I can't understand why this doesn't work, or what I need to get it to work.
To repro, create a simple WPF application and replace the main window's constructor thusly:
public MainWindow()
{
InitializeComponent();
// simple visual definition
var grid = new Grid { Width = 300, Height = 300 };
var text = new TextBlock
{
Text = "Y DON'T I WORK???",
FontSize = 100,
FontWeight =
FontWeights.Bold
};
grid.Children.Add(text);
// update the layout so everything is awesome cool
grid.Measure(grid.DesiredSize);
grid.Arrange(new Rect(grid.DesiredSize));
grid.UpdateLayout();
// create a BitmapSource from the visual
var rtb = new RenderTargetBitmap(
(int)grid.Width,
(int)grid.Height,
96,
96,
PixelFormats.Pbgra32);
rtb.Render(grid);
// Slap it in the window
this.Content = new Image { Source = rtb, Width = 300, Height = 300 };
}
This results in an empty image. If I save the RTB to disk as a PNG its the correct size but transparent.
If, however, I do this with a visual that's been displayed on screen, it works fine.
How can I render a visual I've constructed offscreen to a bitmap?