相机功能是手机区别于PC的一大功能，在做手机应用时，如果合理的利用了拍照功能，可能会给自己的应用增色很多。使用Windows Phone的相机功能，有两种方法，一种是使用PhotoCamera类来构建自己的相机UI，另外一种是通过CameraCaptureTask选择器来实现该功能。
他们的区别是：
- PhotoCamera类允许应用控制照片属性，如 ISO、曝光补偿和手动对焦位置，应用可以对照片有更多的控制，当然也会麻烦很多。需要实现闪光灯、对焦、分辨率、快门按钮等操作。
- CameraCaptureTask拍照会调用系统的相机功能，返回一个有照片数据的返回值，同时一旦拍照，就会进入手机相册。
一. CameraCaptureTask选择器。
- 首先需要引用
<span>using</span> Microsoft.Phone.Tasks;
- 声明任务对象，需要在页面的构造函数之前声明
CameraCaptureTask cameraCaptureTask;
在构造函数中实例化CameraCaptureTask对象，并且注册回调方法。
cameraCaptureTask = <span>new</span><span> CameraCaptureTask(); cameraCaptureTask.Completed </span>+= <span>new</span> EventHandler<PhotoResult>(cameraCaptureTask_Completed);
在应用程序中的所需位置添加以下代码，例如按键点击事件中
cameraCaptureTask.Show();
在页面中添加已完成事件处理程序的代码。此代码在用户完成任务后运行。结果是一个 PhotoResult对象，该对象公开包含图像数据的流。
<span>void</span> cameraCaptureTask_Completed(<span>object</span><span> sender, PhotoResult e)
{
</span><span>if</span> (e.TaskResult ==<span> TaskResult.OK)
{
MessageBox.Show(e.ChosenPhoto.Length.ToString());
</span><span>//</span><span>Code to display the photo on the page in an image control named myImage.
</span><span>//</span><span>System.Windows.Media.Imaging.BitmapImage bmp = new System.Windows.Media.Imaging.BitmapImage();
</span><span>//</span><span>bmp.SetSource(e.ChosenPhoto);
</span><span>//</span><span>myImage.Source = bmp;</span><span> }
}</span>
这部分比较简单，就不多讲了，给个demo吧：http://pan.baidu.com/s/1pJ0Polt
二. PhotoCamera
PhotoCamera是在windows phone os 7.1开始加入的，在使用之前需要给应用添加访问相机的权限，在
WMAppManifest.xml中添加ID_CAP_ISV_CAMERA
- 创建UI
在创建取景器时，一般会使用VideoBrush，如果需要支持横竖屏的切换，则需要加入RelativeTransform，如下代码是一个典型的相机UI
<span><!--</span><span> 相机取景器 </span><span>--></span><span><</span><span>Canvas </span><span>x:Name</span><span>="VideoCanvas"</span><span>></span><span><</span><span>Canvas.Background</span><span>></span><span><</span><span>VideoBrush </span><span>x:Name</span><span>="BackgroundVideoBrush"</span><span>></span><span><</span><span>VideoBrush.RelativeTransform</span><span>></span><span><</span><span>CompositeTransform </span><span>x:Name</span><span>="VideoBrushTransform"</span><span> CenterY</span><span>="0.5"</span><span> CenterX</span><span>="0.5"</span><span>/></span><span></</span><span>VideoBrush.RelativeTransform</span><span>></span><span></</span><span>VideoBrush</span><span>></span><span></</span><span>Canvas.Background</span><span>></span><span></</span><span>Canvas</span><span>></span>
当然你还要考虑页面上的其他元素，比如点击取景器对焦，快门、闪光灯按钮等，这些可随个人洗好自定义。
- 实现取景器和相关相机事件。
- 首先实现取景器，先判断手机有没有相关的硬件设备(背部相机(主)或者前部相机)
<span>if</span> ((PhotoCamera.IsCameraTypeSupported(CameraType.Primary) == <span>true</span>) ||<span>
(PhotoCamera.IsCameraTypeSupported(CameraType.FrontFacing) </span>== <span>true</span><span>))
{
</span><span>//</span><span> Initialize the camera, when available.</span><span>if</span><span> (PhotoCamera.IsCameraTypeSupported(CameraType.FrontFacing))
{
</span><span>//</span><span> Use front-facing camera if available.</span><span>
cam </span>= <span>new</span><span> Microsoft.Devices.PhotoCamera(CameraType.FrontFacing);
}
</span><span>else</span><span>
{
</span><span>//</span><span> Otherwise, use standard camera on back of device.</span><span>
cam </span>= <span>new</span><span> Microsoft.Devices.PhotoCamera(CameraType.Primary);
}
</span><span>//</span><span>Set the VideoBrush source to the camera.</span><span>
viewfinderBrush.SetSource(cam);
}
</span><span>else</span><span>
{
</span><span>//</span><span> The camera is not supported on the device.</span><span>this</span>.Dispatcher.BeginInvoke(<span>delegate</span><span>()
{
</span><span>//</span><span> Write message.</span><span>
txtDebug.Text </span>= <span>"</span><span>A Camera is not available on this device.</span><span>"</span><span>;
});
</span><span>//</span><span> Disable UI.</span><span>
ShutterButton.IsEnabled </span>= <span>false</span><span>;
FlashButton.IsEnabled </span>= <span>false</span><span>;
AFButton.IsEnabled </span>= <span>false</span><span>;
ResButton.IsEnabled </span>= <span>false</span><span>;
}</span>
- 在加载时也需要实现各种操作事件
<span>//</span><span> Event is fired when the PhotoCamera object has been initialized.</span><span>
cam.Initialized </span>+= <span>new</span> EventHandler<Microsoft.Devices.CameraOperationCompletedEventArgs><span>(cam_Initialized);
</span><span>//</span><span> Event is fired when the capture sequence is complete.</span><span>
cam.CaptureCompleted </span>+= <span>new</span> EventHandler<CameraOperationCompletedEventArgs><span>(cam_CaptureCompleted);
</span><span>//</span><span> Event is fired when the capture sequence is complete and an image is available.</span><span>
cam.CaptureImageAvailable </span>+= <span>new</span> EventHandler<Microsoft.Devices.ContentReadyEventArgs><span>(cam_CaptureImageAvailable);
</span><span>//</span><span> Event is fired when the capture sequence is complete and a thumbnail image is available.</span><span>
cam.CaptureThumbnailAvailable </span>+= <span>new</span> EventHandler<ContentReadyEventArgs><span>(cam_CaptureThumbnailAvailable);
</span><span>//</span><span> The event is fired when auto-focus is complete.</span><span>
cam.AutoFocusCompleted </span>+= <span>new</span> EventHandler<CameraOperationCompletedEventArgs><span>(cam_AutoFocusCompleted);
</span><span>//</span><span> The event is fired when the viewfinder is tapped (for focus).</span><span>
viewfinderCanvas.Tap </span>+= <span>new</span> EventHandler<GestureEventArgs><span>(focus_Tapped);
</span><span>//</span><span> The event is fired when the shutter button receives a half press.</span><span>
CameraButtons.ShutterKeyHalfPressed </span>+=<span> OnButtonHalfPress;
</span><span>//</span><span> The event is fired when the shutter button receives a full press.</span><span>
CameraButtons.ShutterKeyPressed </span>+=<span> OnButtonFullPress;
</span><span>//</span><span> The event is fired when the shutter button is released.</span><span>
CameraButtons.ShutterKeyReleased </span>+= OnButtonRelease;
- 上面加载了这么多事件，需要在离开此页面时释放：
<span>protected</span><span>override</span><span>void</span><span> OnNavigatingFrom(System.Windows.Navigation.NavigatingCancelEventArgs e)
{
</span><span>if</span> (cam != <span>null</span><span>)
{
</span><span>//</span><span> Dispose camera to minimize power consumption and to expedite shutdown.</span><span>
cam.Dispose();
</span><span>//</span><span> Release memory, ensure garbage collection.</span><span>
cam.Initialized </span>-=<span> cam_Initialized;
cam.CaptureCompleted </span>-=<span> cam_CaptureCompleted;
cam.CaptureImageAvailable </span>-=<span> cam_CaptureImageAvailable;
cam.CaptureThumbnailAvailable </span>-=<span> cam_CaptureThumbnailAvailable;
cam.AutoFocusCompleted </span>-=<span> cam_AutoFocusCompleted;
CameraButtons.ShutterKeyHalfPressed </span>-=<span> OnButtonHalfPress;
CameraButtons.ShutterKeyPressed </span>-=<span> OnButtonFullPress;
CameraButtons.ShutterKeyReleased </span>-=<span> OnButtonRelease;
}
}</span>
上面这些事件，看看名字估计也就懂了是干啥的了，这里说明下他们的执行顺序，CaptureThumbnailAvailable —>CaptureImageAvailable —>CaptureCompleted。
- 拍出了照片后需要保存，可以保存到相机中，使用的是SavePictureToCameraRoll方法，同时可以保存到独立存储空间中，方便以后读取(如果仅仅保存在相册中，下次读取时必须使用照片选择器让用户去选择照片)：
<span>public</span><span>void</span> cam_CaptureThumbnailAvailable(<span>object</span><span> sender, ContentReadyEventArgs e)
{
</span><span>string</span> fileName = savedCounter + <span>"</span><span>_th.jpg</span><span>"</span><span>;
</span><span>try</span><span>
{
</span><span>//</span><span> Write message to UI thread.</span><span>
Deployment.Current.Dispatcher.BeginInvoke(</span><span>delegate</span><span>()
{
txtDebug.Text </span>= <span>"</span><span>Captured image available, saving thumbnail.</span><span>"</span><span>;
});
</span><span>//</span><span> Save thumbnail as JPEG to isolated storage.</span><span>using</span> (IsolatedStorageFile isStore =<span> IsolatedStorageFile.GetUserStoreForApplication())
{
</span><span>using</span> (IsolatedStorageFileStream targetStream =<span> isStore.OpenFile(fileName, FileMode.Create, FileAccess.Write))
{
</span><span>//</span><span> Initialize the buffer for 4KB disk pages.</span><span>byte</span>[] readBuffer = <span>new</span><span>byte</span>[<span>4096</span><span>];
</span><span>int</span> bytesRead = -<span>1</span><span>;
</span><span>//</span><span> Copy the thumbnail to isolated storage.</span><span>while</span> ((bytesRead = e.ImageStream.Read(readBuffer, <span>0</span>, readBuffer.Length)) > <span>0</span><span>)
{
targetStream.Write(readBuffer, </span><span>0</span><span>, bytesRead);
}
}
}
</span><span>//</span><span> Write message to UI thread.</span><span>
Deployment.Current.Dispatcher.BeginInvoke(</span><span>delegate</span><span>()
{
txtDebug.Text </span>= <span>"</span><span>Thumbnail has been saved to isolated storage.</span><span>"</span><span>;
});
}
</span><span>finally</span><span>
{
</span><span>//</span><span> Close image stream</span><span>
e.ImageStream.Close();
}
}</span>
保存照片有两个方法：SavePicture和SavePictureToCameraRoll，前面的方法是保存到照片中心“保存的照片”中，后一种方法是保存到“本机拍照”中。
- 对于闪光灯、对焦、分辨率以及快门都有相应的方法，从上面的代码中也可以看到快门有半按、全按、释放等事件，这里不再赘述，可以从源代码中看到相关的事件。
这个例子的demo是微软提供的，比较详细，源码如下：http://pan.baidu.com/s/1c0rIqSK
参考文章：Windows Phone 的相机和照片
原文：http://www.cnblogs.com/lonelyxmas/p/3812865.html
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