adding hash ability to image loader (reducing the load on memory)

Wox.Infrastructure/Image/ImageHashGenerator.cs

@@ -0,0 +1,47 @@
+using System;
+using System.IO;
+using System.Security.Cryptography;
+using System.Windows.Media;
+using System.Windows.Media.Imaging;
+
+namespace Wox.Infrastructure.Image
+{
+    public interface IImageHashGenerator
+    {
+        string GetHashFromImage(ImageSource image);
+    }
+    public class ImageHashGenerator : IImageHashGenerator
+    {
+        public string GetHashFromImage(ImageSource imageSource)
+        {
+            if (!(imageSource is BitmapSource image))
+            {
+                return null;
+            }
+
+            try
+            {
+                using (var outStream = new MemoryStream())
+                {
+                    // PngBitmapEncoder enc2 = new PngBitmapEncoder();
+                    // enc2.Frames.Add(BitmapFrame.Create(tt));
+                    
+                    var enc = new JpegBitmapEncoder();
+                    enc.Frames.Add(BitmapFrame.Create(image));
+                    enc.Save(outStream);
+                    var byteArray = outStream.GetBuffer();
+                    using (var sha1 = new SHA1CryptoServiceProvider())
+                    {
+                        var hash = Convert.ToBase64String(sha1.ComputeHash(byteArray));
+                        return hash;
+                    }
+                }
+            }
+            catch
+            {
+                return null;
+            }
+
+        }
+    }
+}