使用Carrierwave调整条件图像大小
我需要有条件地创建不同版本的上传图像。 我知道Carrierwave支持这个function。 但我的要求有点棘手。
对于每个上传的图像，我需要创建2个版本，并需要根据条件缩放原始图像。
下面的代码将让您更好地了解我要做的事情：
version :leftright, :if => :image? do process :resize_to_fill => [667*2, 778*2] ,:if => :is_retina_resolution? process :resize_to_fill => [667, 778] ,:if => !:is_retina_resolution? end version :updown, :if => :image? do process :resize_to_fill => [1024*2, 487*2] ,:if => :is_retina_resolution? process :resize_to_fill => [1024, 487] ,:if => !:is_retina_resolution? end #resize the original image process :resize_to_fill => [1024*2, 768*2] ,:if => :is_retina_resolution? process :resize_to_fill => [1024, 768] ,:if => !:is_retina_resolution? def is_retina_resolution?(new_file) image = MiniMagick::Image.open(new_file.file) true if image[:height] >= 1536 and image[:width] >= 2048 end 显然这不起作用。 Carrierwave抛出此错误：
Errno::ENOENT - No such file or directory - #
我尝试了另一种变化：
version :leftright, :if => :image? do if :is_retina_resolution? process :resize_to_fill => [667*2, 778*2] else process :resize_to_fill => [667, 778] end end version :updown, :if => :image? do if :is_retina_resolution? process :resize_to_fill => [1024*2, 487*2] else process :resize_to_fill => [1024, 487] end end def is_retina_resolution?(new_file) image = MiniMagick::Image.open(new_file) true if image[:height] >= 1536 and image[:width] >= 2048 end
这不会引发任何错误。 但它总是以retina size生成图像（第一个条件）
所以我尝试了另外一个变体：
version :leftright, :if => :image? && :is_retina_resolution do process :resize_to_fill => [667*2, 778*2] end version :leftright, :if => :image? && !:is_retina_resolution do process :resize_to_fill => [667, 778] end version :updown, :if => :image? && :is_retina_resolution do process :resize_to_fill => [1024*2, 487*2] end version :updown, :if => :image? && !:is_retina_resolution do process :resize_to_fill => [1024, 487] end
这不会抛出任何错误，也不会创建任何版本。
有人可以帮我吗？
更新：
基于@DMKE的建议，我做了这个改动，现在它工作正常
version :leftright, :if => :image? do process :resize_to_fill => [667*2, 778*2] ,:if => :is_retina_resolution? process :resize_to_fill => [667, 778] ,:if => :is_not_retina_resolution? end version :updown, :if => :image? do process :resize_to_fill => [1024*2, 487*2] ,:if => :is_retina_resolution? process :resize_to_fill => [1024, 487] ,:if => :is_not_retina_resolution? end #resize the original image process :resize_to_fill => [1024*2, 768*2] ,:if => :image_and_retina? process :resize_to_fill => [1024, 768] ,:if => :image_and_not_retina? process :if => :not_image? def image_and_retina?(img) is_img = image? img return false unless is_img return is_retina_resolution?(img) end def image_and_not_retina?(img) is_img = image? img return false unless is_img return !is_retina_resolution?(img) end # returns true if image file def image?(new_file) self.file.content_type.include? 'image' end def not_image?(new_file) !self.file.content_type.include? 'image' end def is_retina_resolution?(new_file) image = MiniMagick::Image.open(self.file.file) true if image[:height] >= 1536 and image[:width] >= 2048 end def is_not_retina_resolution?(new_file) image = MiniMagick::Image.open(self.file.file) true if image[:height] < 1536 and image[:width] < 2048 end
虽然不是语法错误，但此代码有一个语义缺陷：
version :updown, :if => :image? && !:is_retina_resolution do # ... end
在这里， :image? && !:is_retina_resolution :image? && !:is_retina_resolution 总是求值为false（在IRb终端中尝试!:foo ），因此永远不会创建:updown版本。 对于process foo: [sx,sy], if: !:bar?同样的解释process foo: [sx,sy], if: !:bar?
由于CarrierWave不支持:unless选项（据我所知），实现目标的唯一方法是CarrierWave::Uploader::Base子类中的一些方法定义：
process resize_to_fill: [667*2, 778*2], if: :image_and_retina? process resize_to_fill: [667, 778], if: :image_and_not_retina? def image_and_retina?(img) image?(img) && is_retina_resolution(img) end def image_and_not_retina?(img) image?(img) && !is_retina_resolution(img) end