Poorly scaled Jpeg image using c #

I'm trying to downsize a jpeg image from 3028x4051 to 854x1171. The result is an image close to 1M pixels and maintains the aspect ratio. The original image is here . However, the image deteriorates greatly. Below is a snippet of the image. The upper part is the image zoomed out in MS mask, the lower part is shortened programmatically in C #. I included the code I used to zoom out and save it. Does anyone know what might happen?

using (IRandomAccessStream sourceStream = await sourceFile.OpenAsync(FileAccessMode.Read))
{
    BitmapDecoder myDecoder = await GetDecoder(sourceStream);
    BitmapTransform myTransform = new BitmapTransform() { ScaledHeight = h, ScaledWidth = w };
    await myDecoder.GetPixelDataAsync(
            BitmapPixelFormat.Rgba8,
            BitmapAlphaMode.Premultiplied,
            myTransform,
            ExifOrientationMode.IgnoreExifOrientation,
            ColorManagementMode.DoNotColorManage);
    BitmapEncoder myEncoder = await BitmapEncoder.CreateAsync(BitmapEncoder.JpegEncoderId, destinationStream);
            myEncoder.SetPixelData(BitmapPixelFormat.Rgba8, BitmapAlphaMode.Premultiplied, w, h, 96, 96, pixelData.DetachPixelData());
    await myEncoder.FlushAsync();
}