ContentControl + RenderTargetBitmap + empty image
- by Kellls
Im trying to create some chart images without ever displaying those charts on the screen. I'v been at this for quite a while and tried a lot of different things but nothing seems to work. The code works perfectly if I display the chart in a window first, but if I don't display it in a window, the bitmap is just white with a black border (no idea why).
I have tried adding the chart to a border before rendering and giving the border a green borderBrush. In the bitmap, I see the green borderBrush then the black border and white background but no chart. I don't know where the black border is coming from as the chart is not contained in a black border.
I have tried adding the chart to a window without calling window.Show() and again just the black boarder and white background. However if I call window.Show() the bitmap contains the chart.
I have tried using a drawingVisual as explained here, same result.
Here is the code (not including adding the element to a border or window):
private static BitmapSource CreateElementScreenshot(FrameworkElement element, int dpi)
{
if (!element.IsMeasureValid)
{
Size size = new Size(element.Width, element.Height);
element.Measure(size);
element.Arrange(new Rect(size));
}
element.UpdateLayout();
var scale = dpi/96.0;
var renderTargetBitmap = new RenderTargetBitmap
(
(int)(scale * element.RenderSize.Width),(int)(scale * element.RenderSize.Height),dpi,dpi,PixelFormats.Default
);
// this is waiting for dispatcher to perform measure, arrange and render passes
element.Dispatcher.Invoke(((Action)(() => renderTargetBitmap.Render(element))), DispatcherPriority.Render);
return renderTargetBitmap;
}
Note: The chart is a ContentControl.
Is there anyway I can get the chart to render without displaying it in a window first?
