Module ActionView::Helpers::ImageMagickMacroHelper
In: actionpack/lib/action_view/helpers/image_magick_macro_helper.rb

Provides helpers for using ImageMagick. These helpers rely on the corresponding ImageMagick macro in the controller. See ActionController::Macros::ImageMagick::ClassMethods

You can use the following ImageMagick commands with this helper: (see imagemagick.org/script/command-line-options.php for a description of what they do).

  • resize(100x100), aliases s and geometry
  • blur(1.0,1.0), alias blur_image
  • crop(10,10,30,30)
  • colorize(0.5,0.5,0.5,ffff00)
  • equalize
  • flip
  • flop
  • implode(2.0)
  • level(0.3,0.1)
  • normalize
  • oilpaint(2.0)
  • opaque(ffffff,ffff00)
  • posterize(10)
  • sharpen(0.2,0.3)
  • rotate(45)
  • border(10,10,ffff00)
  • trim

And, as a special service to Rails users, this extension has a method that is not available for ImageMagick, but can be very useful:

  • part(100x100), will give you a part of the image with exactly the given proportions (in this case, 100x100 pixels). The original image will be resized to match either the required width or height, depending on the aspect ratio. The image is then centered and the left and right, or top and bottom, slack is cut off. Thus, part will always give you an image of the same size.

You can also define and use your own ‘recipes’. See the documentation for ActionController::Macros::ImageMagick::RecipeSet

Methods

imagemagick_path   imagemagick_tag  

Public Instance methods

imagemagick_path(filename_or_params, commands = [], options = {})

Returns the path for the image, which will be rendered with the given ImageMagick commands.

filename_or_params and commands works the same as for imagemagick_tag. options does nothing.

imagemagick_tag(filename_or_params, commands = nil, options = {})

The workings of this function depend on how you enabled the imagemagick extension: as a separate action, or as an after_filter for your own action.

As an action

Returns an image tag for the image with the given +filename, which will be rendered with the given ImageMagick commands.

filename_or_params should point to an image in the directory you specified with imagemagick_for. You can have subdirectories, in that case you prepend the name of the subdirectory to filename_or_params

commands can be a String of commands, separated by plus signs: 

   "resize(100x100)+flop+rotate(45)"

or, commands can be an Array of command strings and command+argument arrays: 

   [ ["resize", "100x100"], "flop", ["rotate", "45"] ]

The options will be forwarded to the normal image_tag method (and will be used as the html attributes.) The only exception is this option:

:controller:the name of the controller in which the ImageMagick macro is activated. It defaults to the current controller, but you can specify something else.

Examples: 

   <%= imagemagick_tag "presentation.png", "resize(100x100)+flop", :alt=>"Presentation" %>
   <%= imagemagick_tag "presentation.png", "equalize", :controller=>"photo", :alt=>"Presentation" %>
   <%= imagemagick_tag "presentation.png", "equalize" %>
   <%= imagemagick_tag "rails/presentation.png", "equalize" %>

As an after_filter

Returns an image tag for the action with the parameters in filename_or_params (in url_form format). The result of that action will be rendered with the given ImageMagick commands.

filename_or_params should be the url_for options hash that points to the action that renders the image. You can use any parameters your action need.

commands can be a String of commands, separated by plus signs: 

   "resize(100x100)+flop+rotate(45)"

or, commands can be an Array of command strings and command+argument arrays: 

   [ ["resize", "100x100"], "flop", ["rotate", "45"] ]

The options will be forwarded to the normal image_tag method (and will be used as the html attributes.)

Instead of provinding a separate commands argument, you can also specify the commands as the :commands parameters in the url_for hash. (If you have renamed :commands in the configuration, you should use the new name instead.)

Examples: 

   <%= imagemagick_tag({:action=>'display_image', :id=>10}, 'resize(100x100)+flop', {:alt=>"Presentation"}) %>
   <%= imagemagick_tag({:controller=>'photo', :action=>'display_image', :id=>10}, 'resize(100x100)+flop', {:alt=>"Presentation"}) %>
   <%= imagemagick_tag :action=>'display_image', :id=>10, :user=>10, :other_param=>'abc', :commands=>'equalize' %>

[Validate]