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

libvips

If you run into trouble installing libvips with Ruby introspection on Linux, follow the build steps here. Please note the importance of gobject-introspection and libgirepository1.0-dev plus the export GI_TYPELIB_PATH=/usr/local/lib/girepository-1.0/ and ldconfig.

Dependencies

The vips library and its dependencies.

Usage

Configure your app the usual way:

Dragonfly.app.configure do
  plugin :libvips
end

Supported Formats

List of supported formats (based on your build and version of the libvips library) is available as:

DragonflyLibvips::SUPPORTED_FORMATS # => ["csv", "dz", "gif", …]
DragonflyLibvips::SUPPORTED_OUTPUT_FORMATS # => ["csv", "dz", "gif", …]

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')

Extract Area

Extract an area from an image.

image.extract_area(x, y, width, height)

Rotate

Rotate a number of degrees with

image.rotate(90)

Options

All processors support input_options and output_options for passing additional options to vips. For example:

image.encode('jpg', output_options: { Q: 50 })
image.encode('jpg', output_options: { interlace: true }) # use interlace to generate a progressive jpg
pdf.encode('jpg', input_options: { page: 0, dpi: 600 })

Defaults:

input_options: { access: :sequential }
output_options: { profile: … } # embeds 'sRGB_v4_ICC_preference.icc' profile included with this gem

Analysers

The following methods are provided

image.width # => 280
image.height # => 355
image.xres # => 72.0
image.yres # => 72.0
image.progressive # => true
image.aspect_ratio # => 0.788732394366197
image.portrait? # => true
image.landscape? # => false
image.format # => 'png'
image.image? # => true

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.