ImageMagick

Either require 'dragonfly/rails/images' or Dragonfly[:images].configure_with(:imagemagick) gives us an ImageMagick Processor, Encoder, Analyser and Generator.

Given a Job object

image = app.fetch('some/uid')

...OR a Dragonfly model accessor...

image = @album.cover_image

we have the following:

Shortcuts

image.thumb('40x30')              # same as image.process(:thumb, '40x30')
image.jpg                         # same as image.encode(:jpg)
image.png                         # same as image.encode(:png)
image.gif                         # same as image.encode(:gif)
image.strip                       # same as image.process(:strip)
image.convert('-scale 30x30')     # same as image.process(:convert, '-scale 30x30')

thumb and convert can optionally take a format (e.g. :gif) as the second argument. Bang methods like image.thumb!('40x30'), image.png! etc. will operate on self.

Below are some examples of geometry strings for thumb:

'400x300'            # resize, maintain aspect ratio
'400x300!'           # force resize, don't maintain aspect ratio
'400x'               # resize width, maintain aspect ratio
'x300'               # resize height, maintain aspect ratio
'400x300>'           # resize only if the image is larger than this
'400x300<'           # resize only if the image is smaller than this
'50x50%'             # resize width and height to 50%
'400x300^'           # resize width, height to minimum 400,300, maintain aspect ratio
'[email protected]'              # resize so max area in pixels is 2000
'400x300#'           # resize, crop if necessary to maintain aspect ratio (centre gravity)
'400x300#ne'         # as above, north-east gravity
'400x300se'          # crop, with south-east gravity
'400x300+50+100'     # crop from the point 50,100 with width, height 400,300

Processor

image.process(:crop, :width => 40, :height => 50, :x => 20, :y => 30)
image.process(:crop, :width => 40, :height => 50, :gravity => 'ne')

image.process(:flip)                         # flips it vertically
image.process(:flop)                         # flips it horizontally

image.process(:greyscale, :depth => 128)     # default depth 256

image.process(:resize, '40x40')
image.process(:resize_and_crop, :width => 40, :height=> 50, :gravity => 'ne')

image.process(:rotate, 45, :background_colour => 'transparent')   # default bg black

The method thumb takes a geometry string and calls resize, resize_and_crop or crop accordingly.

image.process(:thumb, '400x300')             # calls resize

Encoder

The ImageMagick Encoder gives us:

image.encode(:jpg)
image.encode(:gif)
image.encode(:png)
image.encode(:tiff)

and various other formats (see ImageMagick Encoder).

You can also pass additional options to the imagemagick command line:

image.encode(:jpg, '-quality 10')

Analyser

The ImageMagick Analyser gives us these methods:

image.width               # => 280
image.height              # => 355
image.aspect_ratio        # => 0.788732394366197
image.portrait?           # => true
image.landscape?          # => false
image.depth               # => 8
image.number_of_colours   # => 34703
image.format              # => :png
image.image?              # => true - will return true or false for any content

Generator

The ImageMagick Generator gives us these methods:

image = app.generate(:plain, 600, 400, 'rgba(40,200,30,0.5)')
image = app.generate(:plain, 600, 400, '#ccc', :format => :gif)
                                                    # generate a 600x400 plain image
                                                    # any css-style colour should work

image = app.generate(:plasma, 600, 400, :gif)       # generate a 600x400 plasma image
                                                    # last arg defaults to :png

image = app.generate(:text, "Hello there")          # an image of the text "Hello there"

image = app.generate(:text, "Hello there",
  :font_size => 30,                                 # defaults to 12
  :font_family => 'Monaco',
  :stroke_color => '#ddd',
  :color => 'red',
  :font_style => 'italic',
  :font_stretch => 'expanded',
  :font_weight => 'bold',
  :padding => '30 20 10',
  :background_color => '#efefef',                   # defaults to transparent
  :format => :gif                                   # defaults to png
)

Note that the text generation options requires ghostscript (gs) to be installed.

Options are meant to resemble css as much as possible. You can also use, for example, 'font-family' instead of :font_family.

You can use padding-top, padding-left, etc., as well as the standard css shortcuts for padding (it assumes unit is px).

An alternative for :font_family is :font (see the imagemagick docs), which could be a complete filename. Available fonts are those available on your system.

Configuration

There are some options that can be set, e.g. if the imagemagick convert command can't be found:

app.configure do |c|
  c.convert_command = "/opt/local/bin/convert"          # defaults to "convert"
  c.identify_command = "/opt/local/bin/identify"        # defaults to "identify"
  c.log_commands = true                                 # defaults to false
end