我正在使用microsoft的PrintHelper（microsoft.Toolkit.Uwp.Helpers.PrintHelper）为我的应用程序打印pdf。现在，通过将pdf渲染到BitmapImage中并由此打印BitmapImage来实际进行打印。这对于少数页面来说效果很好。但是，当页面数量增加时，用于渲染BitmapImages的内存消耗将变高。尽管我使用垃圾回收，但是打印操作后内存不会释放。当执行多次打印时，该应用程序将崩溃。

有什么方法可以减少内存泄漏或提高打印效率？

这是我的代码：

在此函数GetImages()返回BitmapImages。 PrintPreview是显示BitmapImages的网格。

    public async Task PrintAsync()
    {
        GC.Collect();
        foreach (var image in await GetImages())
        {
            Grid grid = new Grid();
            var printpreview = new PrintPreview(image);
            grid.Children.Add(printpreview);

            printHelper.AddFrameworkElementToPrint(grid); printpreview = null;
            grid = null;
            GC.Collect();
        }
    }

即使我在打印操作后强行收集GC，也不会释放内存。

    private void PrintHelper_OnPrintSucceeded()
    {
        GC.Collect();
        printHelper.ClearListOfPrintableFrameworkElements();
        printHelper.Dispose();
        GC.suppressfinalize(this);

    }

编辑：

下面是GetImages（）函数。

    public async Task<IEnumerable<ImageSource>> GetImages(int qualityRatio = 2)
    {
        GC.Collect();
        if (pdf_stream != null)
        {
            StorageFolder myfolder = ApplicationData.Current.LocalFolder;
            StorageFile pdf_file;
            pdf_file = await myfolder.CreateFileAsync(filename + ".pdf",CreationCollisionOption.GenerateUniqueName);
            using (Stream outputStream = await pdf_file.OpenStreamForWriteAsync())
            {
                await pdf_stream.AsStreamForRead().CopyToAsync(outputStream);
            }
            var result = new List<ImageSource>();
            try
            {
                var document = await PdfDocument.LoadFromFileAsync(pdf_file);
                for (uint i = 0; i < document.PageCount; i++)
                {
                    using (var page = document.GetPage(i))
                    {
                        using (var memoryStream = new MemoryStream())
                        {
                            using (var randomStream = memoryStream.AsRandomaccessStream())
                            {
                                var image = new BitmapImage();
                                var options = new PdfPageRenderOptions
                                {
                                    DestinationWidth = (uint)page.Size.Width * (uint)qualityRatio,DestinationHeight = (uint)page.Size.Height * (uint)qualityRatio
                                };
                                await page.RenderToStreamAsync(randomStream,options);
                                image.Setsource(randomStream);
                                result.Add(image);
                            }
                        }
                    }
                }
            }
            catch { }
            return result;
        }
        return null;
    }

PrintPreview.xaml

<Page
x:Class="App.src.PrintPreview"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
mc:Ignorable="d"
Background="{ThemeResource ApplicationPageBackgroundThemeBrush}">

<Grid>
    <Image Source="{Binding}"   Stretch="Uniform" Margin="0"></Image>
</Grid>

PrintPreview.xaml.cs

public sealed partial class PrintPreview : Page
{
    public PrintPreview(ImageSource image)
    {
        this.InitializeComponent();
        this.DataContext = image;
    }
}