C#下實現雙緩沖描畫高頻曲線(GDI+結合GDI)

http://blog.csdn.net/fanerde/article/details/3136670

由於項目需要,要使用c#描畫高頻實時曲線.

但是在C#下由於描畫圖像使用的是GDI+,描畫效率很有問題.一旦曲線太多,就會造成CPU使用率直線上升,馬上飆升到100%.

在GDI+下使用雙緩沖也無濟於事,雙緩沖本身只會解決曲線多的時候全屏閃爍問題,但描畫效率還是嚴重低下.

其間用過多種解決方案:DRECT3D,DRIRECT2D,GDI,,,,,等等等等

最後從效率出發,最終解決方案如下:

前台顯示使用GDI,而後台描畫則采用GDI+

後台采用10倍於前台窗口的BUFFER,每次向其中畫一條線.然後通過一個RECT視口,每次向前台顯示視口裡的內容.否則每次重繪的代價太高.

這個方法實現的難點主要在於GDI和GDI+的結合部分,主要代碼如下:
1.函數庫:using 和 WIN32API函數
using System.Runtime.InteropServices;
using System.Drawing;
using System.Drawing.Imaging;
using System.Drawing.Drawing2D;
using System.Drawing.Text;
[DllImport("gdi32")]
public static extern IntPtr CreateCompatibleDC(IntPtr hdc);
[DllImport("gdi32")]
public static extern IntPtr SelectObject(IntPtr hdc, IntPtr hObject);
[DllImport("GDI32.dll")]
public static extern long BitBlt(IntPtr hdcDest, int nXDest, int nYDest, int nWidth, int nHeight, IntPtr hdcSrc, int nXSrc, int nYSrc, int dwRop);
[DllImport("GDI32.dll")]
public static extern bool DeleteObject(IntPtr hObject);
2.聲明對象
public PictureBox _backgroundGraph;//被描畫的控件對象
//public Form _backgroundGraph;
public Graphics _backgroundGraphic = null; // 背景Graphic
public Graphics _backgroundRenderGraphic = null; // 雙緩沖Graphic
private Graphics _backgroundMemoryGraphic = null; // 內存Graphic
public Graphics _backgroundDrawGraphic = null; // 描畫Graphic
private Bitmap _backgroundMemoryBitmap = null; // 內存Bitmap
public BufferedGraphics _graphicsBuffer = null; // 雙緩沖BufferedGraphics
private IntPtr _memoryGraphicHdc; // 內存Graphic適用的引用
private IntPtr _memoryBitmapHdc; // 內存Bitmap適用的引用
3.初始化對象
public void InitDraw()
{
_backgroundGraph = pictureBox1;
lock (_backgroundGraph)
{
if (null != _backgroundGraphic)
{
_backgroundGraphic.Dispose();
}
if (null != _graphicsBuffer)
{
_graphicsBuffer.Dispose();
}
if (null != _backgroundRenderGraphic)
{
_backgroundRenderGraphic.Dispose();
}
if (null != _backgroundMemoryBitmap)
{
DeleteObject(_memoryBitmapHdc);
_backgroundMemoryBitmap.Dispose();
}
if (null != _backgroundMemoryGraphic)
{
DeleteObject(_memoryGraphicHdc);
_backgroundMemoryGraphic.Dispose();
}
if (null != _backgroundDrawGraphic)
{
_backgroundDrawGraphic.Dispose();
}
// 背景Graphic
_backgroundGraphic = _backgroundGraph.CreateGraphics();
BufferedGraphicsContext currentContext = BufferedGraphicsManager.Current;
_graphicsBuffer = currentContext.Allocate(_backgroundGraphic, _backgroundGraph.ClientRectangle);
// 雙緩沖Graphic
_backgroundRenderGraphic = _graphicsBuffer.Graphics;
_backgroundRenderGraphic.Clear(Color.White);
_backgroundRenderGraphic.SetClip(_backgroundGraph.ClientRectangle);
// 內存Bitmap
_backgroundMemoryBitmap = new Bitmap(_backgroundGraph.ClientRectangle.Width * 10, _backgroundGraph.ClientRectangle.Height, _backgroundRenderGraphic);
// 內存Graphic
_backgroundMemoryGraphic = Graphics.FromImage(_backgroundMemoryBitmap);
_backgroundMemoryGraphic.Clear(Color.White);
// 創建適用的繪圖區
_memoryGraphicHdc = CreateCompatibleDC(_backgroundMemoryGraphic.GetHdc());
_memoryBitmapHdc = _backgroundMemoryBitmap.GetHbitmap();
SelectObject(_memoryGraphicHdc, _memoryBitmapHdc);
// 描畫Graphic
_backgroundDrawGraphic = Graphics.FromHdc(_memoryGraphicHdc);
_backgroundDrawGraphic.SmoothingMode = SmoothingMode.HighQuality;
_backgroundDrawGraphic.TextRenderingHint = TextRenderingHint.ClearTypeGridFit;
_backgroundDrawGraphic.InterpolationMode = InterpolationMode.HighQualityBilinear;
_backgroundDrawGraphic.PixelOffsetMode = PixelOffsetMode.HighQuality;
}
}
4.使用GDI+描畫曲線
ublic void DrawSomething()
{
_backgroundDrawGraphic.DrawLine(System.Drawing.Pens.Black, 0, 0, 100, 100);
}
5.使用bitblt向前台描畫
public void UpdateView()
{
IntPtr memHdc = _backgroundDrawGraphic.GetHdc();
IntPtr renHdc = _backgroundRenderGraphic.GetHdc();
BitBlt(renHdc, 0, 0, 100,
100, memHdc, 0, 0, 0xCC0020);
_backgroundDrawGraphic.ReleaseHdc();
_backgroundRenderGraphic.ReleaseHdc();
_graphicsBuffer.Render(_backgroundGraphic);
}