Resize image in bytes[] to a different sized image also in bytes[] - Windows 8

Question

I have this piece of code that retrieves a image from a webservice and saves it to a StorageFile

StorageFolder folder = await ApplicationData.Current.LocalFolder.CreateFolderAsync(Constants.DataDirectory, CreationCollisionOption.OpenIfExists);
StorageFile imgFile;

using (var httpClient = new HttpClient { BaseAddress = Constants.baseAddress })
{
    string token = App.Current.Resources["token"] as string;
    httpClient.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Bearer", token);

    using (var response2 = await httpClient.GetAsync("user/image?userId=" + id))
    {
        Stream imageStream = await response2.Content.ReadAsStreamAsync();
        if (imageStream.Length != 0)
        {
            byte[] bytes = new byte[imageStream.Length];
            imageStream.Read(bytes, 0, (int)imageStream.Length);
            imgFile = await folder.CreateFileAsync(fname, CreationCollisionOption.ReplaceExisting);
            await FileIO.WriteBytesAsync(imgFile, bytes);  //i want the image bytes to be of a smaller version of the image at this point
        }
        return await response2.Content.ReadAsStringAsync();
    }
}

I would like to know if there is a way to convert the image bytes[] to a thumbnail version (50x50 for example) before writing them into the StorageFile.

Answer 1

Here is the code to resize the image stream:

                var decoder = await BitmapDecoder.CreateAsync(stream);

                var pixels = await decoder.GetPixelDataAsync();

                var file = await folder.CreateFileAsync($"{_oriFile.DisplayName}_{size}.png",CreationCollisionOption.GenerateUniqueName);
                using (var fileStream = await file.OpenAsync(FileAccessMode.ReadWrite))
                {

                    var encoder = await BitmapEncoder.CreateAsync(BitmapEncoder.PngEncoderId, fileStream);

                    encoder.BitmapTransform.ScaledWidth = size;
                    encoder.BitmapTransform.ScaledHeight = size;

                    encoder.SetPixelData(
                        decoder.BitmapPixelFormat,
                        decoder.BitmapAlphaMode,
                        decoder.PixelWidth, decoder.PixelHeight,
                        decoder.DpiX, decoder.DpiY,
                        pixels.DetachPixelData());

                    encoder.BitmapTransform.InterpolationMode = BitmapInterpolationMode.Fant;

                    await encoder.FlushAsync();
                }

When you get the image stream, you should do the resize thing before saving it as StorageFile. Of course you can do this later after saving it to StorageFile.