Added image serializer

Added support for more image formats

src/Discord.Net.Core/Entities/Image.cs

@@ -7,13 +7,16 @@ namespace Discord
     public struct Image
     {
         public Stream Stream { get; }
+        public ImageFormat Format { get; }
+
         /// <summary>
         /// Create the image with a Stream.
         /// </summary>
         /// <param name="stream">This must be some type of stream with the contents of a file in it.</param>
-        public Image(Stream stream)
+        public Image(Stream stream, ImageFormat format = ImageFormat.Jpeg)
         {
             Stream = stream;
+            Format = format;
         }
 #if FILESYSTEM
         /// <summary>
@@ -23,9 +26,10 @@ namespace Discord
         /// This file path is NOT validated, and is passed directly into a <see cref="File.OpenRead(string)"/>
         /// </remarks>
         /// <param name="path">The path to the file.</param>
-        public Image(string path)
+        public Image(string path, ImageFormat format = ImageFormat.Jpeg)
         {
             Stream = File.OpenRead(path);
+            Format = format;
         }
 #endif
     }

src/Discord.Net.Rest/API/Image.cs

@@ -5,16 +5,19 @@ namespace Discord.API
     internal struct Image
     {
         public Stream Stream { get; }
+        public ImageFormat StreamFormat { get; }
         public string Hash { get; }
 
-        public Image(Stream stream)
+        public Image(Stream stream, ImageFormat format)
         {
             Stream = stream;
+            StreamFormat = format;
             Hash = null;
         }
         public Image(string hash)
         {
             Stream = null;
+            StreamFormat = ImageFormat.Jpeg;
             Hash = hash;
         }
     }

src/Discord.Net.Rest/Extensions/EntityExtensions.cs

@@ -114,7 +114,7 @@ namespace Discord.Rest
 
         public static API.Image ToModel(this Image entity)
         {
-            return new API.Image(entity.Stream);
+            return new API.Image(entity.Stream, entity.Format);
         }
 
         public static Overwrite ToEntity(this API.Overwrite model)

src/Discord.Net.Rest/Serialization/JsonConverters/ImagePropertyConverter.cs

@@ -1,12 +1,52 @@
-using System.Text.Json;
+using System;
+using System.Text.Json;
 
 namespace Discord.Serialization.Json.Converters
 {
     internal class ImagePropertyConverter : IJsonPropertyConverter<API.Image>
     {
         public API.Image Read(PropertyMap map, ref JsonReader reader, bool isTopLevel)
-            => throw new System.NotImplementedException();
+        {
+            if (isTopLevel)
+                reader.Read();
+            if (reader.ValueType != JsonValueType.String)
+                throw new SerializationException("Bad input, expected String");
+            return new API.Image(reader.ParseString());
+        }
         public void Write(PropertyMap map, ref JsonWriter writer, API.Image value, bool isTopLevel)
-            => throw new System.NotImplementedException();
+        {
+            string str;
+            if (value.Stream != null)
+            {
+                byte[] bytes = new byte[value.Stream.Length - value.Stream.Position];
+                value.Stream.Read(bytes, 0, bytes.Length);
+
+                string base64 = Convert.ToBase64String(bytes);
+                switch (value.StreamFormat)
+                {
+                    case ImageFormat.Jpeg:
+                        str = $"data:image/jpeg;base64,{base64}";
+                        break;
+                    case ImageFormat.Png:
+                        str = $"data:image/png;base64,{base64}";
+                        break;
+                    case ImageFormat.Gif:
+                        str = $"data:image/gif;base64,{base64}";
+                        break;
+                    case ImageFormat.WebP:
+                        str = $"data:image/webp;base64,{base64}";
+                        break;
+                    default:
+                        throw new SerializationException($"Unable to serialize an {nameof(Image)} with a format of {value.StreamFormat}");
+                }
+            }
+            else
+                str = value.Hash;
+
+            if (isTopLevel)
+                writer.WriteAttribute(map.Key, str);
+            else
+                writer.WriteValue(str);
+        }
     }
 }