Changes between Initial Version and Version 1 of Barcodes

Timestamp:

Jun 6, 2011, 6:46:55 AM (14 years ago)

Author:

tturner

Comment:

--

Barcodes

@@ +1 @@
+= Creating bitmap Barcodes in Django with the !ReportLab library =
+
+This describes a simple way to create dynamic bitmap Barcodes in Django.  
+
+!ReportLab's PDF library is well known, but less people are aware that it contains a
+mature graphics package able to create most kinds of business charts, as well as custom graphical widgets.
+
+= Installation =
+You will need the !ReportLab library from http://www.reportlab.com/
+
+Also make sure you have compiled the ''_rl_accel'' and ''_renderPM'' packages.  The latter
+is a sophisticated bitmap renderer with anti-aliasing, font handling and so on.
+!ReportLab's download page has a checker script to tell you what extensions
+are installed.
+
+= Creating a Barcode =
+The reportlab/graphics framework provides a Drawing object and many Shape objects,
+which include primitive shapes, and high-level objects like charts, barcodes and legends.  You
+can easily write your own too if you want to make dynamic bitmap buttons or fancy
+dashboard apps.
+
+The usual pattern we follow is to create a Drawing class with all of your widgets, 
+some sensible default data, and any visual settings you want.  Here is the example of a Code128 barcode however it would be easy to create a code39 Barcode etc.
+
+{{{
+#    mybarcode.py  
+from reportlab.graphics.shapes import Drawing, String
+from reportlab.graphics.charts.barcharts import HorizontalBarChart
+
+class MyBarcodeDrawing(Drawing):
+    def __init__(self, text_value, *args, **kw):
+        barcode = createBarcodeDrawing('Code128', value=text_value,  barHeight=10*mm, humanReadable=True)
+        Drawing.__init__(self,barcode.width,barcode.height,*args,**kw)       
+        self.add(barcode, name='barcode')
+        
+
+if __name__=='__main__':
+    #use the standard 'save' method to save barcode.gif, barcode.pdf etc
+    #for quick feedback while working.
+    MyBarcodeDrawing("HELLO WORLD").save(formats=['gif','pdf'],outDir='.',fnRoot='barcode')
+}}}
+
+
+Paste this into a file and execute it; you should get 4 chart files written to 
+disk in different formats.
+
+= Integrating into Django =
+
+Now we add a view to our ''views.py''.  This will examine the request
+for any dynamic parameters, since there's not much point serving
+a chart that doesn't vary.  We'll allow the user to pass in 4
+things as GET or POST parameters:  a title, a comma-separated list of numbers,
+and the overall width and height of the image.  Everything has a default in
+our Drawing class anyway, so we only pass through parameters which are
+present.
+
+You then ask the Drawing to render itself to your favourite bitmap format
+and generate a response with the right content-type
+
+{{{
+def barcode(request):
+    #instantiate a drawing object
+    import mybarcode
+    d = mybarcode.MyBarcodeDrawing("HELLO WORLD")
+    binaryStuff = d.asString('gif')
+    return HttpResponse(binaryStuff, 'image/gif')
+
+}}}
+
+Finally, you need a URL mapping.  In this case I have added this:
+
+{{{
+    (r'^barcode/$', 'myapp.views.barcode'),
+
+}}}
+
+Now you can start Django, point your browser at the URL with no arguments,
+and should see the barcode.  
+  http://localhost:8000/barcode/
+
+
+= Disclaimer =
+The author took this from the django [wiki:Charts] example. However he welcomes feedback.
+
+= Learning more about the chart library =
+The available chart types, widgets and properties are covered in the two
+Graphics manuals on this page.  Enjoy!
+   http://www.reportlab.org/os_documentation.html
+
+If you have questions about the barcodes rather than the Django integration, 
+ask on the reportlab-users list:
+  http://two.pairlist.net/mailman/listinfo/reportlab-users