gem 'carrierwave'

gem 'mini_magick'

rails generate uploader UserPic 

# 修改文件存储位置

  def store_dir

    # "uploads/#{model.class.to_s.underscore}/#{mounted_as}/#{model.id}"

    "user_head_pic"

  end

# 设置默认头像

  def default_url(*args)

    "/assets/user_head.png"

  end

# 修改文件名

  def filename

    if original_filename

      @name ||= Digest::MD5.hexdigest(current_path)

      "#{@name}#{file.basename}.#{file.extension}"

    end

  end

class AddHeadPicToUsers < ActiveRecord::Migration[5.1]

  def change

    add_column :users,:head_pic,:string,:comment=>'头像'

  end

end

class User < ActiveRecord::Base

      mount_uploader :head_pic, UserPicUploader

end

 def update_user_pic

    image_info = params[:avatar]||""

    if image_info.include? "data:image/png"

      png = Base64.decode64(image_info['data:image/png;base64,'.length .. -1])# 将 Base64 编码的参数用 Base64 解码，得到数据的二进制表示，也就是图片本身的二进制数据

      unless Dir.exists?("#{Rails.root}/public/user_head_pic")

        FileUtils.mkdir_p("#{Rails.root}/public/user_head_pic")

      end

      file_name = "img_#{@current_user.user_no}.png"# 根据当前用户工号声明一个文件名

      file_path = "#{Rails.root}/public/user_head_pic/#{file_name}" # 确定文件保存路径

      File.open(file_path,'wb') do |item|# 根据文件路径创建新文件

        item.write(png)# 将前面的二进制数据写到文件里

      end

      @current_user.head_pic = File.open(Rails.root+"public/user_head_pic/#{file_name}")

      @current_user.save

      flash[:notice] = "保存成功！"

    else

      flash[:notice] = "保存失败！"

    end

    redirect_to :action=>:update_head

  end

    <img src="<%= @user.head_pic.url%>" />