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phancap - website screenshot service

Web service (API) to create website screenshots.

Self-hosted and written in PHP. Caching included.

phancap is useful for:

Features

  • Configurable browser size
  • Configurable screenshot size
  • Clip and full page rendering (full height)
  • JPG, PNG and PDF output (PDFs are searchable)
  • Authentication
  • Can run on a normal web server without GUI. See dependencies.

Note

phancap does not rely on a "real" browser. Currently cutycapt is utilized, which uses a pretty bare webkit to render the pages. Do not expect pixel-for-pixel identical rendering as your desktop browser.

Getting started

Basic setup

  1. Download the .phar file and put it onto your web server
  2. Open the phar file in your browser
  3. Click the "setup check" link
  4. Fix all errors that are reported
  5. Run phancap.phar/get.php?url=cweiske.de and see the screenshot

Advanced setup

With the basic setup, everyone may use your server to create website screenshots. You may want to change that or simply change some default settings.

  1. Create a config file phancap.phar.config.php
  2. Edit it; see the configuration options.

URL parameters

get.php supports the following parameters:

Browser parameters

url
Website URL
bwidth
Browser width (default: 1024)
bheight
Browser height (default: none)

Screenshot parameters

swidth
Screenshot width (default: none (no scaling))
sheight
Screenshot height (default: none)
sformat
Screenshot format (png, jpg, pdf, default: png)
smode
Screenshot mode (screen (4:3) or page (full website height))
smaxage

Maximum age of screenshot in seconds. ISO 8601 duration specifications accepted:

  • P1Y - 1 year
  • P2W - 2 weeks
  • P1D - 1 day
  • PT4H - 4 hours

The configuration file defines a minimum age that the user cannot undercut ($screenshotMinAge), as well as a default value ($screenshotMaxAge).

Authentication parameters

atimestamp
Time at which the request URL was generated (unix timestamp)
atoken
Access token (username)
asignature
Signature for the request. See the authentication section.

Configuration

phancap looks at several places for its configuration file:

  1. phancap.phar.config.php in the same directory as your phancap.phar file.
  2. /etc/phancap.php

Configuration variables

$cacheDir
Full file system path to image cache directory
$cacheDirUrl
Full URL to cache directory
$access

Credentials for access control

true to allow access to anyone, false to disable it completely. array of username - secret key combinations otherwise.

$disableSetup
Disable setup.php which will leak file system paths
$redirect
Redirect to static image urls after generating them
$timestampmaxAge
How long a signature timestamp is considered valid. 2 days default.
$screenshotMaxAge

Cache time of downloaded screenshots.

When the file is as older than this, it gets re-created.

$screenshotMinAge

Minimum age of a screeshot. 1 hour default.

A user cannot set the max age parameter below it.

Authentication

Creating screenshots of websites is a resource intensive process. To prevent unauthorized access to the service, phancap supports authentication via a signature parameter similar to OAuth's oauth_signature.

Phancap's configuration file may contain a $access variable:

true
Everyone is allowed to access the service
false
Nobody is allowed to access the service
array

A list of usernames that are allowed to request screenshots, together with their secret keys (password):

$access = array(
   'user1' => 'secret1',
   'user2' => 'secret2',
)

The signature algorithm is as follows:

  1. Parameters atimestamp (current unix timestamp) and atoken (username) have to be added to the URL parameters
  2. URL parameters are normalized as described in OAuth Parameters Normalization:
    1. Sort parameters list by name
    2. Name and value are raw-url-encoded
    3. Name and value are concatenated with = as separator
    4. The resulting strings are concatenated with & as separator
  3. URL parameter string is used together with the secret key to create a HMAC-SHA1 digest
  4. Digest is appended to the URL as asignature

Example

Note

The docs/ directory contains an example PHP client implementation.

We want to create a screenshot of http://example.org/ in size 400x300, using the browser size of 1024x768:

http://example.org/phancap/get.php?swidth=400&sheight=300&url=http%3A%2F%2Fexample.org%2F&bwidth=1024&bheight=768

Phancap's config file contains:

$access = array(
    'user' => 'secret'
);

Our parameters are thus:

Name Value
swidth 400
sheight 300
url http://example.org/
bwidth 1024
bheight 768

At first, we need to add parameters atimestamp and atoken. atimestamp is the current unix timestamp. atoken is our user name: user.

Now the parameter list is sorted:

Name Value
atimestamp 1396353987
atoken user
bheight 768
bwidth 1024
sheight 300
swidth 400
url http://example.org/

The parameters are raw-url-encoded. The only value that changes is the url, it becomes http%3A%2F%2Fexample.org%2F.

Concatenating the name/value pairs leads to the following string:

atimestamp=1396353987&atoken=user&bheight=768&bwidth=1024&sheight=300&swidth=400&url=http%3A%2F%2Fexample.org%2F

Creating the HMAC digest with sha1, the calculated string and our key secret gives us the following string:

9a12eac5ff859f9306eaaf5a18b9a931fe10b89d

This is the signature; it gets appended to the URL as asignature parameter.

Dependencies

  • External tools:
  • Libraries (already included in the .phar):
    • PEAR's System.php

License

phancap is licensed under the AGPL v3 or later.

Author

Written by Christian Weiske, cweiske@cweiske.de

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