Imagemagick code behind http://www.urban.org/urban-wire/first-step-toward-breaking-homelessness-jail-cycle

build_graphic.py

import csv
import json
import subprocess


jData = []
remap = {"Custodial Arrest":"custodial","NonCustodial Arrest":"noncustodial","Contact":"contact"}
cr = csv.reader(open("data/source_data.csv",'rU'))


#Reformat source csv
head = cr.next()
iData = {}
for row in cr:
  person = int(row[2])
  offense = remap[row[0]]
  date = int(row[1])
  if(str(row[3]) != ''):
    los = int(row[3])
  else:
    los = -99

  if person not in iData:
    iData[person] = ["none"]*91
  iData[person][date] = offense
  if(los != -99):
    for i in range(date+1, date+1+los):
      try:
        iData[person][i] = "jail"
      except IndexError:
        break


for person in iData:
  obj = {"id": person}
  obj["vals"] = iData[person]
  jData.append(obj)

with open("graphic_data.json","w") as f:
  json.dump(jData, f)


VALS = {"none":("(245,245,245)", "#f5f5f5", "srgb(245,245,245)"), "contact":("(22,150,210)", "#1696d2", "srgb(22,150,210)"), "custodial":("(85,183,72)", "#55b748", "srgb(85,183,72)"),"jail":("(253,191,17)", "#fdbf11", "srgb(253,191,17)"),"noncustodial":("(6,38,53)", " #062635", "srgb(6,38,53)")}

with open('graphic_data.txt', 'w') as f:
#write a .txt file which Imagemagick can convert to a png (a pixel map)
#Specify the dimensions and color space (1 color gets a 3x3 square of pixels, for sharper images)
  f.write("# ImageMagick pixel enumeration: 273,1602,255,srgb\n")
  for o in jData:
    row = int(o["id"])
    for i in range(0, len(o["vals"])):
      v = o["vals"][i]
      cols = VALS[v]
# 0,0: (251, 255, 255)  #fbffff  srgb(251, 255, 255)
      for j in range(0,9):
        R = i*3
        C = row*3
        tups = [(R, C),(R,C+1),(R,C+2),(R+1,C),(R+1,C+1),(R+1,C+2),(R+2,C),(R+2,C+1),(R+2,C+2)]
        f.write("%i,%i:  %s  %s  %s\n"%(tups[j][0], tups[j][1], cols[0], cols[1], cols[2]))

subprocess.call(["convert","graphic_data.txt","graphic.png"])