重新实践《轻量级DJANGO》这本书

从手到尾，手写的DJANGO,不借助命令，效果一样的呢。

import os
import sys
import hashlib
from django.conf import settings

DEBUG = os.environ.get('DEBUG', 'on') == 'on'
SECRET_KEY = os.environ.get('SECRET_KEY', '%jv_4#hoaqwig2gu!eg#^ozptd*a@88u(aasv7z!7xt^5(*i&k')
ALLOWED_HOSTS = os.environ.get('ALLOWED_HOSTS', 'localhost').split(',')
BASE_DIR = os.path.dirname(__file__)

settings.configure(
    DEBUG=DEBUG,
    TEMPLATE_DEBUG = True,
    SECRET_KEY=SECRET_KEY,
    ALLOWED_HOSTS=ALLOWED_HOSTS,
    ROOT_URLCONF=__name__,
    MIDDLEWARE_CLASSES=(
        'django.middleware.common.CommonMiddleware',
        'django.middleware.csrf.CsrfViewMiddleware',
        'django.middleware.clickjacking.XFrameOptionsMiddleware',
    ),
    INSTALLED_APPS=(
        'django.contrib.staticfiles',
    ),
    TEMPLATES = [
        {
            'BACKEND': 'django.template.backends.django.DjangoTemplates',
            'DIRS': [
                os.path.join(BASE_DIR,'templates').replace('\\', '/'),
            ],
            'APP_DIRS': True,
        }
    ],
    STATICFILES_DIRS=(
        os.path.join(BASE_DIR, 'static'),
    ),
    STATIC_URL='/static/',
)

from django import forms
from django.conf.urls import url
from django.core.urlresolvers import reverse
from django.core.cache import cache
from django.core.wsgi import get_wsgi_application
from django.http import HttpResponse, HttpResponseBadRequest
from django.shortcuts import render
from django.views.decorators.http import etag
from io import BytesIO
from PIL import Image, ImageDraw

class ImageForm(forms.Form):
    height = forms.IntegerField(min_value=1, max_value=2000)
    width = forms.IntegerField(min_value=1, max_value=2000)

    def generate(self, image_format='PNG'):
        """Generate an image of the given type and return as raw bytes."""

        height = self.cleaned_data['height']
        width = self.cleaned_data['width']
        key = '{}.{}.{}'.format(width, height, image_format)
        content = cache.get(key)
        if content is None:
            image = Image.new('RGB', (width, height))
            draw = ImageDraw.Draw(image)
            text = '{} X {} demo'.format(width, height)
            textwidth, textheight = draw.textsize(text)
            if textwidth < width and textheight < height:
                texttop = (height - textheight) // 2
                textleft = (width - textwidth) // 2
                draw.text((textleft, texttop), text, fill=(255, 155, 5))
            content = BytesIO()
            image.save(content, image_format)
            content.seek(0)
            cache.set(key, content, 60 * 60)
        return content

def generate_etag(request, width, height):
    content = 'Placeholder: {0} x {1}'.format(width, height)
    return hashlib.sha1(content.encode('utf-8')).hexdigest()

@etag(generate_etag)
def placeholder(request, width, height):
    form = ImageForm({'height': height, 'width': width})
    if form.is_valid():
        image = form.generate()
        return HttpResponse(image, content_type='image/png')
    else:
        return HttpResponseBadRequest("Invalid Image Request")

def index(request):
    example = reverse('placeholder', kwargs={'width': 500, 'height': 500})
    print example, '#####################'
    context = {
        'example': request.build_absolute_uri(example)
    }
    print context, '@@@@@@@@@@@@@@@@@@@@@@@'
    return render(request, 'home.html', context)

urlpatterns = (
    url(r'^image/(?P<width>[0-9]+)x(?P<height>[0-9]+)/$', placeholder, name='placeholder'),
    url(r'^$', index, name='homepage'),
)

application = get_wsgi_application()

if __name__ == "__main__":
    from django.core.management import execute_from_command_line
    execute_from_command_line(sys.argv)