using System;

 using System.Threading.Tasks;

 using Windows.Storage.Streams;

 using Windows.Foundation;

 using Windows.Graphics.Imaging;

 namespace ScanQRCode

 {

     public static class ImageHelper

     {

         /// <summary>

         /// Asynchronously get the cropped stream.

         /// </summary>

         /// <param name="inputStream">The input stream</param>

         /// <param name="rect"></param>

         /// <returns></returns>

         public static async Task<IRandomAccessStream> GetCroppedStreamAsync(IRandomAccessStream inputStream, Rect rect)

         {

             if (inputStream == null)

                 return null;

             var startPointX = (uint)Math.Floor(rect.X);

             var startPointY = (uint)Math.Floor(rect.Y);

             var width = (uint)Math.Floor(rect.Width);

             var height = (uint)Math.Floor(rect.Height);

             return await GetCroppedStreamAsync(inputStream, startPointX, startPointY, width, height);

         }

         /// <summary>

         /// Asynchronously get the cropped stream.

         /// </summary>

         /// <param name="inputStream">The input stream</param>

         /// <param name="x"></param>

         /// <param name="y"></param>

         /// <param name="width"></param>

         /// <param name="height"></param>

         /// <returns></returns>

         public static async Task<IRandomAccessStream> GetCroppedStreamAsync(IRandomAccessStream inputStream, uint x, uint y, uint width, uint height)

         {

             if (inputStream == null)

                 return null;

             var pixelData = await GetCroppedPixelDataAsync(inputStream, x, y, width, height);

             if (pixelData == null)

                 return null;

             var outputStream = new InMemoryRandomAccessStream();

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

             encoder.SetPixelData(BitmapPixelFormat.Bgra8, BitmapAlphaMode.Ignore, width, height, , , pixelData);

             await encoder.FlushAsync();

             return outputStream;

         }

         /// <summary>

         /// Asynchronously get the cropped pixel data.

         /// </summary>

         /// <param name="inputStream">The input stream</param>

         /// <param name="rect"></param>

         /// <returns></returns>

         public static async Task<byte[]> GetCroppedPixelDataAsync(IRandomAccessStream inputStream, Rect rect)

         {

             if (inputStream == null)

                 return null;

             var startPointX = (uint)Math.Floor(rect.X);

             var startPointY = (uint)Math.Floor(rect.Y);

             var width = (uint)Math.Floor(rect.Width);

             var height = (uint)Math.Floor(rect.Height);

             return await GetCroppedPixelDataAsync(inputStream, startPointX, startPointY, width, height);

         }

         /// <summary>

         /// Asynchronously get the cropped pixel data.

         /// </summary>

         /// <param name="inputStream">The input stream</param>

         /// <param name="x"></param>

         /// <param name="y"></param>

         /// <param name="width"></param>

         /// <param name="height"></param>

         /// <returns></returns>

         public static async Task<byte[]> GetCroppedPixelDataAsync(IRandomAccessStream inputStream, uint x, uint y, uint width, uint height)

         {

             if (inputStream == null)

                 return null;

             var decoder = await BitmapDecoder.CreateAsync(inputStream);

             // Refine the start point

             if (x + width > decoder.PixelWidth)

                 x = decoder.PixelWidth - width;

             if (y + height > decoder.PixelHeight)

                 y = decoder.PixelHeight - height;

             var transform = new BitmapTransform()

             {

                 Bounds = new BitmapBounds

                 {

                     X = x,

                     Y = y,

                     Width = width,

                     Height = height

                 },

                 InterpolationMode = BitmapInterpolationMode.Fant,

                 ScaledWidth = decoder.PixelWidth,

                 ScaledHeight = decoder.PixelHeight

             };

             var pixelProvider = await decoder.GetPixelDataAsync(decoder.BitmapPixelFormat, decoder.BitmapAlphaMode, transform,

                                                      ExifOrientationMode.RespectExifOrientation, ColorManagementMode.ColorManageToSRgb);

             return pixelProvider.DetachPixelData();

         }

     }

 }