CODEWITHSUNDEEP
c#windows-phone-8.1win-universal-apprendertargetbitmap
lehkap
lehkap

Reputation: 56

RenderTargetBitmap without putting it on UI

I want to create a universal app in Visual Studio 2013 that creates an image from a Canvas that is generated with code dynamically. If I display the canvas on the UI (in a Grid, for example) it's alright. If I don't display the canvas, the app crashes with the message:

value does not fall within the expected range.

There is the code that i use:

Canvas cn = new Canvas();
cn.Height = 100;
cn.Width = 100;
cn.Visibility = Visibility.Visible;
Button but = new Button();
Rectangle rect = new Rectangle();
rect.Width = 100;
rect.Height = 100;
rect.Margin = new Thickness(0);
SolidColorBrush bruch = new SolidColorBrush();
bruch.Color = Colors.Blue;
rect.Fill = bruch;
but.Width = 50;
but.Height = 50;
but.Content = "23";
but.Visibility = Visibility.Visible;
cn.Children.Add(rect);
cn.Children.Add(but);
but.Margin = new Thickness(25, 25, 0, 0);
RenderTargetBitmap renderTargetBitmap = new RenderTargetBitmap();
await renderTargetBitmap.RenderAsync(cn, 100, 100);
outputImage.Source = renderTargetBitmap;

I don't want to display the canvas on the UI because I plan to use this code from a BackgroundTask.

Here is my sample project

Upvotes: 1

Views: 1129

Answers (1)

Rob Caplan - MSFT
Rob Caplan - MSFT

Reputation: 21899

Windows Phone apps can use the XamlRenderingBackgroundTask to render in a background task. C++ is recommended for the background task to keep resource usage low.

See the Updating a tile from a background task sample for an example.

XamlRenderingBackgroundTask is not supported for Windows Store apps. On Windows the RenderTargetBitmap cannot be used from a background task and requires that the target UIElement be in the main visual tree.

Upvotes: 4

Related Questions