在程序中使用GDI+的步骤
使用之前，你必须做下面5个步骤：
（1）创建一个工程，引入GDI+头文件
#include <GdiPlus.h>
（2）使用GDI+命名空间
using namespace Gdiplus;
要不然会出现很多未定义符号的错误
（3）引入Gdiplus.lib库
#pragma comment(lib,"Gdiplus.lib")
要不然编译时会出现找不到实现的错误
（4）在使用前初始化GDI+系统资源
一般是在app类的初始化方法中
ULONG_PTR gdiplusToken;//得保证这个变量在释放GDI+资源时也能访问得到，一般设为全局变量
GdiplusStartupInput gdiplusStartupInput;
GdiplusStartup(&gdiplusToken,&gdiplusStartupInput,NULL);
（5）使用完毕后，释放GDI+系统资源
一般是在app类的析构函数中或者ExitInstance函数中或者Instance函数末尾中调用
GdiplusShutdown(gdiplusToken);
GDI+的使用：
通常，你需要创建一个Graphics对象来使用GDI+提供的各种绘图函数。
构造函数：
The Graphics class has these constructors.
| Constructor | Description |
|---|---|
| Graphics::Graphics(HDC) | Creates a Graphics::Graphics object that is associated with a specified device context. |
| Graphics::Graphics(HDC,HANDLE) | Creates a Graphics::Graphics object that is associated with a specified device context and a specified device. |
| Graphics::Graphics(HWND,BOOL) | Creates a Graphics::Graphics object that is associated with a specified window. |
| Graphics::Graphics(Image*) | Creates a Graphics::Graphics object that is associated with an Image object. |
除了上面的构造函数外，还有Graphics类提供了下面几个静态函数。它们更好用。
| Graphics::FromHDC(HDC) | The Graphics::FromHDC method creates a Graphics object that is associated with a specified device context. |
| Graphics::FromHDC(HDD,HANDLE) | The Graphics::FromHDC method creates a Graphics object that is associated with a specified device context and a specified device. |
| Graphics::FromHWND | The Graphics::FromHWND method creates a Graphics object that is associated with a specified window. |
| Graphics::FromImage | The Graphics::FromImage method creates a Graphics object that is associated with a specifiedImage object. |