从Windows Phone 8.1中的MediaCapture调整照片大小

Question

我想拍照，将其调整为1000x1000并将其保存到图片库。问题是图片左右两侧都有一个黑色边框，不透明。就像相机在我的预览区域外拍摄了一些像素。我也试图让CaptureElement像一个正方形，但MediaCapture流无法按预期填充该区域......

<Grid Style="{StaticResource LayoutGridStyle}">        
    <CaptureElement Name="CameraPreview" VerticalAlignment="Top" HorizontalAlignment="Left" />        
    <Button Content="Take photo" Click="TakePhoto_Click" HorizontalAlignment="Center" Margin="0,0,0,100" VerticalAlignment="Bottom" FontSize="30"/>                      
</Grid>

背后的相机页面代码

private async Task InitPreviewCaptureAsync()
    {
        CameraPreview.Width = Window.Current.Bounds.Width;
        CameraPreview.Height = Window.Current.Bounds.Height;
        CameraPreview.Source = MediaCapture;
        CameraPreview.Stretch = Windows.UI.Xaml.Media.Stretch.UniformToFill;            

        MediaCapture.SetPreviewRotation(VideoRotation.Clockwise90Degrees);
        await MediaCapture.StartPreviewAsync();

        Root.IsPreviewing = true;
        Root.PreviewElement = CameraPreview;
    }

private async Task<string> TakePhotoAsync()
    {
        string filename = string.Format("myphotoapp_{0}.jpg", DateTime.Now.ToString("yyMMddHHmms"));
        var imageFile = await KnownFolders.CameraRoll.CreateFileAsync(filename, CreationCollisionOption.GenerateUniqueName);
        await MediaCapture.CapturePhotoToStorageFileAsync(Windows.Media.MediaProperties.ImageEncodingProperties.CreateJpeg(), imageFile);            
        await Root.CleanupCaptureResourcesAsync();
        filename = imageFile.Name;
        imageFile = null;
        return filename;
    }

最后是从我的上传页面调整大小的代码

private async Task LoadImageAsync()
    {
        var imageFile = await KnownFolders.CameraRoll.GetFileAsync(StorageFileName);

        using (var sourceStream = await imageFile.OpenAsync(FileAccessMode.ReadWrite))
        {
            BitmapDecoder decoder = await BitmapDecoder.CreateAsync(sourceStream);

            ImageStream = new InMemoryRandomAccessStream();
            BitmapEncoder encoder = await BitmapEncoder.CreateForTranscodingAsync(ImageStream, decoder);
            encoder.BitmapTransform.ScaledWidth = 1000 * decoder.PixelWidth / decoder.PixelHeight;
            encoder.BitmapTransform.ScaledHeight = 1000;
            encoder.BitmapTransform.Bounds = new BitmapBounds { Height = 1000, Width = 1000, X = 0, Y = 0 };
            encoder.BitmapTransform.Rotation = BitmapRotation.Clockwise90Degrees;                
            await encoder.FlushAsync();

            BitmapImage bitmapImage = new BitmapImage();
            await bitmapImage.SetSourceAsync(ImageStream);
            UploadedImage.Source = bitmapImage;

            if (!ImageHasBeenResized)
            {
                using (var outputStream = sourceStream.GetOutputStreamAt(0))
                {
                    using (var inputStream = ImageStream.GetInputStreamAt(0))
                    {
                        IBuffer storageFileBuffer = new byte[ImageStream.Size].AsBuffer();
                        await inputStream.ReadAsync(storageFileBuffer, storageFileBuffer.Length, InputStreamOptions.None);
                        await outputStream.WriteAsync(storageFileBuffer);
                    }
                }
            }
        }
    }