回形针水印处理器无法识别选项`-crop'错误

Question

尝试通过paperclip和imagemagick为图像添加水印。这是我的水印处理器的要点： https://gist.github.com/xamenrax/6164246

我的模特是：

  CONVERT_OPTION_PREFIX = "-background transparent -compose Copy -gravity center -extent"

  has_attached_file :image,
            :processors => [:watermark],
            :styles => {
              :slider => { geometry: "480x226#", watermark_path: "#{Rails.root}/public/images/watermarks/medium/watermark.png" },
              :big => { geometry: "670x426#", watermark_path: "#{Rails.root}/public/images/watermarks/big/watermark.png" },
              :medium => { geometry: "155x160#", watermark_path: "#{Rails.root}/public/images/watermarks/thumb/watermark.png" },
              :thumb => { geometry: "106x160#", watermark_path: "#{Rails.root}/public/images/watermarks/thumb/watermark.png" },
              :wide_medium => { geometry: "220x150#", watermark_path: "#{Rails.root}/public/images/watermarks/thumb/watermark.png" },
              :square => { geometry: "100x102#", watermark_path: "#{Rails.root}/public/images/watermarks/square/watermark.png" }
            },
            convert_options: { slider: "#{CONVERT_OPTION_PREFIX} 480x226", big: "#{CONVERT_OPTION_PREFIX} 670x426", medium: "#{CONVERT_OPTION_PREFIX} 155x160", wide_medium: "#{CONVERT_OPTION_PREFIX} 220x150", square: "#{CONVERT_OPTION_PREFIX} 100x102"  }

但是在保存图片时我会收到错误：

Command 'composite -gravity SouthEast '/Users/xamenrax/projects/handmadefood/public/images/watermarks/medium/watermark.png' '/var/folders/26/0fjt3lc101x1714cc5xxkfgc0000gn/T/pro20130806-1681-i05d3l20130806-1681-1yvw0r1' -resize '480x' -crop '480x226+0+127' +repage '/var/folders/26/0fjt3lc101x1714cc5xxkfgc0000gn/T/pro20130806-1681-i05d3l20130806-1681-1yvw0r1'' returned 1. Expected 0

有什么问题？ -crop '480x226+0+127'无效选项？