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Newtonsoft.Json deserializes a base64 image

I am using Newtonsoft.Json to deserialize the output from my web service for an object. It worked fine until I added a property Bitmapto my class (named User) to store the avatar.

Webservice returns this property as a Base64 string, which is as expected. The problem is that when I try to convert JSON from WS to List<User>, a JsonSerializationExceptionis called in this block of code:

// T is IList<User>
response.Content.ReadAsStringAsync().Proceed(
    (readTask) =>
    {
        var json = ((Task<string>)readTask).Result;
        var result = JsonConvert.DeserializeObject<T>(json); //<-- it fails here

         // do stuff! 
     });

Exit exception:

Error converting value "System.Drawing.Bitmap" to type 'System.Drawing.Bitmap'. Path '[2].Avatar

and looking at an internal exception:

{"Could not cast or convert from System.String to System.Drawing.Bitmap."}

It is clear that it does not parse the Base64 string, but it is not clear why.

Any ideas / workarounds?

, Convert.FromBase64String . , , . , JSON. ?

2 : JSON webservice ( ). , , . - "System.Drawing.Bitmap" base64. , JsonSerializationException.

, , , - byte [].

+5
3

,

Convert.FromBase64String

Bitmap.FromStream(new MemoryStream(bytearray));

/

public class AClass
{
    public Bitmap image;
    public int i;
}

Bitmap bmp = (Bitmap)Bitmap.FromFile(@"......");
var json = JsonConvert.SerializeObject(new AClass() { image = bmp, i = 666 }, 
                                       new ImageConverter());

var aclass = JsonConvert.DeserializeObject<AClass>(json, new ImageConverter());

ImageConverter

public class ImageConverter : Newtonsoft.Json.JsonConverter
{
    public override bool CanConvert(Type objectType)
    {
        return objectType == typeof(Bitmap);
    }

    public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
    {
        var m = new MemoryStream(Convert.FromBase64String((string)reader.Value));
        return (Bitmap)Bitmap.FromStream(m);
    }

    public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
    {
        Bitmap bmp = (Bitmap)value;
        MemoryStream m = new MemoryStream();
        bmp.Save(m, System.Drawing.Imaging.ImageFormat.Jpeg);

        writer.WriteValue(Convert.ToBase64String(m.ToArray()));
    }
}
+9

,

[Serializable]
public class MyClass
{
    [JsonConverter(typeof(CustomBitmapConverter))]
    public Bitmap MyImage { get; set; }


    #region JsonConverterBitmap
    internal class CustomBitmapConverter : JsonConverter
    {
        public override bool CanConvert(Type objectType)
        {
            return true;
        }

        //convert from byte to bitmap (deserialize)

        public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
        {
            string image = (string)reader.Value;

            byte[] byteBuffer = Convert.FromBase64String(image);
            MemoryStream memoryStream = new MemoryStream(byteBuffer);
            memoryStream.Position = 0;

            return (Bitmap)Bitmap.FromStream(memoryStream);
        }

        //convert bitmap to byte (serialize)
        public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
        {
            Bitmap bitmap = (Bitmap)value;

            ImageConverter converter = new ImageConverter();
            writer.WriteValue((byte[])converter.ConvertTo(bitmap, typeof(byte[])));
        }

        public static System.Drawing.Imaging.ImageFormat GetImageFormat(Bitmap bitmap)
        {
            ImageFormat img = bitmap.RawFormat;

            if (img.Equals(System.Drawing.Imaging.ImageFormat.Jpeg))
                return System.Drawing.Imaging.ImageFormat.Jpeg;
            if (img.Equals(System.Drawing.Imaging.ImageFormat.Bmp))
                return System.Drawing.Imaging.ImageFormat.Bmp;
            if (img.Equals(System.Drawing.Imaging.ImageFormat.Png))
                return System.Drawing.Imaging.ImageFormat.Png;
            if (img.Equals(System.Drawing.Imaging.ImageFormat.Emf))
                return System.Drawing.Imaging.ImageFormat.Emf;
            if (img.Equals(System.Drawing.Imaging.ImageFormat.Exif))
                return System.Drawing.Imaging.ImageFormat.Exif;
            if (img.Equals(System.Drawing.Imaging.ImageFormat.Gif))
                return System.Drawing.Imaging.ImageFormat.Gif;
            if (img.Equals(System.Drawing.Imaging.ImageFormat.Icon))
                return System.Drawing.Imaging.ImageFormat.Icon;
            if (img.Equals(System.Drawing.Imaging.ImageFormat.MemoryBmp))
                return System.Drawing.Imaging.ImageFormat.MemoryBmp;
            if (img.Equals(System.Drawing.Imaging.ImageFormat.Tiff))
                return System.Drawing.Imaging.ImageFormat.Tiff;
            else
                return System.Drawing.Imaging.ImageFormat.Wmf;
        }

    }

    #endregion
+6

, Base64 System.Drawing.Bitmap . , , Avatar

, : JSON.Net

I think the best you can do is use Regexto remove the property from the json string:

var newJsonString = Regex.Replace(jsonString, 
                                  "(\\,)* \"Avatar\": \"[A-Za-z0-9]+\"", 
                                  String.Empty);

and then deserialize this one newJsonStringwithout the Avatar property.

Later you can parse the json source string to get Base64and buildBitmap

var avatarBase64 = Regex.Match(
                        Regex.Match(json, "(\\,)* \"Avatar\": \"[A-Za-z0-9]+\"")
                             .ToString(), 
                        "[A-Za-z0-9]+", RegexOptions.RightToLeft)
                        .ToString();

...

byte[] fromBase64 = Convert.FromBase64String(avatarBase64);
using (MemoryStream ms = new MemoryStream(fromBase64))
{
    Bitmap img = (Bitmap)Image.FromStream(ms);
    result.Avatar = img;
}

You can improve regular expressions or a method, but this is the main idea.

+1
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