Here's a useful snippet in C#. This method gets all the images from variable type String. It can be HTML or XML text with tags <img src="path_to_image">

        public  static List<Uri> FetchImagesFromString(string htmlSource)
        {
            List<Uri> links = new List<Uri>();
            string regexImgSrc = @"<img[^>]*?src\s*=\s*[""']?([^'"" >]+?)[ '""][^>]*?>";
            MatchCollection matchesImgSrc = Regex.Matches(htmlSource, regexImgSrc, RegexOptions.IgnoreCase | RegexOptions.Singleline);
            foreach (Match m in matchesImgSrc)
            {
                string href = m.Groups[1].Value;
                links.Add(new Uri(href));
            }
            return links;
        }