http://blog.csdn.net/cnming/archive/2007/04/21/1574030.aspx
由于内存释放问题，使用BitBlt方法会导致内存占用慢慢长大而不会被释放，使用普通的双缓冲没有这个问题，而且速度可以
由于是裁剪了部分代码，因此存在代码不完整的问题
Cementing.CurveSplit.DrawCurvePress 再memDC指向的位图（memBmp）上画压力曲线图，其它类似
using System;
using System.Collections.Generic;
using System.Text;
using System.Runtime.InteropServices;
namespace Cementing
{
class Win32Support
{
/// <summary>
/// Enumeration to be used for those Win32 function that return BOOL
/// </summary>
public enum Bool
{
False = 0,
True
};
/// <summary>
/// Enumeration for the raster operations used in BitBlt.
/// In C++ these are actually #define. But to use these
/// constants with C#, a new enumeration type is defined.
/// </summary>
public enum TernaryRasterOperations
{
SRCCOPY = 0x00CC0020, /* dest = source */
SRCPAINT = 0x00EE0086, /* dest = source OR dest */
SRCAND = 0x008800C6, /* dest = source AND dest */
SRCINVERT = 0x00660046, /* dest = source XOR dest */
SRCERASE = 0x00440328, /* dest = source AND (NOT dest ) */
NOTSRCCOPY = 0x00330008, /* dest = (NOT source) */
NOTSRCERASE = 0x001100A6, /* dest = (NOT src) AND (NOT dest) */
MERGECOPY = 0x00C000CA, /* dest = (source AND pattern) */
MERGEPAINT = 0x00BB0226, /* dest = (NOT source) OR dest */
PATCOPY = 0x00F00021, /* dest = pattern */
PATPAINT = 0x00FB0A09, /* dest = DPSnoo */
PATINVERT = 0x005A0049, /* dest = pattern XOR dest */
DSTINVERT = 0x00550009, /* dest = (NOT dest) */
BLACKNESS = 0x00000042, /* dest = BLACK */
WHITENESS = 0x00FF0062, /* dest = WHITE */
};
/// <summary>
/// CreateCompatibleDC
/// </summary>
[DllImport("gdi32.dll", ExactSpelling = true, SetLastError = true)]
public static extern IntPtr CreateCompatibleDC(IntPtr hDC);
/// <summary>
/// DeleteDC
/// </summary>
[DllImport("gdi32.dll", ExactSpelling = true, SetLastError = true)]
public static extern Bool DeleteDC(IntPtr hdc);
/// <summary>
/// SelectObject
/// </summary>
[DllImport("gdi32.dll", ExactSpelling = true)]
public static extern IntPtr SelectObject(IntPtr hDC, IntPtr hObject);
/// <summary>
/// DeleteObject
/// </summary>
[DllImport("gdi32.dll", ExactSpelling = true, SetLastError = true)]
public static extern Bool DeleteObject(IntPtr hObject);
/// <summary>
/// CreateCompatibleBitmap
/// </summary>
[DllImport("gdi32.dll", ExactSpelling = true, SetLastError = true)]
public static extern IntPtr CreateCompatibleBitmap(IntPtr hObject, int width, int height);
/// <summary>
/// BitBlt
/// </summary>
[DllImport("gdi32.dll", ExactSpelling = true, SetLastError = true)]
public static extern Bool BitBlt(IntPtr hObject, int nXDest, int nYDest, int nWidth, int nHeight, IntPtr hObjSource, int nXSrc, int nYSrc, TernaryRasterOperations dwRop);
}
}