Render WPF Control to Image in Console App

realJSOP

I'm working on some code that will ultimately be used in a Windows service, but right now it's in a console app for easier development. I want to render a WPF TextBlock control to an image. I'm trying to use RenderTargetBitmap, and it's creating a png file on the expected dimensions, but the file is empty (well, it's 2K in size, but there's nothing in it). Can anyone tell me how to do what I'm trying to do?

".45 ACP - because shooting twice is just silly" - JSOP, 2010
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You can never have too much ammo - unless you're swimming, or on fire. - JSOP, 2010
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"Why don't you tie a kerosene-soaked rag around your ankles so the ants won't climb up and eat your candy ass." - Dale Earnhardt, 1997

Abhinav S

After reading your question, I did a search and came across this article[^]. Maybe wrapping the visual into a VisualBrush and then painting the DrawingContext is what you are looking for? The author has attached a small sample program as well.

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realJSOP

Well, that example assumes a complete WPF app, which isn't what I'm doing (remember, I'm doing a console app/windows service), but I'll see if it works...

".45 ACP - because shooting twice is just silly" - JSOP, 2010
-----
You can never have too much ammo - unless you're swimming, or on fire. - JSOP, 2010
-----
"Why don't you tie a kerosene-soaked rag around your ankles so the ants won't climb up and eat your candy ass." - Dale Earnhardt, 1997

realJSOP

No change. :(

".45 ACP - because shooting twice is just silly" - JSOP, 2010
-----
You can never have too much ammo - unless you're swimming, or on fire. - JSOP, 2010
-----
"Why don't you tie a kerosene-soaked rag around your ankles so the ants won't climb up and eat your candy ass." - Dale Earnhardt, 1997

Abhinav S

*Groan* I honestly thought this fix would help you. I wonder what the issue is? :(

Build your own survey - http://www.factile.net

Pete OHanlon

John, without the WPF rendering subsystem being involved, you won't have the necessary infrastructure in place to render out your bitmap. You are missing a Dispatcher, which means that you cannot allocate a MediaContext instance.

*pre-emptive celebratory nipple tassle jiggle* - Sean Ewington

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CodeStash - Online Snippet Management | My blog | MoXAML PowerToys | Mole 2010 - debugging made easier

realJSOP

I'm starting with xaml created in a scene editor. This xaml is comprised of just the textblock definition. I thought the problem might be because the textblok isn't in a container of any kind, so I created a canvas, and put the textblock in it before trying to render it. Here's my code:

	private readonly XNamespace \_xamlNS  = @"http://schemas.microsoft.com/winfx/2006/xaml/presentation";
	private readonly XNamespace \_sysNS   = @"clr-namespace:System;assembly=mscorlib";
	private readonly XNamespace \_xNS     = @"http://schemas.microsoft.com/winfx/2006/xaml";
	private readonly XNamespace \_localNS = @"clr-namespace:System;assembly=WpfConsoleApp";

	//--------------------------------------------------------------------------------
	public void ImagesFromText2(string folder)
	{
		foreach (DynamicContentItem item in ContentItems)
		{
			if (item.ContentType == "text")
			{
				XElement container = new XElement("Canvas", 
								new XAttribute("xmlns", \_xamlNS),
								new XAttribute("xmlns:x", \_xNS),
								new XAttribute("xmlns:local", \_localNS),
								new XAttribute("Padding", "0,0,0,0"),
								new XAttribute("Width", item.CanvasElement.Width.ToString()),
								new XAttribute("Height", item.CanvasElement.Height.ToString()));

				XElement child = item.CanvasElement.AsXElement;
				string xaml = child.ToString();

				child.Name = @"{http://clearchannel.com/spotchart/WpfConsoleApp}SpotChartTextBlock";
				//xElement.RemoveAttribute("Background");
				//xElement.RemoveAttribute("Panel.ZIndex");
				//xElement.RemoveAttribute("Canvas.Right");
				//xElement.RemoveAttribute("Canvas.Bottom");
				//xElement.RemoveAttribute("Canvas.Left");
				//xElement.RemoveAttribute("Canvas.Top");
				child.SetAttributeValue("Margin", "0,0,0,0");
				child.SetAttributeValue("xmlns", \_xamlNS);
				child.SetAttributeValue("xmlns:x", \_xNS);
				child.SetAttributeValue("xmlns:local", \_localNS);

				string text = item.LocalData;
				if (item.CanvasElement.IsDateTime)
				{
					child.SetAttributeValue("Text", item.LocalDataFormatted);
				}
				child.Name = @"{http://clearchannel.com/spotchart/WpfConsoleApp}SpotChartTextBlock.RenderTransform";
				container.Add(child);

				xaml = container.ToString();
				Canvas canvas = (Canvas)(XamlReader.Parse(xaml));
				
				SpotChartTextBlock textBlock    = (SpotChartTextBlock)(canvas.Children\[0\]);
				textBlock.VerticalTextAlignment = item.VerticalAlign;
				textBlock.SizeToFit

realJSOP

I don't want to actually see the control, I just want to render it to an image, and save it as a PNG. Should I create a WPF class library and use it from my console app? This code will ultimately be located in a Windows service.

".45 ACP - because shooting twice is just silly" - JSOP, 2010
-----
You can never have too much ammo - unless you're swimming, or on fire. - JSOP, 2010
-----
"Why don't you tie a kerosene-soaked rag around your ankles so the ants won't climb up and eat your candy ass." - Dale Earnhardt, 1997

realJSOP

I was honestly hoping it would. :)

".45 ACP - because shooting twice is just silly" - JSOP, 2010
-----
You can never have too much ammo - unless you're swimming, or on fire. - JSOP, 2010
-----
"Why don't you tie a kerosene-soaked rag around your ankles so the ants won't climb up and eat your candy ass." - Dale Earnhardt, 1997

JOAT MON

I don't think it needs a canvas. Does textBlock.Process() call the TextBlock.Measure() and TextBlock.Arrange()? I think that because you do not render to a UI, the values are not calculated, and these functions need to be explicitly called.

Jack of all trades ~ Master of none.

realJSOP

That was it. I called measure and arrange in the process method, and she wookee velly good. :)

".45 ACP - because shooting twice is just silly" - JSOP, 2010
-----
You can never have too much ammo - unless you're swimming, or on fire. - JSOP, 2010
-----
"Why don't you tie a kerosene-soaked rag around your ankles so the ants won't climb up and eat your candy ass." - Dale Earnhardt, 1997

JOAT MON

Good deal! :thumbsup:

Jack of all trades ~ Master of none.