phantom-snap 0.0.18.1

phantom-snap
====

Render HTML to an image using PhantomJS with this library designed to scale for high volume continuous operation.

Features
--------

- Provides full timing control around the rendering process.
- Maintains a live PhantomJS process (instead of a new one per request which many wrappers do, which is slow).
- Render content from a URL, or provide the HTML content directly to the renderer

Roadmap
-------
- Decorator to manage rendering under specified timezones
- Decorator to manage rendering under specified proxies.

Examples
--------

The example assumes you have http://phantomjs.org/ installed.


This first example demonstrates rendering a URL and saving the resulting image to a file at /tmp/google-render.jpg.
::

from phantom_snap.settings import PHANTOMJS
from phantom_snap.phantom import PhantomJSRenderer
from phantom_snap.imagetools import save_image

config = {
'executable': '/usr/local/bin/phantomjs',
'args': PHANTOMJS['args'] + ['--disk-cache=false', '--load-images=true'],
'env': {'TZ': 'America/Los_Angeles'}
'timeouts': {
'page_load': 3
}
}
r = PhantomJSRenderer(config)

url = 'http://www.google.com'

try:
page = r.render(url, img_format='JPEG')
save_image('/tmp/google-render', page)
finally:
r.shutdown(15)

A sample response from ``r.render(url)`` looks like this:

::

{
"status": "success",
"format": "PNG",
"url": "http://www.google.com",
"paint_time": 141,
"base64": "iVBORw0KGgo <SNIP> RK5CYII=",
"error": null,
"load_time": 342
}

This example shows how to provide HTML content directly to the rendering process, instead of requesting it.
::

from phantom_snap.settings import PHANTOMJS
from phantom_snap.phantom import PhantomJSRenderer
from phantom_snap.imagetools import save_image

config = {
'executable': '/usr/local/bin/phantomjs',
'args': PHANTOMJS['args'] + ['--disk-cache=false', '--load-images=true']
}
r = PhantomJSRenderer(config)

url = 'http://www.a-url.com'
html = '<html><body>Boo ya!</body></html>'

try:
page = r.render(url=url, html=html, img_format='PNG')
save_image('/tmp/html-render', page)
finally:
r.shutdown(15)

If you would like to offload the running of phantomjs into `AWS Lambda <https://aws.amazon.com/lambda/>`_, you can use the ``LambdaRenderer`` class in the following way:

::

from phantom_snap.lambda_renderer import LambdaRenderer
from phantom_snap.imagetools import save_image

config = {
'url': 'http://url-to-my-lambda-func',
}

r = LambdaRenderer(config)
url = 'http://www.youtube.com'

page = r.render(url, img_format='JPEG')
save_image('/tmp/youtube-render', page)

r.shutdown()

To learn more about offloading renders into AWS Lambda, please see the ``serverless`` folder.


Decorators
----------

**Lifetime**

If you plan on running a ``PhantomJSRenderer`` instance for an extended period of time with high volume, it's recommended that you wrap the instance with a ``Lifetime`` decorator as shown below.

The ``Lifetime`` decorator will transparently shutdown the underlying PhantomJS process if the renderer is idle or after a maximum lifetime to release any accumulated resources. This is important if PhantomJS is configured to use a memory-based browser cache to prevent the cache from growing too large. After the ``Lifetime`` decorator shuts down the Renderer (due to idle time or maximum time) the next render request will automatically create a new PhantomJS process.

::

from phantom_snap.settings import PHANTOMJS
from phantom_snap.phantom import PhantomJSRenderer
from phantom_snap.decorators import Lifetime

config = {
'executable': '/usr/local/bin/phantomjs',
'args': PHANTOMJS['args'] + ['--disk-cache=false', '--load-images=true'],
'env': {'TZ': 'America/Los_Angeles'},

# Properties for the Lifetime decorator
'idle_shutdown_sec': 900, # 15 minutes, Shutdown PhantomJS if it's been idle this long
'max_lifetime_sec': 43200 # 12 hours, Restart PhantomJS every 12 hours
}

r = Lifetime(PhantomJSRenderer(config))

try:
urls = [] # Some endless source of URL targets

for url in urls:
page = r.render(url=url, img_format='JPEG')

# Store the image somewhere

finally:
r.shutdown()


You can view the default configuration values in ``phantom_snap.settings.py``.