帶載波調整大小的條件圖像

Question

我需要有條件地創建不同版本的上傳圖像。我知道Carrierwave支持這個功能。但我的要求有點棘手。

對於每個上傳的圖片，我需要創建2個版本，並需要根據條件縮放原始圖像。

下面的代碼會給你更好的主意，我想做的事：

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 

顯然，這是行不通的。 Carrierwave拋出這個錯誤：

Errno::ENOENT - No such file or directory - #<ActionDispatch::Http::UploadedFile:0xe41d508>

我試過另一種變化：

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 

這不會引發任何錯誤。但它總是在retina size（第一狀態）生成圖像

於是，我就多了一個變化：

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 

，這並不拋出任何錯誤，也不會創建任何版本。

有人可以幫我嗎？

更新：

基於由@DMKE的建議，我做了這個變化，現在它工作正常

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 

Answer 1

雖然不是語法錯誤，這段代碼有一個語義缺陷：

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

這裏，:image? && !:is_retina_resolution總是評估爲false（在IRb終端中嘗試!:foo），因此:updown版本是從不創建。同樣的解釋也適用於process foo: [sx,sy], if: !:bar?

由於CarrierWave不支持:unless選項（據我可以告訴），來實現自己的目標的唯一方法是在你的CarrierWave::Uploader::Base子類中的一些方法定義：

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