载波：如何裁剪和调整大小以使最终图片的宽度和高度完全相同？

我正在将Rails 3与载波和Rmagick一起使用。我希望将图片的大小精确调整为192 x 135，一开始这个接缝很简单，但是直到现在我都没有尝试过。

有人找到解决方案了吗？这是我给上传者的代码。

class AvatarUploader < CarrierWave::Uploader::Base

   #Include RMagick or MiniMagick support:
  include CarrierWave::RMagick
  include CarrierWave::MiniMagick

  # Choose what kind of storage to use for this uploader:
  storage :file
  # storage :fog

  def store_dir
    "uploads/#{model.class.to_s.underscore}/#{mounted_as}/#{model.id}"
  end


  # Provide a default URL as a default if there hasn't been a file uploaded:
   def default_url
  #   # For Rails 3.1+ asset pipeline compatibility:
   ActionController::Base.helpers.asset_path("fallback/" + [version_name, "default.png"].compact.join('_'))
  #
  #   "/images/fallback/" + [version_name, "default.png"].compact.join('_')
   end
  process :resize_to_fit => [250, 250]


  # Process files as they are uploaded:
  # process :scale => [200, 300]
  #
  # def scale(width, height)
  #   # do something
  # end

  # Create different versions of your uploaded files:
   version :thumb do
     process :resize_to_fit => [200, 200]
   end

   version :medium do
       process :resize_to_fit => [250, 250]
    end

    version :mini do
        process :resize_to_fit => [100, nil]
        process crop: '100x100+0+0'
     end

     version :grid do
         process :resize_to_fit => [192, 135]
         process crop: '192x135+0+0'
      end

  # Add a white list of extensions which are allowed to be uploaded.
  # For images you might use something like this:
  # def extension_white_list
  #   %w(jpg jpeg gif png)
  # end

  # Override the filename of the uploaded files:
  # Avoid using model.id or version_name here, see uploader/store.rb for details.
  # def filename
  #   "something.jpg" if original_filename
  # end

  private

    # Simplest way
    def crop(geometry)
      manipulate! do |img|      
        img.crop(geometry)
        img
      end    
    end

    # Resize and crop square from Center
    def resize_and_crop(size)  
      manipulate! do |image|                 
        if image[:width] < image[:height]
          remove = ((image[:height] - image[:width])/2).round 
          image.shave("0x#{remove}") 
        elsif image[:width] > image[:height] 
          remove = ((image[:width] - image[:height])/2).round
          image.shave("#{remove}x0")
        end
        image.resize("#{size}x#{size}")
        image
      end
    end

end