保存WriteableBitmap

Question

"mai“是包含图像、文本和小图像的网格名称。我在博客上写了一篇文章，内容是通过WriteableBitmap (用UIelment)添加到你的图像中。

    try
    {
        WriteableBitmap wbm = new WriteableBitmap(mai, null);

        MediaLibrary ml = new MediaLibrary();
        Stream stream = new MemoryStream();

        wbm.SaveJpeg(stream, wbm.PixelWidth, wbm.PixelHeight, 0, 100);
        ml.SavePicture("mai.jpg", stream);
        MessageBox.Show("Picture Saved...");
    }
    catch (Exception ex)
    {
        MessageBox.Show(ex.Message.ToString());
    }

当我在模拟器上以调试模式运行这个程序时，我会收到一条意外错误消息。我还将这个应用程序部署到我的手机上(并将其与计算机断开连接)，并收到了同样的错误。

基本上，我试着保存一个从相机辊上选择的剪裁图像，上面覆盖了一些文本。它喜欢将这个“新”图像保存到相机滚筒中。

更新：

我也是这样做的，结果是一样的：

        WriteableBitmap wbm2 = new WriteableBitmap(mai, null);
        string tempjpeg = "tempmedicalertinfo";



        // create a virtual store and file stream. check for duplicate tempjpeg files.
        var mystore = IsolatedStorageFile.GetUserStoreForApplication();
        if (mystore.FileExists(tempjpeg))
        {
            mystore.DeleteFile(tempjpeg);
        }


        IsolatedStorageFileStream myfilestream = mystore.CreateFile(tempjpeg);

        wbm2.SaveJpeg(myfilestream, 500, 500, 0, 100);
        myfilestream.Close();

        // create a new stream from isolated storage, and save the jpeg file to the media library on windows phone.
        myfilestream = mystore.OpenFile(tempjpeg, FileMode.Open, FileAccess.Read);

        // save the image to the camera roll or saved pictures album.
        MediaLibrary library = new MediaLibrary();

        // save the image to the saved pictures album.
        try
        {
            Picture pic = library.SavePictureToCameraRoll("mai.jpg", myfilestream);
        }
        catch (Exception ex)
        {
            MessageBox.Show(ex.Message.ToString());
        }


        myfilestream.Close();

更新：

错误的堆栈跟踪：

   at Microsoft.Xna.Framework.Helpers.ThrowExceptionFromErrorCode(ErrorCodes error)
   at Microsoft.Xna.Framework.Media.MediaLibrary.SavePicture(String name, Stream source)
   at PB.MASetup.saveImage_Click(Object sender, EventArgs e)
   at Microsoft.Phone.Shell.ApplicationBarItemContainer.FireEventHandler(EventHandler handler, Object sender, EventArgs args)
   at Microsoft.Phone.Shell.ApplicationBarIconButton.ClickEvent()
   at Microsoft.Phone.Shell.ApplicationBarIconButtonContainer.ClickEvent()
   at Microsoft.Phone.Shell.ApplicationBar.OnCommand(UInt32 idCommand)
   at Microsoft.Phone.Shell.Interop.NativeCallbackInteropWrapper.OnCommand(UInt32 idCommand)

Answer 1

问题是流被定位为字节数据。因此，在将您的流传递到媒体库之前，您必须从开始时开始寻找它。这会解决你的问题。下面是一个示例：(顺便说一句，对每个IDisposable对象使用using结构是一个很好的实践)

using (MemoryStream stream = new MemoryStream())
{
    WriteableBitmap bitmap = new WriteableBitmap(LayoutRoot, null);
    bitmap.SaveJpeg(stream, bitmap.PixelWidth, bitmap.PixelHeight, 0, 100);
    stream.Seek(0, SeekOrigin.Begin);

    using (MediaLibrary mediaLibrary = new MediaLibrary())
        mediaLibrary.SavePicture("Picture.jpg", stream);
}
MessageBox.Show("Picture Saved...");

Answer 2

在经历了很多次的失败之后，我发现我的问题是缺少了WMAppManifest.xml的功能

  <Capability Name="ID_CAP_MEDIALIB" />

错误信息是如此模糊，以至于我不得不浪费大量的时间来解决这个问题。