gistfile1.cs

	/// <summary>
	/// Gets a local Base64 string of the remote Image (14)
	/// e.g. /api/values?url=/sites/sitecollection/subweb/PictureOfTheThames.jpg
	/// </summary>
	/// <param name="path">Relative Site Path to the Image</param>
	/// <returns>Base64 string of the remote Image</returns>
	public async Task<string> Get([FromUri] string path)
	{
		string webAPIEndpoint = String.Format("{0}/_api/web/GetFileByServerRelativeUrl('{1}')/$Value", webAPIResourceID, path.Substring((path.ToLower().IndexOf("/sites"))));
				
		string type = path.Substring((path.LastIndexOf('.') + 1));
	
		try
		{
			/*
			GET THE AUTH HEADER HERE...
			   As detailed here...
			   http://blogs.msdn.com/b/kaevans/archive/2014/04/15/calling-o365-apis-from-your-web-api-on-behalf-of-a-user.aspx
			*/
			
			var client = new HttpClient();
			var request = new HttpRequestMessage(HttpMethod.Get, webAPIEndpoint);
			request.Headers.TryAddWithoutValidation("Authorization", authResult.CreateAuthorizationHeader());
	
			var response = await client.SendAsync(request);
			var imgBytes = await response.Content.ReadAsByteArrayAsync();
			
			string img = Convert.ToBase64String(imgBytes);
	
	        //data types and content types like 'JPEG' and not 'JPG'
			return String.Format("data:image/{0};base64,{1}", type, img).Replace("jpg","jpeg");
		}
		catch (Exception oops)
		{
			throw oops;
		}
	}