CarrierWave 图片上传和图片特殊处理

使用 CarrierWave 这个 gem 来完成图片上传和使用 mini_magick 这个 gem 来处理上传的图片

这是我之前的一篇文章，觉得蛮好的，现在把它放到这里来。

1. CarrierWave

1.1 安装

gem 'carrierwave'

1.2 生成 uploader

$ rails generate uploader Avatar

# 这是生成的文件
app/uploaders/avatar_uploader.rb

1.3 添加图片的字段

rails g migration add_image_to_articles image:string

image 存储是文件名

1.4 挂载那个 uploader

class Article < ActiveRecord::Base
  attr_accessible :content, :title, :image, :remote_image_url
  mount_uploader :image, AvatarUploader
end

1.5 给表单加上图片上传的域

<div class="field">
  <%= f.label :image %><br />
  <%= f.file_field :image %>
  <%= f.hidden_field :image_cache %>
</div>

1.6 引用上传的图片地址

# app/views/articles/show.html.erb
<%= image_tag @article.image_url.to_s %>

这样就可以上传图片了,默认图片是存储在 public 那个文件夹中

1.7 远程图片

# app/views/articles/show.html.erb
<div class="field">
  <%= f.label :remote_image_url, "or image URL" %>
  <%= f.text_field :remote_image_url %>
</div>

2. MiniMagick 处理图片

2.1 安装

gem 'mini_magick'

# app/uploaders/avatar_uploader.rb
include CarrierWave::MiniMagick

2.2 裁减图片

# app/uploaders/avatar_uploader.rb
version :thumb do
 process :resize_to_limit => [200, 200]
end

# app/views/articles/show.html.erb
<%= image_tag @article.image_url(:thumb).to_s %>

2.3 增加模糊

# app/uploaders/avatar_uploader.rb
# radial_blur为模糊的程度
process :radial_blur => 2
def radial_blur(amount)
  manipulate! do |img|
    img.radial_blur(amount)
    img = yield(img) if block_given?
    img
  end
end

2.4 旋转

process :sample_rotate => ["90%", "-80>"]
def sample_rotate(sample, rotate)
  manipulate! do |img|
    img.combine_options do |c|
      c.sample(sample)
      c.rotate(rotate)
    end
    img = yield(img) if block_given?
    img
  end
end

2.5 加水印

process :make_watermark => "你的图片的地址"
def make_watermark(watermark)
  manipulate! do |img|
    img = img.composite(MiniMagick::Image.open(watermark, "jpg")) do |c|
      c.gravity "SouthEast"
    end
    img = yield(img) if block_given?
    img
  end
end

打水印的位置可以是'Center', 'NorthWest', 'North', 'NorthEast', 'West', 'Center', 'East', 'SouthWest', 'South', 'SouthEast'

2.6 转化格式

process :convert => 'png'

def filename
  super.chomp(File.extname(super)) + '.png' if original_filename.present?
end

更多的用法可以看这里https://github.com/carrierwaveuploader/carrierwave/blob/master/lib/carrierwave/processing/mini_magick.rb

完结。