Basic image resizing in Ruby on Rails

I tried following way. Its working fine. I hope it will help to some one.

1.add following gem in Gemfile:

gem "ImageResize", "~> 0.0.5"

2.run bundle

3.use this in controller function:

require 'rubygems'
require 'ImageResize'

#input_image_filename, output_image_filename, max_width, max_height
Image.resize('big.jpg', 'small.jpg', 40, 40)

You can resize with RMagick gem.

This is just a example that you can adapt:

require 'RMagick'

f = File.new( File.join(save_path, self.filename), "wb"  )
f.write form_file.read #remeber to set :html=>{:multipart => true} in form
f.close

image = Magick::Image.read(self.filename).first
image.change_geometry!("640x480") { |cols, rows, img|
    newimg = img.resize(cols, rows)
    newimg.write("newfilename.jpg")
}

More Info here: http://www.imagemagick.org/script/api.php#ruby

Simply use paperclip or attachment_fu