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WPF Canvas image高分辨率打印

与其将Viewport3DVisual传递给PrintVisual方法，不如先创建一个300 DPI 的RenderTargetBitmap并调用Render方法以在位图上渲染Viewport3DVisual。然后将位图放入Image元素中，通过调用Measure和Arrange对其进行布局传递，并将Image元素传递给PrintVisual方法。

void NormalPrintOnClick(object sender, RoutedEventArgs args)
       {
           PrintDialog dlg = new PrintDialog();
 
           if (dlg.ShowDialog().GetValueOrDefault())
           {
               dlg.PrintVisual(visual3d, "PrintViewport3DVisual: 3D Cube");
           }
       }
 
       void HiResPrintOnClick(object sender, RoutedEventArgs args)
       {
           PrintDialog dlg = new PrintDialog();
 
           if (dlg.ShowDialog().GetValueOrDefault())
           {
               Rect rect = visual3d.Viewport;
 
               // Scale dimensions from 96 dpi to 600 dpi.
               double scale = 600 / 96;
 
               RenderTargetBitmap bitmap = new RenderTargetBitmap((int) (scale * (rect.Width + 1)), 
                                                                  (int) (scale * (rect.Height + 1)), 
                                                                  scale * 96, 
                                                                  scale * 96, PixelFormats.Default);
               bitmap.Render(visual3d);
 
               // Create Image element for hosting bitmap.
               Image img = new Image();
               img.Source = bitmap;
               img.Stretch = Stretch.None;
 
               // Submit Image element to layout pass so it gets finite size.
               img.Measure(new Size(dlg.PrintableAreaWidth, 
                                    dlg.PrintableAreaHeight));
               Size sizeImage = img.DesiredSize;
               img.Arrange(new Rect(new Point(0, 0), sizeImage));
 
               // Print the Image element.
               dlg.PrintVisual(img, "PrintViewport3DVisual: 3D Cube");
           }
       }

public void ExportToPng(Uri path, Image surface)
{
if (path == null) return;
 
Transform transform = surface.LayoutTransform;
surface.LayoutTransform = null;
 
System.Windows.Size size = new System.Windows.Size(surface.Width, surface.Height);
surface.Measure(size);
surface.Arrange(new Rect(size));
 
RenderTargetBitmap renderBitmap =
new RenderTargetBitmap(
(int)size.Width,
(int)size.Height,
96d,
96d,
PixelFormats.Pbgra32);
renderBitmap.Render(surface);
 
using (FileStream outStream = new FileStream(path.LocalPath, FileMode.Create))
{
PngBitmapEncoder encoder = new PngBitmapEncoder();
encoder.Frames.Add(BitmapFrame.Create(renderBitmap));
encoder.Save(outStream);
}
surface.LayoutTransform = transform;
}