writeablebitmap保存中出现的问题

Question

private async void SaveImage(WriteableBitmap src)
        {
            StorageFolder installedLocation = KnownFolders.PicturesLibrary;
            string name = DateTime.Now.ToString();
            foreach (char c in name)
            {
                if (c >= 48 && c <= 57) Name += c;
            }
            var _Folder = KnownFolders.PicturesLibrary;
            var _Folder1 = await _Folder.CreateFolderAsync(Name, Windows.Storage.CreationCollisionOption.ReplaceExisting);
            var File = await _Folder1.CreateFileAsync(Name, Windows.Storage.CreationCollisionOption.ReplaceExisting);    
            try
            {

                Guid encoderId= Windows.Graphics.Imaging.BitmapEncoder.JpegEncoderId;
                using (IRandomAccessStream fileStream = await File.OpenAsync(Windows.Storage.FileAccessMode.ReadWrite))
                {
                    Windows.Graphics.Imaging.BitmapEncoder encoder = await Windows.Graphics.Imaging.BitmapEncoder.CreateAsync(encoderId, fileStream);

                    Stream pixelStream = src.PixelBuffer.AsStream();

                    byte[] pixels = new byte[pixelStream.Length];

                    pixelStream.Read(pixels, 0, pixels.Length);

                    for (int i = 0; i < pixels.Length; i += 4)
                    {

                        byte temp = pixels[i];

                        pixels[i] = pixels[i + 2];

                        pixels[i + 2] = temp;

                    }
                    //pixal format shouldconvert to rgba8

                    encoder.SetPixelData(Windows.Graphics.Imaging.BitmapPixelFormat.Rgba8, Windows.Graphics.Imaging.BitmapAlphaMode.Straight,
                        (uint)src.PixelWidth, (uint)src.PixelHeight, 96, 96, pixels);

                    await encoder.FlushAsync();
                }

            }

            catch (Exception e)
            {

                throw e;

            }

     这段代码在保存时产生一个没有后缀名没有内容的文件。为什么？其实我只是想实现保存writeablebitmap但是不使用FileSavePicker save = new FileSavePicker();就是不需要用户选择直接保存的功能。

Answer 1

你的 应用清单中声明功能  有設定嗎 ?

Windows 应用商店应用中的文件访问和权限

至於檔名, 你可以用時間到毫秒來當檔名.

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Answer 2

设定了的。

Answer 3

 string str = ".jpg";

 StorageFolder Folder1 = await installedLocation.CreateFolderAsync(Name, Windows.Storage.CreationCollisionOption.ReplaceExisting);

  Name += str;

 StorageFile imageFile = await Folder1.CreateFileAsync(Name, CreationCollisionOption.GenerateUniqueName);        这样就可以了。Name中需要包含类型

Answer 4

可以了。谢谢。