使用WriteableBitmapEx渲染TextBlock时的OutOfMemoryException

Question

我又要和OutOfMemoryException打架了。

我有在Windows Phone后台代理任务中使用WriteableBitmapEx渲染一些图像的代码片段(内存使用限制接近10M)。

下面的代码运行得很好：

Deployment.Current.Dispatcher.BeginInvoke(() =>
{
    var wbBG = BitmapFactory.New(0, 0);
    var bmp = BitmapFactory.New(0, 0);
    for (int i = 0; i < 30; i++)
    {
        using (var iso = IsolatedStorageFile.GetUserStoreForApplication())
        {
            wbBG = BitmapFactory.New(0, 0).FromContent("Assets/image" + i + ".jpg");                          
            wbBG.Invalidate();

            for (int j = 0; j < 6; j++)
            {
                bmp = BitmapFactory.New(0, 0).FromContent("Assets/" + j + ".png");
                bmp = bmp.Resize(60, 60, WriteableBitmapExtensions.Interpolation.Bilinear);

                wbBG.Blit(new Rect(j * 65, 0, 60, 60), bmp, new Rect(0, 0, 60, 60));
                wbBG.Invalidate();
            }
            string filenameBG = "/Shared/" + i + ".jpg";
            using (var stream = iso.CreateFile(filenameBG))
            {
                wbBG.SaveJpeg(stream, 480, 800, 0, 85);
                stream.Close();
            }
            wbBG = null;
            GC.Collect();
            GC.WaitForPendingFinalizers();
        }
    }
    NotifyComplete();
});

但是，如果我在循环中添加或更改为使用TextBlock，它将在使用OutOfMemoryException的第二个循环中失败

Deployment.Current.Dispatcher.BeginInvoke(() =>
{
    var wbBG = BitmapFactory.New(0, 0);
    TextBlock tb;
    for (int i = 0; i < 30; i++)
    {
        using (var iso = IsolatedStorageFile.GetUserStoreForApplication())
        {
            wbBG = BitmapFactory.New(0, 0).FromContent("Assets/image" + i + ".jpg"); 
                            //The above line would thrown OutOfMemoryException in the 2nd loop                       
            wbBG.Invalidate();

            for (int j = 0; j < 6; j++)
            {
                tb = new TextBlock(){
                    Text = j.ToString(),
                    //FontSize = 13,
                    //Height = 20,
                    //Width = 240,
                    //FontWeight = System.Windows.FontWeights.Bold,
                    //HorizontalAlignment = System.Windows.HorizontalAlignment.Center,
                    //Foreground = new SolidColorBrush(Colors.White)
                };
                wbBG.Render(tb, new TranslateTransform() { X = j*65, Y = 350 });
                wbBG.Invalidate();
                tb = null;
            }
            string filenameBG = "/Shared/" + i + ".jpg";
            using (var stream = iso.CreateFile(filenameBG))
            {
                wbBG.SaveJpeg(stream, 480, 800, 0, 85);
                stream.Close();
            }
            wbBG = null;
            GC.Collect();
            GC.WaitForPendingFinalizers();
        }
    }
    NotifyComplete();
});

你知道为什么TextBlock会导致更多的内存使用吗？

此外，我看不到有更好的方法来渲染图像上的文本。

此外，TextBlock不是IDisposable。

好吧，这是我的观点，可能是错的，我很感谢任何人的帮助，谢谢！

Answer 1

我不知道这个库，但是当资源不再使用时，您忘记了释放它们，所以试试这个：

        for (var i = 0; i < 30; i++)
        {
            using (var iso = IsolatedStorageFile.GetUserStoreForApplication())
            {
                using (var wbBG = BitmapFactory.New(0, 0).FromContent("Assets/image" + i + ".jpg"))
                {
                    wbBG.Invalidate();

                    for (int j = 0; j < 6; j++)
                    {
                        var tb = new TextBlock()
                        {
                            Text = j.ToString(),
                            //FontSize = 13,
                            //Height = 20,
                            //Width = 240,
                            //FontWeight = System.Windows.FontWeights.Bold,
                            //HorizontalAlignment = System.Windows.HorizontalAlignment.Center,
                            //Foreground = new SolidColorBrush(Colors.White)
                        };
                        wbBG.Render(tb, new TranslateTransform() { X = j * 65, Y = 350 });
                        wbBG.Invalidate();
                    }
                    using (var stream = iso.CreateFile("/Shared/" + i + ".jpg"))
                    {
                        wbBG.SaveJpeg(stream, 480, 800, 0, 85);
                    }
                }
            }
        }