Question

我正在将PDF页面转换为CanvasBitmap并在VirtualCanvasControl上绘制此图像。但每当我放大图片时，都会像素化一样。我试图渲染只是可见的部分但似乎不起作用。我做错了什么？

    <ScrollViewer Grid.RowSpan="2" 
                  Grid.Row="0" 
                  Name="PdfScrollViewer" 
                  ZoomMode="Enabled"
                  MaxZoomFactor="4"
                  MinZoomFactor="0.8"
                  HorizontalScrollBarVisibility="Visible"
                  VerticalScrollBarVisibility="Visible"
                  HorizontalAlignment="Stretch" 
                  VerticalAlignment="Stretch" 
                  BringIntoViewOnFocusChange="False">
        <canvas:CanvasVirtualControl x:Name="PageRenderCanvas" RegionsInvalidated="PageRenderCanvas_OnRegionsInvalidated"
               />
    </ScrollViewer>

RegionsInvalidated EventHandler：

private async void PageRenderCanvas_OnRegionsInvalidated(CanvasVirtualControl sender,
        CanvasRegionsInvalidatedEventArgs args)
    {
        PdfPageRenderOptions options = new PdfPageRenderOptions();
        options.DestinationWidth = (uint) (PdfScrollViewer.ActualWidth*PdfScrollViewer.ZoomFactor);
        options.DestinationHeight = (uint) (PdfScrollViewer.ActualHeight*PdfScrollViewer.ZoomFactor);
        options.SourceRect = args.VisibleRegion;

        var output = new MemoryStream().AsRandomAccessStream();
        await page.RenderToStreamAsync(output, options); // page is the PDFPage

        var image = await CanvasBitmap.LoadAsync(PageRenderCanvas, output);

        using (var ds = sender.CreateDrawingSession(args.InvalidatedRegions[0]))
        {
            ds.DrawImage(image, args.VisibleRegion);

            ds.Dispose();
        }

    }

Answer 1

图像是像素化的，因为您正在渲染位图上执行缩放由于没有关于VirtualCanvasControl和RegionsInvalidated事件的文档，我建议每次缩放更改时执行渲染，只在绘图事件中显示渲染图像。
但是，这种方法会在较大的缩放级别产生内存问题。考虑到96dpi为100％，字母页面将为816 * 1056像素，大约需要3MB。在500％变焦时，图像将为4080 * 5280像素，大约需要75MB。

在VirtualCanvasControl中缩放渲染的PDF

1 个答案: