Dragonfly libvips

Dragonfly analysers and processors for libvips image processing library

From the libvips README:

libvips is a 2D image processing library. Compared to similar libraries, libvips runs quickly and uses little memory. libvips is licensed under the LGPL 2.1+.

Installation

Add this line to your application's Gemfile:

gem 'dragonfly_libvips'

And then execute:

$ bundle

Or install it yourself as:

$ gem install dragonfly_libvips

Dependencies

The vips library and its dependencies.

Usage

Configure your app the usual way:

Dragonfly.app.configure do
  plugin :libvips
end

Processors

Thumb

Create a thumbnail by resizing/cropping

image.thumb('40x30')

Below are some examples of geometry strings for thumb:

'400x300' # resize, maintain aspect ratio
'400x' # resize width, maintain aspect ratio
'x300' # resize height, maintain aspect ratio
'400x300<' # resize only if the image is smaller than this
'400x300>' # resize only if the image is larger than this

Encode

Change the encoding with

image.encode('jpg')

optionally pass output arguments (specific to format)

image.encode('jpg', 'Q=50')

Rotate

Rotate a number of degrees with

image.rotate(90)

Vips

Perform an arbitrary vips command

image.vips('resize', '0.5', { 'input_args' => 'page=2', 'output_args' => 'Q=50', 'format' => 'jpg' })

corresponds to the command-line

vips resize <original_path>[page=2] <new_path>[Q=50] 0.5

Vipsthumbnail

Perform an arbitrary vipsthumbnail command

image.vipsthumbnail('--size=100x100', { 'input_args' => 'page=2', 'output_args' => 'Q=50', 'format' => 'jpg' })

corresponds to the command-line

vipsthumbnail  <original_path>[page=2] --size=100x100 -o <new-path>[Q=50]

Analysers

The following methods are provided

image.width # => 280
image.height # => 355
image.aspect_ratio # => 0.788732394366197
image.portrait? # => true
image.landscape? # => false
image.format # => 'png'
image.image? # => true

Configuration

Dragonfly.app.configure do
  plugin :libvips,
          vips_command: "/opt/local/bin/vips" # defaults to "vips"
          vipsheader_command: "/opt/local/bin/vipsheader" # defaults to "vipsheader"
          vipsthumbnail_command: "/opt/local/bin/vipsthumbnail" # defaults to "vipsthumbnail"
end

Acknowledgements

This plugin, its structure, sample files, tests as well as this README are based on the original Dragonfly's ImageMagick plugin by Mark Evans.

Development

After checking out the repo, run bin/setup to install dependencies. Then, run rake test to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and tags, and push the .gem file to rubygems.org.

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/tomasc/dragonfly_libvips.

License

The gem is available as open source under the terms of the MIT License.