Windows Phone ImageHelper class

ImageHelper.cs

using System;
using System.IO;
using System.Windows.Media.Imaging;

namespace Helpers
{
    public class ImageHelper
    {
        public static MemoryStream ResizeImage(Stream inputStream, double maxWidth, double maxHeight)
        {
            using (inputStream)
            {
                var originalBitmapImage = new BitmapImage();

                originalBitmapImage.SetSource(inputStream);

                var scale = Math.Min(maxWidth / (double)originalBitmapImage.PixelWidth, maxHeight / (double)originalBitmapImage.PixelHeight);

                var writeableBitmap = new WriteableBitmap(originalBitmapImage);

                var outputStream = new MemoryStream();

                writeableBitmap.SaveJpeg(outputStream, (int)(originalBitmapImage.PixelWidth * scale), (int)(originalBitmapImage.PixelHeight * scale), 0, 90);

                return outputStream;
            }
        }
    }
}