From: Ben Giddings <bg-rubytalk@...>
Date: 2007-10-16T07:12:31+09:00
Subject: Re: Does Image URL exist?

On Monday 15 October 2007, Tj Superfly wrote:
> Hello everyone, I've been trying to find a code that will let me see 
if
> an  image URL that I enter exists, but am having trouble.
> 
> Basically I just need something that will tell me yes or no if the 
image
> URL exists or not (meaning the Image is uploaded on the server).

If you don't care whether it's an image not, this is relatively easy, 
all you need to do is ask the server if the path exists (response code 
200) or if the path doesn't (response code 404).  You don't need to 
even download any of the content of the file.

If you care whether the path exists *and* it's an image, you'll need to 
check its mime type.  If you're pretty sure the server is doing the 
right thing you can do this with a a HTTP head and not transfer the 
contents.  If you really want to make sure it's an image you'll have to 
download it and verify the file.

I think checking with an HTTP head that the content-type is an image 
content type should be enough, so something like this should do:

require 'uri'
require 'net/http'

url = URI.parse("http://example.com/images/yer_img_here.foo")

Net::HTTP.start(url.host, url.port) do |http| 
  response = http.head(url.path)
  case response
  when Net::HTTPSuccess, Net::HTTPRedirection
    case response.content_type
    when "image/png", "image/gif", "image/jpeg"
      puts "ok"
    else
      puts "nope"
    end
  else 
    puts "nope"
  end
end

Ben