A local Ruby script example with fileutils, open-uri, rmagick and mysql

##################################
# a code example for writing a ruby script to be running locally
# to do some regular local jobs such as:
# 1, download files or images from Internet
# 2, local file operations like mkdir, cp and remove
# 3, access or store data into local database like mysql
# 4, image resizing or cropping using image-magick
##################################

require 'open-uri'
require 'fileutils'
require 'RMagick'
require 'mysql'

# init local directories
FileUtils.mkdir_p "original/montreal"
FileUtils.mkdir_p "thumbnailed/montreal"

# init the database access
db = Mysql::new('127.0.0.1', 'root', '12345', 'test')

# init links to Internet
base_url = "http://farm1.static.flickr.com/"
image_urls = ['40/123180238_552597a079_b.jpg',
'146/390735501_54f0b2e826_b.jpg',
'50/131278273_4ce6400bfa_b.jpg']

# create a table to store image names
db.query("DROP TABLE IF EXISTS images")
db.query("CREATE TABLE images (name VARCHAR(64))")
image_urls.each do |image|
db.query("INSERT INTO images (name) VALUES ('#{image}')")
end

# download images from Internet
for i in 0..2
open("original/montreal/#{i}.jpg", 'wb').write(open("#{base_url}#{image_urls[i]}").read)
end

# resize and crop images
for i in 0..2
image = Magick::Image.read("original/montreal/#{i}.jpg").first
image.crop_resized!(150, 150, Magick::NorthGravity)
image.write("thumbnailed/montreal/#{i}.jpg")
end

References:

Ruby MySQL: http://www.tmtm.org/en/mysql/ruby/
RMagick: Making thumbnails with RMagick
FileUtils: http://www.ruby-doc.org/stdlib/libdoc/fileutils/rdoc/index.html
Ruby OpenURI: http://www.ruby-doc.org/core/classes/OpenURI.html

Basic flow to use rails file_column plugin

1. Create your table with a string field to store file name. For example:

create_table :products do |t|
t.string "name"
t.string "model"
t.string "image"
t.timestamps
end

2. Install file_column plugin:

script/plugin install http://opensvn.csie.org/rails_file_column/plugins/file_column/trunk

3. Install ImageMagick to your system and plugin RMagick

Visit http://rmagick.rubyforge.org/ for more detail

4. Put file_column description for model field into your model code. For example here, add to product.rb:

file_column :image, :magick => {
:versions => { "thumb" => "60x60", "medium" => "320x240"}
}

5. Generate controller and views for your model. I use rails 2.0 scaffold generator here:

script/generate scaffold product --skip-migration
add layout and authentication before_filter to product controller if needed
add _form.html.erb with form fields for new.html.erb and edit.html.erb to use
edit index.html.erb to show the list of products, such as <%= f.text_field :name %>

6. Show and upload image of product, edit in the _form.html.erb:

remove <%= f.text_field :image %>
add:
<% if !@product.id.nil? # in the case of edit %>
<%= image_tag url_for_file_column("product", "image", "medium") %>
<% end %>
<%= file_column_field "product", "image" %>

7. Add multipart to form tag in the edit and new files.

<% form_for(@product, :html => {:multipart => true}) do |f| %>

8. To show image in the list:

<% @product = product %>
<%= image_tag url_for_file_column("product", "image", "thumb") %>

Run Ruby, Gems, Rails, MySQL and RMagick on Cygwin

Before using cygwin, I did not expect that the commands of rails do not work in cygwin. To make ruby, gems and rails to work, there are some additional tasks to do as following:

• Add devel -> make + ruby + gcc + subversion modules from cygwin installation
• Download gems tgz install package from Ruby Gems download home
• tar xzvf rubygems-1.0.x.tgz
• cd rubygems-1.0.x
• unset RUBYOPT (before install gems, clear RUBYOPT=rubygems)
• ruby setup.rb
• gem install rails --include-dependencies
• Download mysql source tar.gz file from MySQL download page
• tar xzvf mysql-5.0.45.tar.gz
• cd mysql-5.0.45
• ./configure
• make install ( or to do it faster, just make install under sub directories libmysql and include.
• gem install mysql
• Change the database server from localhost to 127.0.0.1 in the database.yml of your rails app
• Install ImageMagick, libmagick-devel, XFree86-lib-compat, xorg-x11-devel, libbz2-devel module from cygwin installation file
• gem install RMagick
  
• ruby script/server. voila!
  

References:

Labnotes: Setting up Ruby + Gems on Cygwin
Softpedia: Install Rails on Windows with cygwin