裁切指定尺寸大小图片

resize_and_crop.rb

def crop_image_fixed_size(file, file_width, file_height)
  begin
    image = MiniMagick::Image.new(file)
    original_width,original_height = image[:width],image[:height]
    if original_width*file_height != original_height*file_width
      if original_width*file_height >= original_height*file_width
        original_height_clone = original_height
        original_width_clone = original_height_clone * (file_width.to_f / file_height)
      elsif original_width*file_height <= original_height * file_width
        original_width_clone = original_width
        original_height_clone = original_width_clone * (file_height.to_f / file_width)
      end
    else
      original_height_clone = original_height
      original_width_clone = original_width
    end
    if original_width_clone != original_width || original_height_clone != original_height
      x = ((original_width - original_width_clone)/2).round
      y = ((original_height - original_height_clone)/2).round
      image.crop("#{original_width_clone}x#{original_height_clone}+#{x}+#{y}")
    end
  rescue MiniMagick::Error
    flash[:errors] = "我的水平不高，这张图片可能我没办法处理，请换一张"
    redirect back
  rescue MiniMagick::Invalid
    flash[:errors] = "你很坏，你上传的文件很可能不是一张图片！"
    redirect back
  else
    image.resize("#{file_width}x#{file_height}")
    return image
  end
end