windows store app 读写图片

  1 using System;
  2 using System.Threading.Tasks;
  3 using System.Runtime.InteropServices.WindowsRuntime;
  4 using Windows.Graphics.Imaging;
  5 using Windows.UI.Xaml.Media.Imaging;
  6 using Windows.Storage;
  7 using Windows.Storage.Pickers;
  8 using Windows.Storage.Streams;
  9 using System.IO;
 10 using Windows.Foundation;
 11 using System.Collections.Generic;
 12 
 13 namespace Common
 14 {
 15     public class ImageHelper
 16     {
 17         public const int THumbLength = 400;
 18         public  static Size MinSizeSupported = new Size(200, 200);
 19         public static Size MaxSizeSupported = new Size(4000, 3000);
 20 
 21         static Guid EncoderIDFromFileExtension(string strExtension)
 22         {
 23             Guid encoderId;
 24             switch (strExtension.ToLower())
 25             {
 26                 case ".jpg":
 27                 case ".jpeg":
 28                     encoderId = BitmapEncoder.JpegEncoderId;
 29                     break;
 30                 case ".bmp":
 31                     encoderId = BitmapEncoder.BmpEncoderId;
 32                     break;
 33                 case ".png":
 34                 default:
 35                     encoderId = BitmapEncoder.PngEncoderId;
 36                     break;
 37             }
 38             return encoderId;
 39         }
 40         static Guid DecoderIDFromFileExtension(string strExtension)
 41         {
 42             Guid encoderId;
 43             switch (strExtension.ToLower())
 44             {
 45                 case ".jpg":
 46                 case ".jpeg":
 47                     encoderId = BitmapDecoder.JpegDecoderId;
 48                     break;
 49                 case ".bmp":
 50                     encoderId = BitmapDecoder.BmpDecoderId;
 51                     break;
 52                 case ".png":
 53                 default:
 54                     encoderId = BitmapDecoder.PngDecoderId;
 55                     break;
 56             }
 57             return encoderId;
 58         }
 59 
 60         public async static Task<WriteableBitmap> ReadBitmap(IRandomAccessStream fileStream, string type)
 61         {
 62             WriteableBitmap bitmap = null;
 63             try
 64             {
 65                 Guid decoderId = DecoderIDFromFileExtension(type);
 66 
 67                 BitmapDecoder decoder = await BitmapDecoder.CreateAsync(decoderId, fileStream);
 68                 BitmapTransform tf = new BitmapTransform();
 69 
 70                 uint width = decoder.OrientedPixelWidth;
 71                 uint height = decoder.OrientedPixelHeight;
 72                 double dScale = 1;
 73 
 74                 if (decoder.OrientedPixelWidth > MaxSizeSupported.Width || decoder.OrientedPixelHeight > MaxSizeSupported.Height)
 75                 {
 76                     dScale = Math.Min(MaxSizeSupported.Width / decoder.OrientedPixelWidth, MaxSizeSupported.Height/decoder.OrientedPixelHeight );
 77                     width =(uint)( decoder.OrientedPixelWidth * dScale);
 78                     height = (uint)(decoder.OrientedPixelHeight * dScale);
 79 
 80                     tf.ScaledWidth = (uint)(decoder.PixelWidth* dScale); 
 81                     tf.ScaledHeight = (uint)(decoder.PixelHeight* dScale); 
 82                 }
 83 
 84                
 85                 bitmap = new WriteableBitmap((int)width, (int)height);
 86                 
 87                 
 88 
 89                 PixelDataProvider dataprovider = await decoder.GetPixelDataAsync(BitmapPixelFormat.Bgra8, BitmapAlphaMode.Straight, tf,
 90                     ExifOrientationMode.RespectExifOrientation, ColorManagementMode.DoNotColorManage);
 91                 byte[] pixels = dataprovider.DetachPixelData();
 92 
 93                 Stream pixelStream2 = bitmap.PixelBuffer.AsStream();
 94 
 95                 pixelStream2.Write(pixels, 0, pixels.Length);
 96                 //bitmap.SetSource(fileStream);
 97             }
 98             catch
 99             {
100             }
101 
102             return bitmap;
103         }
104 
105         public async static Task<WriteableBitmap> ReadBitmap(StorageFile file)
106         {
107             IRandomAccessStream stream = await file.OpenAsync(Windows.Storage.FileAccessMode.Read);
108             WriteableBitmap bitmap = await ReadBitmap(stream, file.FileType.ToLower());
109 
110             return bitmap;
111         }
112 
113 
114         public async static Task<bool> SaveBitmap(IRandomAccessStream stream, Guid encoderId, WriteableBitmap bitmap, BitmapTransform bitmapTransform)
115         {
116             bool bSuccess = true;
117             try
118             {
119                 Stream pixelStream = bitmap.PixelBuffer.AsStream();
120 
121                 BitmapEncoder encoder = await BitmapEncoder.CreateAsync(encoderId, stream);
122                 if (bitmapTransform != null)
123                 {
124                     encoder.BitmapTransform.ScaledWidth = bitmapTransform.ScaledWidth;
125                     encoder.BitmapTransform.ScaledHeight = bitmapTransform.ScaledHeight;
126                     encoder.BitmapTransform.InterpolationMode = BitmapInterpolationMode.Fant;
127                     encoder.BitmapTransform.Bounds = bitmapTransform.Bounds;
128                 }
129 
130                 byte[] pixels = new byte[pixelStream.Length];
131 
132                 pixelStream.Read(pixels, 0, pixels.Length);
133 
134                 encoder.SetPixelData(
135                     BitmapPixelFormat.Bgra8,
136                     BitmapAlphaMode.Straight,
137                     (uint)bitmap.PixelWidth,
138                     (uint)bitmap.PixelHeight,
139                     96, // Horizontal DPI
140                     96, // Vertical DPI
141                     pixels
142                 );
143                 await encoder.FlushAsync();
144                
145                 pixelStream.Dispose();
146             }
147             catch
148             {
149                 bSuccess = false;
150             }
151 
152             return bSuccess;
153         }
154 
155          async static Task<bool> SaveBitmap(StorageFile file, WriteableBitmap bitmap, BitmapTransform bitmapTransform)
156         {
157             bool bSuccess = true;
158             try
159             {
160                 // Application now has read/write access to the saved file
161                 Guid encoderId = EncoderIDFromFileExtension(file.FileType);
162 
163                 
164                 IRandomAccessStream fileStream = await file.OpenAsync(Windows.Storage.FileAccessMode.ReadWrite);
165 
166                 bSuccess = await SaveBitmap(fileStream, encoderId,bitmap,bitmapTransform);
167 
168                 fileStream.Dispose();
169               
170             }
171             catch
172             {
173                 bSuccess = false;
174             }
175 
176             return bSuccess;
177         }
178 
179         public async static Task<bool> SaveBitmap(StorageFile file, WriteableBitmap bitmap)
180         {
181             bool bSuccess = await SaveBitmap(file, bitmap, null);
182             return bSuccess;
183         }
184 
185         public async static Task<bool> SaveBitmapWithFilePicker(WriteableBitmap bitmap)
186         {
187             FileSavePicker save = new FileSavePicker();
188             save.SuggestedStartLocation = PickerLocationId.PicturesLibrary;
189             save.DefaultFileExtension = ".jpg";
190             save.SuggestedFileName = "new image";
191             save.FileTypeChoices.Add(".bmp", new List<string>() { ".bmp" });
192             save.FileTypeChoices.Add(".png", new List<string>() { ".png" });
193             save.FileTypeChoices.Add(".jpg", new List<string>() { ".jpg", ".jpeg" });
194 
195             StorageFile savedItem = await save.PickSaveFileAsync();
196             if (savedItem == null)
197             {
198                 return false;
199             }
200 
201             return await SaveBitmap(savedItem, bitmap);
202         }
203 
204         public async static Task<bool> SaveBitmapAsThumb(StorageFile file, WriteableBitmap bitmap, double width, double height)
205         {
206             BitmapTransform transform = new BitmapTransform();
207 
208             double ratio = Math.Min(width / bitmap.PixelWidth, height / bitmap.PixelHeight);
209 
210             transform.ScaledWidth = (uint)(bitmap.PixelWidth * ratio);
211             transform.ScaledHeight = (uint)(bitmap.PixelHeight * ratio);
212             transform.InterpolationMode = BitmapInterpolationMode.Fant;
213 
214             return await SaveBitmap(file, bitmap, transform);
215         }
216         public async static Task<bool> SaveBitmapAsThumb(StorageFile file, WriteableBitmap bitmap,  Windows.Foundation.Rect cropRect)
217         {
218             BitmapTransform transform = new BitmapTransform();
219 
220 
221             double ratio =THumbLength/ Math.Max(cropRect.Width, cropRect.Height );
222 
223             transform.ScaledWidth = (uint)(bitmap.PixelWidth * ratio);
224             transform.ScaledHeight = (uint)(bitmap.PixelHeight * ratio);
225             transform.Bounds = new BitmapBounds()
226             {
227                 X = (uint)(cropRect.X * ratio),
228                 Y = (uint)(cropRect.Y * ratio),
229                 Width = (uint)(cropRect.Width * ratio),
230                 Height = (uint)(cropRect.Height * ratio)
231             };
232             transform.InterpolationMode = BitmapInterpolationMode.Fant;
233 
234             return await SaveBitmap(file, bitmap, transform);
235         }
236     }
237 }