为 wpf WriteableBitmap 获取 DrawingContext
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Getting a DrawingContext for a wpf WriteableBitmap
提问by Emperor XLII
Is there a way to get a DrawingContext(or something similar) for a WriteableBitmap? I.e. something to allow you to call simple DrawLine/DrawRectangle/etc kinds of methods, rather than manipulate the raw pixels directly.
有没有办法获得 a DrawingContext（或类似的东西）WriteableBitmap？即允许您调用简单的DrawLine/ DrawRectangle/etc 类型的方法，而不是直接操作原始像素。
采纳答案by Emperor XLII
It appears the word is no.
看来这个词是 no。
For future reference, we plan to use a port of the Writeable Bitmap Extensionsfor WPF.
为了将来参考，我们计划使用WPF 的可写位图扩展的一个端口。
For a solution using purely existing code, any of the other suggestions mentioned below will work.
对于使用纯粹现有代码的解决方案，下面提到的任何其他建议都将起作用。
回答by Daniel Wolf
I found sixlettervariables' solution the most workable one. However, there's a "drawingContext.Close()" missing. According to MSDN, "A DrawingContext must be closed before its content can be rendered". The result is the following utility function:
我发现 Sixlettervariables 的解决方案是最可行的解决方案。但是，缺少“drawingContext.Close()”。根据 MSDN，“必须先关闭 DrawingContext，然后才能呈现其内容”。结果是以下效用函数：
public static BitmapSource CreateBitmap(
int width, int height, double dpi, Action<DrawingContext> render)
{
DrawingVisual drawingVisual = new DrawingVisual();
using (DrawingContext drawingContext = drawingVisual.RenderOpen())
{
render(drawingContext);
}
RenderTargetBitmap bitmap = new RenderTargetBitmap(
width, height, dpi, dpi, PixelFormats.Default);
bitmap.Render(drawingVisual);
return bitmap;
}
This can then easily be used like this:
然后可以像这样轻松地使用它：
BitmapSource image = ImageTools.CreateBitmap(
320, 240, 96,
drawingContext =>
{
drawingContext.DrawRectangle(
Brushes.Green, null, new Rect(50, 50, 200, 100));
drawingContext.DrawLine(
new Pen(Brushes.White, 2), new Point(0, 0), new Point(320, 240));
});
回答by Danko Durbi?
If you don't mind using System.Drawingyou could do something like:
如果您不介意使用，System.Drawing您可以执行以下操作：
var wb = new WriteableBitmap( width, height, dpi, dpi,
PixelFormats.Pbgra32, null );
wb.Lock();
var bmp = new System.Drawing.Bitmap( wb.PixelWidth, wb.PixelHeight,
wb.BackBufferStride,
PixelFormat.Format32bppPArgb,
wb.BackBuffer );
Graphics g = System.Drawing.Graphics.FromImage( bmp ); // Good old Graphics
g.DrawLine( ... ); // etc...
// ...and finally:
g.Dispose();
bmp.Dispose();
wb.AddDirtyRect( ... );
wb.Unlock();
回答by user7116
I'm wondering the same thing, as currently I do something like:
我想知道同样的事情，因为目前我做的事情是：
DrawingVisual drawingVisual = new DrawingVisual();
using (DrawingContext drawingContext = drawingVisual.RenderOpen())
{
//
// ... draw on the drawingContext
//
RenderTargetBitmap bmp = new RenderTargetBitmap(width, height, dpi, dpi, PixelFormats.Default);
bmp.Render(drawingVisual);
image.Source = bmp;
}
I'm trying to use the WriteableBitmap to allow multithreaded access to the pixel buffer, which is currently not allowed with neither a DrawingContext nor a RenderTargetBitmap. Maybe some sort of WritePixels routine based off of what you've retrieved from the RenderTargetBitmap would work?
我正在尝试使用 WriteableBitmap 来允许对像素缓冲区进行多线程访问，目前这在 DrawingContext 和 RenderTargetBitmap 中都是不允许的。也许基于您从 RenderTargetBitmap 检索到的内容的某种 WritePixels 例程会起作用？
回答by David Jeske
A different way to solve this problem is to use a RenderTargetBitmapas a backing store, just like in the WriteableBitmapexample. Then you can create and issue WPF drawing commands to it whenever you want. For example:
解决此问题的另一种方法是使用 aRenderTargetBitmap作为后备存储，就像在WriteableBitmap示例中一样。然后，您可以随时创建并向其发出 WPF 绘图命令。例如：
// create the backing store in a constructor
var backingStore =
new RenderTargetBitmap(200,200,97,97,PixelFormats.Pbgra32);
myImage.Source = backingStore;
// whenever you want to update the bitmap, do:
var drawingVisual = new DrawingVisual();
var drawingContext = drawingVisual.RenderOpen();
{
// your drawing commands go here
drawingContext.DrawRectangle(
Brushes.Red, new Pen(),
new Rect(this.RenderSize));
}
Render(drawingContext);
drawingContext.Close();
backingStore.Render(drawingVisual);
If you want to redraw this RenderTargetBitmapevery frame, you can catch the CompositionTarget.Renderingevent, like this:
如果你想RenderTargetBitmap每帧重绘这个，你可以捕捉CompositionTarget.Rendering事件，像这样：
CompositionTarget.Rendering += MyRenderingHandler;
