wp8.1之拍照（获取焦点，使用后置摄像头）

wp8.1 没有像wp8一样直接用启动器开启摄像头，他要开启摄像头要借助CaptureElement呈现来自捕获设备（如照相机或网络摄像机）的流。今天讲讲如何打开摄像头，获取焦点，以及拍照。废话不多说，下面直接上代码。当然前提是一定要记住在appxmanifest文件Capabilities选项选择Webcam,不然会报错

首先 XAML代码：

 <Grid Name="LayoutRoot">
            <CaptureElement  x:Name="capturePreview" Stretch="UniformToFill"/>
            <Image Name="ProfilePic"></Image>
 </Grid>

  <StackPanel Grid.Row="1" VerticalAlignment="Bottom">
            <Slider x:Name="FocusValueSlider" Maximum="1000" Minimum="0" Grid.Row="0" Margin="12,0,15,0" Header="焦点调节:" ValueChanged="FocusValueSlider_ValueChanged" Value="500" SmallChang  e="1" LargeChange="25"></Slider>
            <StackPanel Orientation="Horizontal">
                <Button Content="启动摄像头" Click="PhotographButton_Click" ></Button>
                <Button Margin="50,0,0,0" Content="拍照" Click="CapturePhoto_Click"></Button>
            </StackPanel>
 </StackPanel>

然后是启动摄像头 事件：

    MediaCapture captureManager = null;

    async private void PhotographButton_Click(object sender, RoutedEventArgs e)
        {
            if (captureManager == null)
            {
                capturePreview.Visibility = Visibility.Visible;
                ProfilePic.Visibility = Visibility.Collapsed;
                captureManager = new MediaCapture();

                //选择后置摄像头
                var cameraID = await GetCameraID(Windows.Devices.Enumeration.Panel.Back);
                await captureManager.InitializeAsync(new MediaCaptureInitializationSettings
                {
                    StreamingCaptureMode = StreamingCaptureMode.Video,
                    PhotoCaptureSource = PhotoCaptureSource.Photo,
                    AudioDeviceId = string.Empty,
                    VideoDeviceId = cameraID.Id
                });
                 //摄像头旋转90度
                captureManager.SetPreviewRotation(VideoRotation.Clockwise90Degrees);
                capturePreview.Source = captureManager;
                await captureManager.StartPreviewAsync();
            }
        }

获取后摄像头方法：

     private static async Task<DeviceInformation> GetCameraID(Windows.Devices.Enumeration.Panel desired)
       {
           DeviceInformation deviceID = (await DeviceInformation.FindAllAsync(DeviceClass.VideoCapture))
               .FirstOrDefault(x => x.EnclosureLocation != null && x.EnclosureLocation.Panel == desired);

           if (deviceID != null) return deviceID;
           else throw new Exception(string.Format("Camera of type {0} doesn't exist.", desired));
       }

接下来是拍照方法：

 async private void CapturePhoto_Click(object sender, RoutedEventArgs e)
       {

           if (captureManager != null)
           {
               capturePreview.Visibility = Visibility.Collapsed;
               ProfilePic.Visibility = Visibility.Visible;
               //declare string for filename
               string captureFileName = string.Empty;

               //图片格式
               ImageEncodingProperties format = ImageEncodingProperties.CreateJpeg();

               //创建本地存储文件夹
               StorageFile file = await ApplicationData.Current.LocalFolder.CreateFileAsync(
                   "Photo.jpg",
                   CreationCollisionOption.ReplaceExisting);

               await captureManager.CapturePhotoToStorageFileAsync(format, file);

               BitmapImage bmpImage = new BitmapImage(new Uri(file.Path));

               ProfilePic.Source = bmpImage;
               
               //释放摄像头资源
               captureManager.Dispose();
               captureManager = null;
           }

       }

上面已经就完成了 拍照的一般流程，现在讲讲获取焦点，获取焦点的方法：

       private void FocusValueSlider_ValueChanged(object sender, RangeBaseValueChangedEventArgs e)
       {
           try
           {

               uint focus = Convert.ToUInt32(e.NewValue);
               SetFocus(focus);
           }
           catch
           {

           }
       }
     //设置摄像头焦点方法
     private async void SetFocus(uint? focusValue = null)
       {

           try
           {

               if (!focusValue.HasValue)
               {
                   focusValue = 500;
               }

               if (captureManager.VideoDeviceController.FocusControl.Supported)
               {

                   captureManager.VideoDeviceController.FlashControl.AssistantLightEnabled = false;

                   captureManager.VideoDeviceController.FocusControl.Configure(new FocusSettings() { Mode = FocusMode.Manual, Value = focusValue, DisableDriverFallback = true });

                   await captureManager.VideoDeviceController.FocusControl.FocusAsync();
               }
           }
           catch { }
       }

这样就完成了焦点获取。