我试图在另一个线程上渲染画布。这是我的尝试:
// returns path to exported image
private string exportToImage(double width, double height, Visual visual)
{
var filename = string.Format(@"{0}.png", Guid.NewGuid());
var tempFile = Path.Combine(tempDir, filename);
Rect rect = new Rect(0, 0, width, height);
RenderTargetBitmap rtb = new RenderTargetBitmap((int)rect.Right,
(int)rect.Bottom, 96d, 96d, System.Windows.Media.PixelFormats.Default);
Thread RENDER_THREAD = new Thread(() =>
{
this.Dispatcher.Invoke((Action)(() =>
{
rtb.Render(visual);
}));
});
RENDER_THREAD.Start();
//endcode as PNG
BitmapEncoder pngEncoder = new PngBitmapEncoder();
pngEncoder.Frames.Add(BitmapFrame.Create(rtb));
//save to memory stream
System.IO.MemoryStream ms = new System.IO.MemoryStream();
pngEncoder.Save(ms);
ms.Close();
System.IO.File.WriteAllBytes(tempFile, ms.ToArray());
return tempFile;
}
我没有收到任何错误,但渲染的结果是一个空图像。的实例是rtb
在主线程和新线程中一样吗?
Edit:
这是我的最新尝试。
我在 MouseUp 事件上创建线程:
var curLayer = GetItemsPanel((canvasDataBinding.ItemContainerGenerator.ContainerFromIndex(Binding_LayersListView.SelectedIndex)));
Thread RASTERIZE_THREAD = new Thread(() => { exportToImage(curLayer.ActualWidth, curLayer.ActualHeight, curLayer); });
RASTERIZE_THREAD.Start();
这是新线程使用的我的方法:
void exportToImage(double width, double height, Visual visual)
{
var filename = string.Format(@"{0}.png", Guid.NewGuid());
var tempFile = Path.Combine(tempDir, filename);
Rect rect = new Rect(0, 0, width, height);
RenderTargetBitmap rtb = new RenderTargetBitmap((int)rect.Right,
(int)rect.Bottom, 96d, 96d, System.Windows.Media.PixelFormats.Default);
this.Dispatcher.Invoke(new Action(() =>
{
rtb.Render(visual);
}));
//endcode as PNG
BitmapEncoder pngEncoder = new PngBitmapEncoder();
pngEncoder.Frames.Add(BitmapFrame.Create(rtb));
//save to memory stream
System.IO.MemoryStream ms = new System.IO.MemoryStream();
pngEncoder.Save(ms);
ms.Close();
System.IO.File.WriteAllBytes(tempFile, ms.ToArray());
}
那为什么它告诉我调用线程无法访问该对象,因为另一个线程拥有它 on rtb.Render(visual)
?我没有从其他任何地方调用exportToImage,那么为什么调度程序与我创建的线程没有关联?
编辑:
我需要在 Dispatcher.Invoke() 内创建 RebderTargetBitmap。