Silverlight实用窍门系列：40.Silverlight中捕捉视频，截图保存到本地【附带实例源码】

         在Silverlight中我们可以捕捉视频设备以制作视频会议系统，或者通过视频设备截图功能上传头像等功能。

         下面我们通过一个简单的实例来访问视频设备，并且截取图像下载该截图文件至本地。

         一、在Silverlight运行界面中我们检查系统默认摄像头和麦克风是否可用如下图：

         二、我们看Xaml代码如下所示：

<Grid x:Name="LayoutRoot" Background="White">
<Border BorderBrush="Silver" BorderThickness="1" Height="346" HorizontalAlignment="Left"
Margin="21,19,0,0" Name="border1" VerticalAlignment="Top" Width="477" >
<Border.Background>
<VideoBrush x:Name="ShowVideo"></VideoBrush>
</Border.Background>
</Border>
<Button Content="打开摄像头" Height="32" HorizontalAlignment="Left" 
Margin="38,380,0,0" Name="button1" VerticalAlignment="Top" 
Width="95" Click="button1_Click" />
<Button Content="关闭摄像头" Height="32" HorizontalAlignment="Left"
Name="button2" Width="85" VerticalAlignment="Top" 
Margin="268,380,0,0" Click="button2_Click" />
<Button Content="截 图" Height="32" Name="button3" Margin="153,380,0,0"
HorizontalAlignment="Left" Width="91" VerticalAlignment="Top" 
Click="button3_Click" />
<StackPanel Height="346" HorizontalAlignment="Left" Margin="514,19,0,0"
Name="stackPanel1" VerticalAlignment="Top" Width="460" />
</Grid>

        在这里我们建立一个Border显示视频图像，然后加三个按钮分别控制摄像头的打开、关闭、截图。最后加一个StackPanel来显示截图的影像。

        三、下面请看CS代码如下所示，对于截图保存图片所用函数是在园子里的zhangxuguang2007兄弟那里找的。

public partial class MainPage : UserControl
{
public MainPage()
{
InitializeComponent();
}
//提供音频和视频的方法
CaptureSource video = new CaptureSource();

private void button1_Click(object sender, RoutedEventArgs e)
{
//获取计算机上的默认视频对象
VideoCaptureDevice camera = CaptureDeviceConfiguration.GetDefaultVideoCaptureDevice();
//成功请求到计算机上的视频设备
if (CaptureDeviceConfiguration.RequestDeviceAccess())
{
//设置视频设备为Camera
video.VideoCaptureDevice = camera;
//VideoBrush设置源为video
ShowVideo.SetSource(video);
ShowVideo.Stretch = Stretch.Fill;
//开始捕捉视频
video.Start();
}
}

private void button3_Click(object sender, RoutedEventArgs e)
{
//截图
WriteableBitmap wBitmap = new WriteableBitmap(border1, new MatrixTransform());
Image img = new Image();
img.Width = 450;
img.Margin = new Thickness(2);
img.Source = wBitmap;
//保存图片
if (wBitmap != null)
{
SaveFileDialog saveDlg = new SaveFileDialog();
saveDlg.Filter = "JPEG Files (*.jpeg)|*.jpeg";
saveDlg.DefaultExt = ".jpeg";

if ((bool)saveDlg.ShowDialog())
{
using (Stream fs = saveDlg.OpenFile())
{
SaveToFile(wBitmap, fs);
MessageBox.Show("图片保存成功");
}
}
}
this.stackPanel1.Children.Clear();
this.stackPanel1.Children.Add(img);
}
/// <summary>
/// 保存图片,
/// </summary>
/// <param name="bitmap"></param>
/// <param name="fs"></param>
private static void SaveToFile(WriteableBitmap bitmap, Stream fs)
{
int width = bitmap.PixelWidth;
int height = bitmap.PixelHeight;
int bands = 3;
byte[][,] raster = new byte[bands][,];

for (int i = 0; i < bands; i++)
{
raster[i] = new byte[width, height];
}

for (int row = 0; row < height; row++)
{
for (int column = 0; column < width; column++)
{
int pixel = bitmap.Pixels[width * row + column];
raster[0][column, row] = (byte)(pixel >> 16);
raster[1][column, row] = (byte)(pixel >> 8);
raster[2][column, row] = (byte)pixel;
}

}

FluxJpeg.Core.ColorModel model = new FluxJpeg.Core.ColorModel 
{ colorspace = FluxJpeg.Core.ColorSpace.RGB };
FluxJpeg.Core.Image img = new FluxJpeg.Core.Image(model, raster);


//Encode the Image as a JPEG
MemoryStream stream = new MemoryStream();
FluxJpeg.Core.Encoder.JpegEncoder encoder = 
new FluxJpeg.Core.Encoder.JpegEncoder(img, 100, stream);
encoder.Encode();

//Back to the start
stream.Seek(0, SeekOrigin.Begin);

//Get teh Bytes and write them to the stream
byte[] binaryData = new Byte[stream.Length];
long bytesRead = stream.Read(binaryData, 0, (int)stream.Length);
fs.Write(binaryData, 0, binaryData.Length);
}
private void button2_Click(object sender, RoutedEventArgs e)
{
//停止视频
video.Stop();
}
}

        四、下面我们看看实际的运行效果如何，以及保存下文档的图分别如下所示,如需源码请点击 SL4Video.zip 下载：