Ajax uploads? Image manipulation & drag-and-drop sorting.

December 11th, 2006

Wouldn’t it be nice to allow uploads in a cool Ajaxy way? Well, because of security restrictions it’s just not possible. There are however ways to create the same effect.

Here’s a quick demo of an ajax-ish image upload as well as some image manipulation functionality, and drag and drop sorting. I’m not sure this will work on all browsers but it’s been tested successfully with most. This was created about 4 months ago and I never had time to polish any of it up so take what you can from it.

http://www.naffis.com/demos/image_demo

First our layout (layouts/image_demo.rhtml):

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/strict.dtd">
<html>
    <head>
        <title>Image Demo</title>
        <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">        
        <%= javascript_include_tag :defaults %>
        <%= stylesheet_link_tag 'image_demo' %>
    </head>
    <body>
        <div id="titlebar">Image Demo</div>

        <%= render :partial => "upload_form" %>    

        <div id="centercontent">
            <%= yield %>
        </div>
        <div id="next">
            <%= link_to "Create Animated Gif", :action => "animate" %>
        </div>
        <div id="bottom">
            &copy; naffis.com 2006 
        </div>

    </body>
</html>

We’re going to extend the form_remote_tag to handle file uploads.

Drop this in your lib directory (lib/remote_uploads.rb):

module ActionView
  module Helpers
    module PrototypeHelper
      alias_method :form_remote_tag_old, :form_remote_tag
      def form_remote_tag(options = {})
        if options[:html] && options[:html][:multipart]      
          uid = "a#{Time.now.to_f.hash}"                                
          <<-STR    
          <iframe name="#{uid}" id="#{uid}" src="about:blank" style="position:absolute;left:-100px;width:0px;height:0px;border:0px"></iframe>
          <form method="post" action="#{url_for options[:url].update({:iframe_remote => true})}" enctype="multipart/form-data" target="#{uid}" #{%(onsubmit="#{options[:loading]}") if options[:loading]}>
          STR
        else
          form_remote_tag_old(options)
        end
      end                             
    end
  end
end

Add the require in your environment.rb:

require 'remote_uploads.rb'

This will create a custom form for file uploads (multipart => true) that submits to a hidden iframe. If it’s not a file upload then it will revert to the standard form_remote_tag of PrototypeHelper.

Some boring half baked styles for our demo:

body {
  background-color:        #FFFFFF;
  background-image:        url(/maps/images/gradient.jpg);
  background-repeat:    no-repeat;
  color:                            #666666;
  font-family:                arial, sans;
  font-size:                    100%;
  line-height:                1.7em;
  margin:                            1em 2em;
}

#titlebar {
  font-size:                     1.2em;
  border-bottom:                    2px solid #333333;
  margin-bottom:                    1em;
  padding-bottom:                1em;
}

h2 {
  font-size:                     1.2em;
}

ul.navigation {
  background-color:        #333333;
  padding:                        0em 0.5em;
  list-style-type:        none;
}

ul.navigation li {
  border-right:                1px solid #666666;
  display:                        inline;
}

.navigation a {
  color:                            #FFFFFF;
  padding:                        0.5em;
}

.description {
  font-size:                    1.2em;
}

.upload {
  font-size:                    1.2em;
}

strong {
  background-color:        #FFFF99;
}

#centercontent {
  width: 100%;
  text-align: center;
  margin-bottom:                1em;
  padding-bottom:                1em;                
  margin-top:                    1em;
  padding-top:                1em;
}

#bottom {                
    width: 100%;
    float: left;
    text-align: center;
    border-top:                    2px solid #333333;
    margin-top:                    1em;
    padding-top:                1em;
}

div.float {
  width: 120px;
  padding: 10px;
  float: left;
}

div.spacer {
  clear: both;
}

div.float img {
  margin-left: 5px;
  }

div.float p {
  font-size: 9px;
  text-align: center;
  }            

#image-list ul {    
  list-style: none;
}

#image-list ul li {
  list-style: none;
  display: inline; 
    float: left;  
    width: 120px; 
    height: 120px; 
    padding: 10px;
  border: 1px solid #000;      
}

We’re using Sean Treadway’s responds_to_parent plugin (http://sean.treadway.info/svn/plugins/responds_to_parent/) to execute our RJS generated javascript in the parent window instead of the iframe which the file upload is submitted to. There are other ways of doing this that use less code but the plugin is simple so why not use it?

Everything from this point on is pretty self explanitory. I can expand on it later but here’s the rest of the code.

Our index: 

<div id="image-list">
    <ul id="sortable_list">
        <% for @asset in @assets %>
            <%= render :partial => "image_container", :locals => { :asset => @asset } %>
        <% end %>
    </ul>
</div>
<%= sortable_element('sortable_list', :constraint => false, :url => {:action => :update_positions}) %>

Some partials used above:

_image_container.rhtml 

<li id="item_<%= @asset.id %>" class="float">
    <%= render :partial => "image_thumb", :locals => { :asset => @asset } %>
</li>

_image_thumb.rhtml 

<%= image_tag @asset.thumbnail, :border => 2 %>
    <br>
    <%= link_to_remote(image_tag("arrow_rotate_anticlockwise.png", :border => 0), :url => {:action => "rotate", :id => @asset.id, :direction => "left"} ) %>
    &nbsp;
    <%= link_to_remote(image_tag("cross.png", :border => 0), :url => {:action => "remove", :id => @asset.id} ) %>
    &nbsp;
    <%= link_to_remote(image_tag("arrow_rotate_clockwise.png", :border => 0), :url => {:action => "rotate", :id => @asset.id, :direction => "right"} ) %>

_upload_form.rhtml 

<%= form_remote_tag(:url => { 
        :controller => "image_demo", 
        :action => "create" },             
        :html => {:multipart => true}) %>
    <b>Picture:</b>&nbsp;
    <%= file_field_tag "asset" %>&nbsp;
    <%= submit_tag "Upload" %>&nbsp;
<%= end_form_tag %>

Our RJS to handle the create, remove, and rotate.

create.rjs 

if @asset.new_record?
  page.alert "There was a problem uploading your file:\n" +
  @asset.errors.full_messages.join("\n")
else
  page.insert_html :top, 'sortable_list', :partial => 'image_container', :locals => { :asset => @asset } 
  page.visual_effect :highlight, "item_#{@asset.id}"
  page.sortable "sortable_list", :constraint => false, :url => { :action => :update_positions }
end

remove.rjs 

page.remove "item_#{@asset_id}"
page.sortable "sortable_list", :constraint => false, :url => { :action => :update_positions }

rotate.rjs 

page.replace_html "item_#{@asset.id}", :partial => 'image_thumb', :locals => { :asset => @asset } 
page.visual_effect :highlight, "item_#{@asset.id}"
page.sortable "sortable_list", :constraint => false, :url => { :action => :update_positions }

Our controller: 

class ImageDemoController < ApplicationController 
  layout 'image_demo'

  def index
    session[:uid] = Time.now.to_i unless session[:uid]      
    @assets = Asset.find(:all, 
                         :conditions => ["user_id = ?", session[:uid].to_i],
    :order => "position")    
  end

  def create
    @asset = Asset.new()
    @asset.uploaded_file = params['asset']
    @asset.position = 0
    @asset.user_id = session[:uid].to_i
    @asset.save    
    responds_to_parent do
      render :action => 'create.rjs'
    end
    return
  end    

  def list
    @assets = Asset.find(:all, 
                         :conditions => ["user_id = ?", session[:uid].to_i],
    :order => "position")
  end  

  def update_positions
    params[:sortable_list].each_with_index do |id, position|
      Asset.update(id, :position => position)
    end
    render :nothing => true
  end

  def rotate
    @asset = Asset.find(params[:id])
    degrees = params[:direction] == "left" ? -90 : 90
    @asset.rotate(degrees)
  end

  def remove
    @asset_id = params[:id]
    Asset.delete(@asset_id)
  end

end

Our asset model: 

require 'RMagick'

class Asset < ActiveRecord::Base 

  def uploaded_file=(incoming_file)
    content_type = incoming_file.content_type.chomp
    if content_type.rindex(/image\/[(jpe?g)||(gif)]/)
      self.name = base_part_of(incoming_file.original_filename)

      base_dir = "/some/path/you/like"           

      # save original file
      self.original = "image_demo_assets/o_#{Time.now.utc.to_i}#{rand(1000000)}."+self.name
      File.open(base_dir+self.original,File::CREAT|File::TRUNC|File::WRONLY,0666){ |f|
        f.write(incoming_file.read)
      }      

      self.resized = "image_demo_assets/r_#{Time.now.utc.to_i}#{rand(1000000)}."+self.name
      resized = Magick::Image.read(base_dir+self.original).first
      resized.change_geometry!('500x500') { |cols, rows, img|
        img.resize!(cols, rows)
      }
      resized.write(base_dir+self.resized) 

      self.thumbnail = "image_demo_assets/t_#{Time.now.utc.to_i}#{rand(1000000)}."+self.name        
      thumb = Magick::Image.read(base_dir+self.original).first
      thumb.change_geometry!('100x100') { |cols, rows, img|
        img.resize!(cols, rows)
      }
      thumb.write(base_dir+self.thumbnail)     

      self.save    
    end
  end

  def rotate(degrees) 
    base_dir = "/some/path/you/like"       
    #main photo
    image = Magick::ImageList.new(base_dir+self.original)
    image = image.rotate(degrees)
    image.write(base_dir+self.original)

    # resized
    resized = Magick::ImageList.new(base_dir+self.resized)
    resized = resized.rotate(degrees)
    resized.write(base_dir+self.resized)    

    # thumb
    thumb = Magick::ImageList.new(base_dir+self.thumbnail)
    thumb = thumb.rotate(degrees)
    thumb.write(base_dir+self.thumbnail)    
  end

  private

  def base_part_of(file_name)
    name = File.basename(file_name)
    name.gsub(/[^W._-]/, '')
    sanitize_filename(name)
  end

  # Fixes a 'feature' of IE where it passes the entire path instead of just the filename
  def sanitize_filename(value)
    #get only the filename (not the whole path)
    just_filename = value.gsub(/^.*(\\|\/)/, '')
    just_filename.gsub(/[^\w\.\-]/,'_') 
  end

end

Some suggestions:
  • Use form_for and get rid of some ugliness in the controller by using Asset.new(params[:asset]) instead of setting each value individually.
  • Use simply_helpful for generiting your DOM id’s.
  • Use acts_as_attachment for handing the storing of files.
  • Better validations (aaa will handle that too).
  • Rewrite the whole thing.

Again, this is a VERY quick-and-dirty demo written in about 20 minutes with so much room for improvement. If I had the time I would, but alas I hope it helps.

Posted by dnaffis Filed in
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