Load bitmapImage from base64String

问题:

How can I load a bitmapImage from base64String in windows 8?

I tried this but I am not successful. It used to work on windows phone. What is different?

Looks like I have to use the function setsourceasync. When I use that, then I am required to pass the parameter as IRandomMemory which I am unable to do. How to do this?

    public static BitmapImage Base64ToImage(string base64String)
    {
        var bitmapImage = new BitmapImage();
        try
        {
            if (!String.IsNullOrEmpty(base64String))
            {
                var imageBytes = Convert.FromBase64String(base64String);
                using (var ms = new MemoryStream(imageBytes, 0, imageBytes.Length))
                {
                    bitmapImage.SetSourcec(ms);
                    return bitmapImage;
                }
            }
        }
        catch (Exception e)
        {

        }

        return null;
    }

回答1:

To create an IRandomAccessStream object for the SetSource method, you need to use a DataWriter. Take a look to this code:

    public async Task<BitmapImage> GetImage(string value)
    {
        if (value == null)
            return null;

        var buffer = System.Convert.FromBase64String(value);
        using (InMemoryRandomAccessStream ms = new InMemoryRandomAccessStream())
        {
            using (DataWriter writer = new DataWriter(ms.GetOutputStreamAt(0)))
            {
                writer.WriteBytes(buffer);
                await writer.StoreAsync();
            }

            var image = new BitmapImage();
            image.SetSource(ms);
            return image;
        }
    }

回答2:

Here conversion methods for both System.Drawing.Bitmap and System.Windows.Media.BitmapSource.

Enjoy

Remark: Not tested on Win8 but there is not reason why it should not work.

    string ToBase64(Bitmap bitmap)
    {
        if (bitmap == null)
            throw new ArgumentNullException("bitmap");

        using (var stream = new MemoryStream())
        {
            bitmap.Save(stream, ImageFormat.Png);

            return Convert.ToBase64String(stream.ToArray());
        }
    }

    string ToBase64(BitmapSource bitmapSource)
    {
        using (var stream = new MemoryStream())
        {
            var encoder = new PngBitmapEncoder();
            encoder.Frames.Add(BitmapFrame.Create(bitmapSource));
            encoder.Save(stream);
            return Convert.ToBase64String(stream.ToArray());
        }
    }

    Bitmap FromBase64(string value)
    {
        if (value == null)
            throw new ArgumentNullException("value");

        using (var stream = new MemoryStream(Convert.FromBase64String(value)))
        {
            return (Bitmap)Image.FromStream(stream);
        }
    }

    BitmapSource BitmapSourceFromBase64(string value)
    {
        if (value == null)
            throw new ArgumentNullException("value");

        using (var stream = new MemoryStream(Convert.FromBase64String(value)))
        {
            var decoder = new PngBitmapDecoder(stream, BitmapCreateOptions.PreservePixelFormat, BitmapCacheOption.OnLoad);
            BitmapSource result = decoder.Frames[0];
            result.Freeze();
            return result;
        }
    }