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Windows Phone 开发——相机功能开发

2024-07-10 00:00:59   223人阅读

原文:Windows Phone 开发——相机功能开发

　　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。

  1. 首先需要引用
using Microsoft.Phone.Tasks;

 

  1. 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 = new CameraCaptureTask();cameraCaptureTask.Completed += new 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。

void cameraCaptureTask_Completed(object sender, PhotoResult e){    if (e.TaskResult == TaskResult.OK)    {        MessageBox.Show(e.ChosenPhoto.Length.ToString());//Code to display the photo on the page in an image control named myImage.        //System.Windows.Media.Imaging.BitmapImage bmp = new System.Windows.Media.Imaging.BitmapImage();        //bmp.SetSource(e.ChosenPhoto);        //myImage.Source = bmp;    }}

 

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

 

  1. 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

<!-- 相机取景器 -->        <Canvas x:Name="VideoCanvas">            <Canvas.Background>                <VideoBrush x:Name="BackgroundVideoBrush" >                    <VideoBrush.RelativeTransform>                        <CompositeTransform x:Name="VideoBrushTransform" CenterY="0.5" CenterX="0.5"/>                    </VideoBrush.RelativeTransform>                </VideoBrush>            </Canvas.Background>        </Canvas>

 

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。

 

  1. 实现取景器和相关相机事件。
    1. 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)
if ((PhotoCamera.IsCameraTypeSupported(CameraType.Primary) == true) ||                 (PhotoCamera.IsCameraTypeSupported(CameraType.FrontFacing) == true))            {                // Initialize the camera, when available.                if (PhotoCamera.IsCameraTypeSupported(CameraType.FrontFacing))                {                    // Use front-facing camera if available.                    cam = new Microsoft.Devices.PhotoCamera(CameraType.FrontFacing);                }                else                {                    // Otherwise, use standard camera on back of device.                    cam = new Microsoft.Devices.PhotoCamera(CameraType.Primary);                }    //Set the VideoBrush source to the camera.                viewfinderBrush.SetSource(cam);            }            else            {                // The camera is not supported on the device.                this.Dispatcher.BeginInvoke(delegate()                {                    // Write message.                    txtDebug.Text = "A Camera is not available on this device.";                });                 // Disable UI.                ShutterButton.IsEnabled = false;                FlashButton.IsEnabled = false;                AFButton.IsEnabled = false;                ResButton.IsEnabled = false;            }

 

  1. 在加载时也需要实现各种操作事件
// Event is fired when the PhotoCamera object has been initialized.                cam.Initialized += new EventHandler<Microsoft.Devices.CameraOperationCompletedEventArgs>(cam_Initialized);                 // Event is fired when the capture sequence is complete.                cam.CaptureCompleted += new EventHandler<CameraOperationCompletedEventArgs>(cam_CaptureCompleted);                 // Event is fired when the capture sequence is complete and an image is available.                cam.CaptureImageAvailable += new EventHandler<Microsoft.Devices.ContentReadyEventArgs>(cam_CaptureImageAvailable);                 // Event is fired when the capture sequence is complete and a thumbnail image is available.                cam.CaptureThumbnailAvailable += new EventHandler<ContentReadyEventArgs>(cam_CaptureThumbnailAvailable);                 // The event is fired when auto-focus is complete.                cam.AutoFocusCompleted += new EventHandler<CameraOperationCompletedEventArgs>(cam_AutoFocusCompleted);                 // The event is fired when the viewfinder is tapped (for focus).                viewfinderCanvas.Tap += new EventHandler<GestureEventArgs>(focus_Tapped);                 // The event is fired when the shutter button receives a half press.                CameraButtons.ShutterKeyHalfPressed += OnButtonHalfPress;                 // The event is fired when the shutter button receives a full press.                CameraButtons.ShutterKeyPressed += OnButtonFullPress;                 // The event is fired when the shutter button is released.                CameraButtons.ShutterKeyReleased += OnButtonRelease;

 

  1. 上面加载了这么多事件，需要在离开此页面时释放：
protected override void OnNavigatingFrom(System.Windows.Navigation.NavigatingCancelEventArgs e)        {            if (cam != null)            {                // Dispose camera to minimize power consumption and to expedite shutdown.                cam.Dispose();                 // Release memory, ensure garbage collection.                cam.Initialized -= cam_Initialized;                cam.CaptureCompleted -= cam_CaptureCompleted;                cam.CaptureImageAvailable -= cam_CaptureImageAvailable;                cam.CaptureThumbnailAvailable -= cam_CaptureThumbnailAvailable;                cam.AutoFocusCompleted -= cam_AutoFocusCompleted;                CameraButtons.ShutterKeyHalfPressed -= OnButtonHalfPress;                CameraButtons.ShutterKeyPressed -= OnButtonFullPress;                CameraButtons.ShutterKeyReleased -= OnButtonRelease;            }        }

 

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。

 

  1. 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)：
public void cam_CaptureThumbnailAvailable(object sender, ContentReadyEventArgs e)        {            string fileName = savedCounter + "_th.jpg";             try            {                // Write message to UI thread.                Deployment.Current.Dispatcher.BeginInvoke(delegate()                {                    txtDebug.Text = "Captured image available, saving thumbnail.";                });                 // Save thumbnail as JPEG to isolated storage.                using (IsolatedStorageFile isStore = IsolatedStorageFile.GetUserStoreForApplication())                {                    using (IsolatedStorageFileStream targetStream = isStore.OpenFile(fileName, FileMode.Create, FileAccess.Write))                    {                        // Initialize the buffer for 4KB disk pages.                        byte[] readBuffer = new byte[4096];                        int bytesRead = -1;                         // Copy the thumbnail to isolated storage.                        while ((bytesRead = e.ImageStream.Read(readBuffer, 0, readBuffer.Length)) > 0)                        {                            targetStream.Write(readBuffer, 0, bytesRead);                        }                    }                }                 // Write message to UI thread.                Deployment.Current.Dispatcher.BeginInvoke(delegate()                {                    txtDebug.Text = "Thumbnail has been saved to isolated storage.";                 });            }            finally            {                // Close image stream                e.ImageStream.Close();            }        }

 

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。

 

  1. 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


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