AppEngine upload, combine images and save to blob store. Python PIL and PIL paste function to give uploaded image a background

image_to_blobstore.py

# -*- coding: utf-8 -*-

"""
    A real simple app for using webapp2 with auth and session.

    It just covers the basics. Creating a user, login, logout
    and a decorator for protecting certain handlers.

    Routes are setup in routes.py and added in main.py
"""
# standard library imports
from __future__ import with_statement

import logging
import re
import json
import urllib
import datetime
import hashlib
import uuid
import os
import StringIO

# related third party imports
import webapp2
import httpagentparser
from webapp2_extras import security
from webapp2_extras.auth import InvalidAuthIdError, InvalidPasswordError
from webapp2_extras.i18n import gettext as _
from webapp2_extras.appengine.auth.models import Unique
from google.appengine.api import urlfetch
from google.appengine.api import taskqueue
from google.appengine.api import app_identity
from google.appengine.api import app_identity
from google.appengine.ext import blobstore
from google.appengine.ext.webapp import blobstore_handlers
from google.appengine.api import images
from PIL import Image

# local application/library specific imports
import models
import forms as forms
from lib.basehandler import BaseHandler

from google.appengine.ext import ndb

from dateutil.relativedelta import relativedelta

from app import base_config


from google.appengine.api import files


class HelloWorldHandler(BaseHandler):

    def get(self):
        
        templateData = {
            'upload_path' : blobstore.create_upload_url('/upload-test')
        }
        return self.render_template("/uploadtest.html", **templateData)
        
        # data = {
        #     'status' : 'OK',
        #     'form_post_url' : blobstore.create_upload_url('/upload-test')
        # }
        # return sendJSONresponse(self.response, data, self.request.GET.get('callback'))


class UploadTestHandler(blobstore_handlers.BlobstoreUploadHandler):

    def post(self):

        uploaded_image = self.get_uploads('image') # 'image' is the file form field name

        if len(uploaded_image) == 1:

            # upload profile
            blob_info = uploaded_image[0]
            if blob_info.size > 0:
                
                logging.info(blob_info)

                image_url = images.get_serving_url(blob_info.key(), size=None, crop=False, secure_url=None)
                
                image_w_bg = addBackground(blob_info.key())
                
                # self.response.headers['Content-Type'] = "image/png"
                # self.response.out.write(image_w_bg)

                if image_w_bg:
                    
                    # Create the file
                    file_name = files.blobstore.create(mime_type='application/octet-stream')

                    # Open the file and write to it
                    with files.open(file_name, 'a') as f:
                      f.write(image_w_bg) #image_w_bg.tostring('raw'))

                    # Finalize the file. Do this before attempting to read it.
                    files.finalize(file_name)

                    # Get the file's blob key
                    new_blob_key = files.blobstore.get_blob_key(file_name)
                    
                    output = images.get_serving_url(new_blob_key, size=None, crop=False, secure_url=None)
                    logging.info("$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$")
                    logging.info(output)

                self.redirect(str(output))

            else:
                # no image uploaded, must delete the blob that was allocated by GAE #weirdappenginething
                blob_info.delete()
                logging.info("deleting blob")

                return self.response.write("no image uploaded")
            
'''adds a white background 1400x900'''
def addBackground(blob_key):

    # try:
    blob_reader = blobstore.BlobReader(blob_key)
    img = Image.open(blob_reader)
    
    logging.info("inside addBackground")
    logging.info(img)
    logging.info("******************************************")

    img_w,img_h=img.size
    background = Image.new('RGBA', (1440,900), (255, 255, 255, 255))
    bg_w,bg_h=background.size
    offset=((bg_w-img_w)/2,(bg_h-img_h)/2)
    background.paste(img,offset)
    
    output = StringIO.StringIO()
    background.save(output, format="png")
    background_data = output.getvalue()
    output.close()

    return background_data

    # except:
    #     logging.error("unable to out 'img' passed into addBackground")
    #     return None


def sendJSONresponse(response, data, callback, httpcode=200):
    jsonp_callback = callback

    if jsonp_callback:
        response.headers['Content-Type'] = 'application/javascript'
        response_data = jsonp_callback + "(" + json.dumps(data) + ")"

    else:
        response.headers['Content-Type'] = 'application/json'
        response_data = json.dumps(data)

    response.status = httpcode

    return response.write(response_data)