/// <summary>
/// Internal render method
/// </summary>
/// <param name="pageNumber"></param>
/// <param name="rotationAngle"></param>
/// <returns></returns>
private async Task BackgroundPageRenderAsync()
{
using (PdfPage page = RenderedDocument.GetPage(renderedPageIndex))
{
var renderOptions = new PdfPageRenderOptions();
renderOptions.BackgroundColor = Windows.UI.Colors.Transparent;
double actualWidth = PreviewArea.ActualWidth - PreviewBorder.Margin.Left - PreviewBorder.Margin.Right - 4;
ScaledRectangle displayedPageDimension;
if (RenderedRotationAngle % 180 == 0)
{
// Raw page orientation matches displayed page orientation
displayedPageDimension = new ScaledRectangle(page.Size.Height, page.Size.Width);
}
else
{
// Raw page orientation does not match the displayed page orientation
displayedPageDimension = new ScaledRectangle(page.Size.Width, page.Size.Height);
}
double stretchedHeight = displayedPageDimension.GetScaledHeight(actualWidth);
if (stretchedHeight > MaxHeight)
{
renderOptions.DestinationHeight = (uint)(MaxHeight);
renderOptions.DestinationWidth = (uint)displayedPageDimension.GetScaledWidth(MaxHeight);
}
else
{
renderOptions.DestinationHeight = (uint)stretchedHeight;
renderOptions.DestinationWidth = (uint)actualWidth;
}
// update decent border around the previewed page
PreviewBorder.Height = renderOptions.DestinationHeight;
PreviewBorder.Width = renderOptions.DestinationWidth;
var stream = new InMemoryRandomAccessStream();
await page.RenderToStreamAsync(stream, renderOptions);
BitmapImage src = new BitmapImage();
await src.SetSourceAsync(stream);
Preview.Source = src;
RotateTransform rotationTransform = new RotateTransform()
{
Angle = RenderedRotationAngle,
CenterX = (PreviewBorder.Width - 4) / 2,
CenterY = (PreviewBorder.Height - 4) / 2
};
ScaleTransform scaleTransform;
if (RenderedRotationAngle % 180 == 0)
{
scaleTransform = new ScaleTransform()
{
ScaleX = 1,
ScaleY = 1,
};
}
else
{
scaleTransform = new ScaleTransform()
{
CenterX = (PreviewBorder.Width - 4) / 2,
CenterY = (PreviewBorder.Height - 4) / 2,
ScaleX = displayedPageDimension.AspectRatio,
ScaleY = 1 / displayedPageDimension.AspectRatio,
};
}
TransformGroup renderTransform = new TransformGroup();
renderTransform.Children.Add(rotationTransform);
renderTransform.Children.Add(scaleTransform);
Preview.RenderTransform = renderTransform;
SetBorderStyle();
}
}
