C#下实现双缓冲描画高频曲线(GDI+结合GDI)

由于项目需要,要使用c#描画高频实时曲线.

但是在C#下由于描画图像使用的是GDI+,描画效率很有问题.一旦曲线太多,就会造成CPU使用率直线上升,马上飙升到100%.

在GDI+下使用双缓冲也无济于事,双缓冲本身只会解决曲线多的时候全屏闪烁问题,但描画效率还是严重低下.

其间用过多种解决方案:DRECT3D,DRIRECT2D,GDI,,,,,等等等等

最后从效率出发,最终解决方案如下:

前台显示使用GDI,而后台描画则采用GDI+

后台采用10倍于前台窗口的BUFFER,每次向其中画一条线.然后通过一个RECT视口,每次向前台显示视口里的内容.否则每次重绘的代价太高.

这个方法实现的难点主要在于GDI和GDI+的结合部分,主要代码如下:

1.函数库:using 和 WIN32API函数

1. using System.Runtime.InteropServices;
2. using System.Drawing;
3. using System.Drawing.Imaging;
4. using System.Drawing.Drawing2D;
5. using System.Drawing.Text;
7. [DllImport("gdi32")]
8. public static extern IntPtr CreateCompatibleDC(IntPtr hdc);
9. [DllImport("gdi32")]
10. public static extern IntPtr SelectObject(IntPtr hdc, IntPtr hObject);
11. [DllImport("GDI32.dll")]
12. public static extern long BitBlt(IntPtr hdcDest, int nXDest, int nYDest, int nWidth, int nHeight, IntPtr hdcSrc, int nXSrc, int nYSrc, int dwRop);
13. [DllImport("GDI32.dll")]
14. public static extern bool DeleteObject(IntPtr hObject);

2.声明对象

1. public PictureBox _backgroundGraph;//被描画的控件对象
2. //public Form _backgroundGraph;
3. public Graphics _backgroundGraphic = null; // 背景Graphic
4. public Graphics _backgroundRenderGraphic = null; // 双缓冲Graphic
5. private Graphics _backgroundMemoryGraphic = null; // 内存Graphic
6. public Graphics _backgroundDrawGraphic = null; // 描画Graphic
7. private Bitmap _backgroundMemoryBitmap = null; // 内存Bitmap
8. public BufferedGraphics _graphicsBuffer = null; // 双缓冲BufferedGraphics
9. private IntPtr _memoryGraphicHdc; // 内存Graphic适用的引用
10. private IntPtr _memoryBitmapHdc; // 内存Bitmap适用的引用

3.初始化对象

1.    public void InitDraw()
2.         {
3.             _backgroundGraph = pictureBox1;
5.             lock (_backgroundGraph)
6.             {
7.                 if (null != _backgroundGraphic)
8.                 {
9.                     _backgroundGraphic.Dispose();
10.                 }
12.                 if (null != _graphicsBuffer)
13.                 {
14.                     _graphicsBuffer.Dispose();
15.                 }
17.                 if (null != _backgroundRenderGraphic)
18.                 {
19.                     _backgroundRenderGraphic.Dispose();
20.                 }
22.                 if (null != _backgroundMemoryBitmap)
23.                 {
24.                     DeleteObject(_memoryBitmapHdc);
25.                     _backgroundMemoryBitmap.Dispose();
26.                 }
28.                 if (null != _backgroundMemoryGraphic)
29.                 {
30.                     DeleteObject(_memoryGraphicHdc);
31.                     _backgroundMemoryGraphic.Dispose();
32.                 }
34.                 if (null != _backgroundDrawGraphic)
35.                 {
36.                     _backgroundDrawGraphic.Dispose();
37.                 }
39.                 // 背景Graphic
40.                 _backgroundGraphic = _backgroundGraph.CreateGraphics();
42.                 BufferedGraphicsContext currentContext = BufferedGraphicsManager.Current;
43.                 _graphicsBuffer = currentContext.Allocate(_backgroundGraphic, _backgroundGraph.ClientRectangle);
45.                 // 双缓冲Graphic
46.                 _backgroundRenderGraphic = _graphicsBuffer.Graphics;
47.                 _backgroundRenderGraphic.Clear(Color.White);
49.                 _backgroundRenderGraphic.SetClip(_backgroundGraph.ClientRectangle);
51.                 // 内存Bitmap
52.                 _backgroundMemoryBitmap = new Bitmap(_backgroundGraph.ClientRectangle.Width * 10, _backgroundGraph.ClientRectangle.Height, _backgroundRenderGraphic);
54.                 // 内存Graphic
55.                 _backgroundMemoryGraphic = Graphics.FromImage(_backgroundMemoryBitmap);
56.                 _backgroundMemoryGraphic.Clear(Color.White);
58.                 // 创建适用的绘图区
59.                 _memoryGraphicHdc = CreateCompatibleDC(_backgroundMemoryGraphic.GetHdc());
60.                 _memoryBitmapHdc = _backgroundMemoryBitmap.GetHbitmap();
62.                 SelectObject(_memoryGraphicHdc, _memoryBitmapHdc);
64.                 // 描画Graphic
65.                 _backgroundDrawGraphic = Graphics.FromHdc(_memoryGraphicHdc);
67.                 _backgroundDrawGraphic.SmoothingMode = SmoothingMode.HighQuality;
68.                 _backgroundDrawGraphic.TextRenderingHint = TextRenderingHint.ClearTypeGridFit;
69.                 _backgroundDrawGraphic.InterpolationMode = InterpolationMode.HighQualityBilinear;
70.                 _backgroundDrawGraphic.PixelOffsetMode = PixelOffsetMode.HighQuality;
71.             }
72.         }

4.使用GDI+描画曲线

1.  public void DrawSomething()
2.         {
3.             _backgroundDrawGraphic.DrawLine(System.Drawing.Pens.Black, 0, 0, 100, 100);
5.         }

5.使用bitblt向前台描画

1.    public void UpdateView()
2.         {
3.             IntPtr memHdc = _backgroundDrawGraphic.GetHdc();
4.             IntPtr renHdc = _backgroundRenderGraphic.GetHdc();
6.             BitBlt(renHdc, 0, 0, 100,
7.             100, memHdc, 0, 0, 0xCC0020);
9.             _backgroundDrawGraphic.ReleaseHdc();
10.             _backgroundRenderGraphic.ReleaseHdc();
12.             _graphicsBuffer.Render(_backgroundGraphic);
13.         }