Render a hidden canvas without showing it?

Question

I want to store a canvas on disk as a PNG image.

This works when the canvas is completely shown using this code:

RenderTargetBitmap rtb = new RenderTargetBitmap(794, 1122, 96d, 96d, System.Windows.Media.PixelFormats.Default);
rtb.Render(canvas);

But parts that are not shown at that time are not rendered. When the visual is not shown at all, nothing is rendered.

Then how can I save Canvas build in code to disc without showing it?

No, it doesn't. It's the same code I currently use. UpdateLayout() didn't fix it either — Tiele Declercq, Oct 22 '15 at 11:45
Only solution I can come up with is to put my Canvas in a FlowDocument and save this. — Tiele Declercq, Oct 22 '15 at 11:46
The canvas has to get a layout, [see here](http://stackoverflow.com/a/14953281/1136211). — Clemens, Oct 22 '15 at 12:10
Measure() and Arrange() did the trick. But my PNG still is mainly black. Is seems that it's not using my white background brush of the canvas..? — Tiele Declercq, Oct 22 '15 at 12:29

score 3 · Accepted Answer · answered Oct 22 '15 at 13:10

3

Okay, I've got it fixed with the help of heltonbiker & Clemens.

var size = new Size(794, 122);
Document.Measure(size);
Document.Arrange(new Rect(size));

Document.UpdateLayout();

RenderTargetBitmap rtb = new RenderTargetBitmap(794, 1122, 96d, 96d, System.Windows.Media.PixelFormats.Default);
rtb.Render(Document);

But when I save my canvas to disc it had a black background. I solved this by adding a Rectangle to my XAML inside the Canvas.

answered Oct 22 '15 at 13:10

Tiele Declercq

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The answer code does is not complete and it's hard to get the idea. – JM217 Sep 15 '19 at 11:03

Render a hidden canvas without showing it?

1 Answers1