Today I found something cool for drawing graphs. Its called GraphViz, You can download it from

http://www.graphviz.org/

It can output in various formats including SVG, PNG and GIF. But PNG and GIF dont have aliasing enabled, so they are pretty crappy.

For an example, look here. An image generated using PNG output

http://www.linkulu.com/random/?format=png&numnodes=10&size=5,5

Now look @ an another random graph with SVG output

http://www.linkulu.com/random/?format=svg&numnodes=10&size=5,5

Here is the python code to generate the graphs. I used Django ofcourse

def randomGraph(request):
   #Defaults for Generating random graphs
   random.seed()
   numnodes=5
   format="svg"
   size="2,2"
   mime="image/svg+xml"
 
 
   if "format" in request.GET:
       infor=request.GET["format"]
       if(infor=="png"):
           mime="image/png"
           format="png"
         
       elif(infor=="gif"):
           mime="image/gif"
           format="gif"
         
   if "size" in request.GET:
       size=request.GET["size"]
 
 
   if "numnodes" in request.GET:
       numnodes=int(request.GET["numnodes"])
 
 
   dot="""digraph G{
       size ="%s";
       orientation=portrait;
       {{{dot}}}
   }""" % (size)
 
   nodes=[]
   shapes=['ellipse','box','circle','record','triangle','doublecircle']
   styles=['bold','dotted','normal']
   colors=['cadetblue2','dimgray','dodgerblue1','beige','aliceblue','ghostwhite',
                   'greenyellow','hotpink4','lightgoldenrod2']
 
   st=""
   for i in range(numnodes):
       nodes.append("a"+str(i));
 
   for node in nodes:
       s1=random.randint(0,len(shapes)-1)
       c1=random.randint(0,len(colors)-1)
       st=st+" %s [shape=%s fillcolor=%s style=filled];\n" %(node,shapes[s1],colors[c1])
 
   for i in range(numnodes):
       r1=random.randint(0,numnodes-1)
       r2=random.randint(0,numnodes-1)
       s2=random.randint(0,len(styles)-1)
       st=st+nodes[r1]+"->"+nodes[r2]+" [style=%s];\n" %(styles[s2])
 
   dot=dot.replace("{{{dot}}}",st)
 
   tmpout, filename = mkstemp()
 
   pobj=Popen('dot -T%s -o %s' % (format,filename),shell=True,stdin=PIPE,stdout=PIPE)
 
   fin = pobj.stdin
   fout = pobj.stdout
   fin.write(dot)
   fin.flush()
   fin.close()
   pobj.wait()
 
   fout = os.fdopen(tmpout, 'r')
   jpeg = fout.read()
   fout.close()
 
   os.remove(filename)
 
   #jpeg=dot
 
   return HttpResponse(content=jpeg, mimetype='%s' % (mime))

Labels: graphviz python