON_NONE,button1=scribus.BUTTON_OK) sys.ext(1)
Something worth mentioning here is that the precise position of the endpoints of lines is in the middle of the line. Thus, when I was creating lines of a particular width with very specific spacing in between, I had to account for the width of the lines or otherwise they would encroach on the space, and so you see these weird arithmetic additions in the if/elif loops.
Code 39 is a widely used code consisting of a series of narrow and wide black lines, alternating with narrow or wide white spaces. Each character is denoted by a sequence of 5 lines and 4 intervening spaces, with a narrow space in between characters. The digits 0-9 and capital letters A-Z, plus *, hyphen, period, $, /, % and space are defined. The * character is also known as the start/stop character, since all codes should begin and end with it to orient the scanner.
Narrow and wide lines, and narrow and wide spaces have corresponding width values, and the relative ratios are generally 1:2.2 to 1:3 (narrow:wide).