User:Eleanorg/1.3/Dissolute Image/Code2

create an image file

This script grabs an unadopted pixel randomly from the DB, creates an image file on the fly and gives it to the user. It also creates a hash for that file to ensure that users can't tamper with it.
#!/usr/bin/python
#-*- coding:utf-8 -*-
 
import cgi
import cgitb; cgitb.enable()
import hashlib
import os
import pymongo, random  
from pymongo import Connection
 
## grab a random unadopted pixel from the database and create an image out of it

connection = Connection()
myDB = connection['pixelDbQuery1']
collection = myDB.collection

##--------- choose pixel randomly from DB ------------#
# 
# find all entries where url is empty:
unadopted = []
for entry in collection.find({"url": ""}):
    unadopted.append(entry)			# add this pixel's hash as an item to the 'unadopted' dictionary
#print unadopted
 
howMany = len(unadopted)			# find out how many items in 'unadopted' list
#print howMany
random = random.randint(0,howMany)		# pick a random number in this range
#print random
pixelHash = unadopted[random]			# ...and choose the pixel at this index
#print pixelHash

#color = "#333"
#xpos = str(10)
#ypos = str(20)
pixelId = pixelHash['ID']
color = pixelHash['color']
xpos = pixelHash['xpos']
ypos = pixelHash['ypos']
image = "../../forbiddenPixels/images/" + xpos + "_" + ypos + ".jpg"
#print image

#--------- create an image with it ------------#

# creates new image and saves to images folder
command = "convert -size 1x1 xc:" + color + " " + image   
#print command	           	
os.popen(command, 'r').read()


#--------- create hash for img and put in DB ------------#
 
# md5sum -- create an hex digest of a file's md5 hash
# usage: print md5sum(open('tmp.html','rb'))

#def md5sum(f, block_size=8192):
#    md5 = hashlib.md5()
#    while True:
#        data = f.read(block_size)
#        if not data:
#            break
#        md5.update(data)
#    return md5.hexdigest()

## test:
## print md5sum(open('tmp.html','rb'))

# define hashing function
def md5sum(f, block_size=8192):
    md5 = hashlib.md5()
    while True:
        data = f.read(block_size)
        if not data:
            break
        md5.update(data)
    return md5.hexdigest()

# run hashing function, assigning to var 'hash'
pixelHash = md5sum(open(image,'rb'))
# insert hash for this pixel into its array in DB
collection.update( {"ID": pixelId}, {"$set":{"hash": pixelHash}})

#--------- give user link to the image ------------#
 
htmlHeader = """<!DOCTYPE html>
<html>
  <head>
    <title>Adopt a Pixel</title>
        <link <link rel="stylesheet" href="">
  </head>
  <body>"""
 
 
print "Content-Type: text/html"
print 
print htmlHeader
print """
<h1>the DISSOLUTE IMAGE</h1>
Right click & 'save as' to download your pixel: <br />

<a href=" """ + image + """ ">Download Pixel</a>
<br />
The hash is """ + pixelHash + """
</body>
</html>"""