IMGKit

Create JPGs using plain old HTML+CSS. Uses wkhtmltoimage on the backend which renders HTML using Webkit.

Heavily based on PDFKit.

Install

IMGKit

gem install imgkit

wkhtmltoimage

Usage

# IMGKit.new takes the HTML and any options for wkhtmltoimage
# run `wkhtmltoimage --extended-help` for a full list of options
kit = IMGKit.new(html, :quality => 50)
kit.stylesheets << '/path/to/css/file'

# Get the image BLOB
img = kit.to_img

# New in 1.3!
img = kit.to_img(:jpg)      #default
img = kit.to_img(:jpeg)     
img = kit.to_img(:png)
img = kit.to_img(:tif)
img = kit.to_img(:tiff)

# Save the image to a file
file = kit.to_file('/path/to/save/file.jpg')
file = kit.to_file('/path/to/save/file.png')

# IMGKit.new can optionally accept a URL or a File.
# Stylesheets can not be added when source is provided as a URL of File.
kit = IMGKit.new('http://google.com')
kit = IMGKit.new(File.new('/path/to/html'))

# Add any kind of option through meta tags
IMGKit.new('<html><head><meta name="imgkit-quality" content="75"...

# Format shortcuts - New in 1.3!
IMGKit.new("hello").to_jpg       
IMGKit.new("hello").to_jpeg      
IMGKit.new("hello").to_png       
IMGKit.new("hello").to_tif       
IMGKit.new("hello").to_tiff

Configuration

If you're on Windows or you installed wkhtmltoimage by hand to a location other than /usr/local/bin you will need to tell IMGKit where the binary is. You can configure IMGKit like so:

# config/initializers/imgkit.rb
IMGKit.configure do |config|
  config.wkhtmltoimage = '/path/to/wkhtmltoimage'
  config.default_options = {
    :quality => 60
  }
  config.default_format = :png
end

Rails

Mime Types

register a .jpg mime type in: 

#config/initializers/mime_type.rb
Mime::Type.register       "image/jpeg", :jpg

register a .png mime type in: 

#config/initializers/mime_type.rb
Mime::Type.register       "image/png", :png

Controller Actions

You can respond in a controller with:

@kit = IMGKit.new(render_as_string)

format.jpg do
  send_data(@kit.to_jpg, :type => "image/jpeg", :disposition => 'inline')
end

- or -

format.png do
  send_data(@kit.to_png, :type => "image/png", :disposition => 'inline')
end

- or -

respond_to do |format|
  send_data(@kit.to_img(format.to_sym), 
            :type => "image/png", :disposition => 'inline')
end

This allows you to take advantage of rails page caching so you only generate the image when you need to.

--user-style-sheet workaround

To overcome the lack of support for --user-style-sheet option by wkhtmltoimage 0.10.0 rc2 as reported here http://code.google.com/p/wkhtmltopdf/issues/detail?id=387

  require 'imgkit'
  require 'restclient'
  require 'stringio'

  url = 'http://domain/path/to/stylesheet.css'
  css = StringIO.new( RestClient.get(url) )

  kit = IMGKit.new(<<EOD)
  <!DOCTYPE HTML>
  <html lang="en">
  <head>
    <meta charset="UTF-8">
    <title>coolest converter</title>
  </head>
  <body>
    <div class="cool">image kit</div>
  </body>
  </html>
  EOD

  kit.stylesheets << css

Note on Patches/Pull Requests

  • Fork the project.
  • Setup your development environment with: gem install bundler; bundle install
  • Make your feature addition or bug fix.
  • Add tests for it. This is important so I don't break it in a future version unintentionally.
  • Commit, do not mess with rakefile, version, or history. (if you want to have your own version, that is fine but bump version in a commit by itself I can ignore when I pull)
  • Send me a pull request. Bonus points for topic branches.

Copyright (c) 2010 Chris Continanza Based on work by Jared Pace
See LICENSE for details.