学步园

1.添加gem

gem 'carrierwave', '0.6.2'
gem 'mini_magick' #不使用rmagick，占内存

如果之前没安装magickimage 就运行sudo apt-get install imagemagick

magickimage主要功能是切割图片

2.bundle install
3.为users表添加一个avatar字段,也可以为其他名称，注意相应的代码修改，如果users表本身有一个字段保存图片的路径，可不新加avatar字段

rails g migration add_avatar_to_users avatar:string   
rake db:migrate
4.生成Avatar，跟你添加的字段相同
rails generate uploader Avatar #将会生成文件app/uploaders/avatar_uploader.rb
5.为user的model user.rb添加如下代码，使表之间关联
mount_uploader :avatar, AvatarUploader

6.接下来进行修改app/uploaders/avatar_uploader.rb，下面是一个例子
# encoding: utf-8


class AvatarUploader < CarrierWave::Uploader::Base

  include CarrierWave::MiniMagick #使用minimagick处理压缩图片，确保安装magickimage这个东东，ubuntu可以sudo apt-get install magickimage

  # Choose what kind of storage to use for this uploader: 

  storage :file

  # storage :fog

  # Override the directory where uploaded files will be stored.

  # This is a sensible default for uploaders that are meant to be mounted:

  def store_dir  #定义上传到哪个文件夹下

    "#{Rails.root}/public/site_data/#{model.site_id}"

  end

  def filename  #图片保存的名字 这里已解决上存相同名字图片覆盖问题

     "#{secure_token}.#{file.extension}" if original_filename.present?

  end

 

  def default_url  #可以定义默认图片，如过用户没有上传图片，则可以使用默认的图片

    "/sfile/default4.jpg"

  end

#图片的处理，有不同版本大小，网站可以在不同的地方调用不同的图片大小  

 version :photo_big do

    process :resize_to_fit => [480,nil]  #fit是先规定图片的长或宽，再等比例缩放没规定的长或宽

  end

  version :photo_small do

    process :resize_to_fill => [180,100]  #fill硬性规定图片的长或宽

  end

  # Add a white list of extensions which are allowed to be uploaded.

  # For images you might use something like this:

#指定上传文件的格式

  def extension_white_list

    %w(jpg jpeg gif png)

   end

 protected

  def secure_token

    var = :"@#{mounted_as}_secure_token"

    model.instance_variable_get(var) or model.instance_variable_set(var, SecureRandom.uuid)

  end

  # Override the filename of the uploaded files:

  # Avoid using model.id or version_name here, see uploader/store.rb for details.

  # def filename

  #   "something.jpg" if original_filename

  # end

end








7.如何在表单中上传
<%= form_for(@user) do |f| %>
  <div class="field">
    <%= f.file_field :avatar %>
    <%= f.hidden_field :avatar_cache %>
  </div>
...
<%end%>


8.如何显示图片

 <%= image_tag(@user.avatar_url(:photo_big)) if @user.avatar %> 
或
<img src="<%= @user.avatar_url(:photo_big) -%>" >