使用Carrierwave调整条件图像大小

问题描述

我需要有条件地创建不同版本的上传图片。我知道Carrierwave支持这个功能。但我的要求有点棘手。

I need to create different versions of uploaded image conditionally. I know Carrierwave supports this feature. But my requirements are a bit tricky.

对于每个上传的图像，我需要创建2个版本，需要根据条件缩放原始图像。

For each uploaded image I need to create 2 versions and need to scale the original image based on conditions.

下面的代码可以让您更好地了解我要做的事情：

Below code will give you better idea what I am trying to do:

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：

Apparently this is not working. Carrierwave throws this error:

Errno :: ENOENT - 没有这样的文件或目录 - ＃< ActionDispatch :: Http :: UploadedFile：0xe41d508>

我尝试了另一种变体：

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。但它始终以视网膜大小生成图像（第一个条件）

This doesn't throw any error. But it always generates the image in retina size (1st condition)

所以我尝试了另外一个变体：

So I tried one more variation:

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

这不会引发任何错误，也不会创建任何版本。

This doesnt throw any error and also not created any version.

有人可以帮助我吗？

更新：

根据@DMKE的建议，我做了这个改动，现在工作正常

Based on the suggestion by @DMKE, I made this changes, now it works fine

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

推荐答案

虽然不是语法错误，此代码有一个语义缺陷：

Although not a syntax error, this code has a semantical flaw:

version :updown, :if => :image? && !:is_retina_resolution  do
  # ...
end

此处，：形象？ &安培;&安培; ！：is_retina_resolution 始终评估为false（在IRb终端中尝试！：foo ），因此：updown 版本从不创建。同样的解释适用于进程foo：[sx，sy]，如果：！：bar？

Here, :image? && !:is_retina_resolution always evaluates to false (try !:foo in an IRb terminal), thus the :updown version is never created. The same explanation goes for process foo: [sx,sy], if: !:bar?

自CarrierWave不支持：除非选项（据我所知），实现目标的唯一方法是 CarrierWave中的一些方法定义： ：Uploader :: Base 子类：

Since CarrierWave does not support an :unless option (as far as I can tell), the only way to achieve your goal are some method definitions in your CarrierWave::Uploader::Base subclass:

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

这篇关于使用Carrierwave调整条件图像大小的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！