carrierwave

CarrierWave::RMagick#manipulate!

Manipulate the image with RMagick. This method will load up an image
and then pass each of its frames to the supplied block. It will then
save the image to disk.

=== Gotcha

This method assumes that the object responds to +current_path+.
Any class that this module is mixed into must have a +current_path+ method.
CarrierWave::Uploader does, so you won't need to worry about this in
most cases.

=== Yields

[Magick::Image] manipulations to perform
[Integer] Frame index if the image contains multiple frames
[Hash] options, see below

=== Options

The options argument to this method is also yielded as the third
block argument.

Currently, the following options are defined:

==== :write
A hash of assignments to be evaluated in the block given to the RMagick write call.

An example:

     manipulate! do |img, index, options|
       options[:write] = {
         :quality => 50,
         :depth => 8
       }
       img
     end

This will translate to the following RMagick::Image#write call:

    image.write do |img|
      self.quality = 50
      self.depth = 8
    end

==== :read
A hash of assignments to be given to the RMagick read call.

The options available are identical to those for write, but are passed in directly, like this:

    manipulate! :read => { :density => 300 }

==== :format
Specify the output format. If unset, the filename extension is used to determine the format.

=== Raises

[CarrierWave::ProcessingError] if manipulation failed.

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