在运行时生成的图像 [英] Generate Image at Runtime

问题描述

我想呈现在运行时的一些XAML。我的XAML是一个StringBuilder动态构建。作为一个例子，这里是一个示例：

I am trying to render some XAML at runtime. My XAML is dynamically constructed in a StringBuilder. As an example, here is a sample:

StringBuilder xaml = new StringBuilder(); 
xaml.Append("<Canvas xmlns=\"http://schemas.microsoft.com/winfx/2006/xaml/presentation\" "); 
xaml.Append("xmlns:x=\"http://schemas.microsoft.com/winfx/2006/xaml\" Height=\"135\" "); 
xaml.Append("Width=\"210\" Background=\"White\" x:Name=\"Page\">"); 

string url = "http://www.mydomain.com/images/background.png"; 
xaml.Append("<Image Width=\"300\" Height=\"200\" Canvas.Left=\"0\" Canvas.Top=\"0\" "); 
xaml.Append("x:Name=\"bgImage\" Source=\""); 
xaml.Append(url); 
xaml.Append("\" />"); 

xaml.Append("</Canvas>");

请注意此示例中的图像元素。如果我把这个XAML中的.xaml文件运行良好。如果我将其粘贴到混合，它工作正常。但是，我需要等待下载这个形象，则所呈现的XAML转换为.png。为了做到这一点，我使用下面的代码：

Please notice the Image element in this sample. If I put this XAML in a .xaml file it runs fine. If I paste it into Blend, it works fine. However, I need to wait for this image to be downloaded and then convert the rendered XAML to a .png. In order to do this, I am using the following code:

StringReader stringReader = new StringReader(xaml.ToString()); 
XmlTextReader xmlReader = new XmlTextReader(stringReader); 
FrameworkElement frameworkElement = (FrameworkElement)(XamlReader.Load(xmlReader)); 
Size availableSize = new Size(300, 200); 
frameworkElement.Measure(availableSize); 
frameworkElement.Arrange(new Rect(availableSize)); 

BitmapSource bitmap = RenderToBitmap(frameworkElement); 
PngBitmapEncoder encoder = new PngBitmapEncoder(); 
encoder.Frames.Add(BitmapFrame.Create(bitmap)); 

FileStream fileStream = new FileStream(filename, FileMode.Create); 
encoder.Save(fileStream); 
fileStream.Close();

的问题是，总是产生巴纽忽略图像元素。我猜测是因为图片来源没有下载。我如何在运行时，包括图像生成一些XAML的图像？

The problem is, the .png that is generated always ignores the Image element. I am guessing because the Image source is not downloaded. How do I generate an image from some XAML at runtime that includes an Image?

感谢您

推荐答案

为什么不直接产生在C＃中，而不是创建XAML对象，然后有运行时必须解析呢？做这种方式有以下好处：

Why not just generate the object directly in C# instead of creating XAML and then having the runtime have to parse it? Doing it that way has the following benefits:

1. 编译时你的对象的检查你现在的样子这样做，现在可能会引入，因为脂肪指法等运行时错误。


2. 更快的对象创建。直接在C＃中实例化对象会比快解析器。


3. 更易于维护。接下来的程序员一起去，并与此代码的工作将与格式良好的C＃主场迎战嵌入的XAML一个更简单的时间。


4. Refactorable。您可以重构你的C＃代码，以消除重复的代码。

1. Compile-time checking of your objects. The way you are doing it now might introduce run-time errors because of a fat-fingering, etc.
2. Faster object creation. Instantiating the objects directly in C# will be faster than the parser.
3. More maintainable. The next programmer to come along and work with this code will have an easier time with well-formatted C# vs. embedded XAML.
4. Refactorable. You can refactor your C# code to eliminate repetitive code.

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