Railsで、画像をアップロード、ダウンロードするREST API ref: http://qiita.com/ocadaruma/items/d12a80f7dbe07dd851a4

file0.txt

$ rails g model Image tag:string data:binary
$ rake db:migrate

file2.txt

$ rails g controller Images

file4.txt

$ rails s
$ curl --request POST -H 'Content-Type: application/json' -d '{"tag":"trumpet"}' http://localhost:3000/images
$ curl --request PUT -H 'Content-Type: application/octet-stream' --data-binary "@icon.png" http://localhost:3000/images/1/upload
$ curl http://localhost:3000/images/1/download > icon_downloaded.png

images_controller.rb

class ImagesController < ApplicationController
  def show
    image = Image.find(params[:id])
    render json: image, except: [:data]
  end

  def create
    image = Image.new
    image.tag = params[:tag]
    image.save!
    render json: image, except: [:data]
  end

  def download
    image = Image.find(params[:id])
    send_data image.data, type: "image/png", disposition: 'inline'
  end

  def upload
    image = Image.find(params[:id])
    image.data = request.raw_post
    image.save!
    render json: image, except: [:data]
  end
end

routes.rb

get 'images/:id' => 'images#show'
post 'images' => 'images#create'

get 'images/:id/download' => 'images#download'
put 'images/:id/upload' => 'images#upload'