How to save a hidden window to image in PWF

Question

I want to convert a xaml to a png image using c#. I used RenderTargetBitmap. It works quite well if the xaml that's meant to be converted is displayed in a window or a page and you can actually see it on screen. But if the window is closed or hidden, a
blank image will be generated. Does anyone know why this happens or how to make it work?

Answer 1

Hello yf11,
You can refer to the following MSDN article:
https://msdn.microsoft.com/en-us/library/aa969819(v=vs.110).aspx
How to: Encode a Visual to an Image File
// The BitmapSource that is rendered with a Visual.
RenderTargetBitmap rtb = new RenderTargetBitmap(bi.PixelWidth, bi.PixelHeight, 96, 96, PixelFormats.Pbgra32);
rtb.Render(drawingVisual);
// Encoding the RenderBitmapTarget as a PNG file.
PngBitmapEncoder png = new PngBitmapEncoder();
png.Frames.Add(BitmapFrame.Create(rtb));
using (Stream stm = File.Create("new.png"))
png.Save(stm);
In this way you can save the image at a certain time when your window is still showing.
Best regards,
Barry
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