使用之前，你必須做下面5個步驟：
（1）創建一個工程，引入GDI+頭文件
#include <GdiPlus.h>
（2）使用GDI+命名空間
using namespace Gdiplus;
要不然會出現很多未定義符號的錯誤
（3）引入Gdiplus.lib庫
#pragma comment(lib,"Gdiplus.lib")
要不然編譯時會出現找不到實現的錯誤
（4）在使用前初始化GDI+系統資源
一般是在app類的初始化方法中
ULONG_PTR gdiplusToken;//得保證這個變量在釋放GDI+資源時也能訪問得到，一般設爲全局變量
GdiplusStartupInput gdiplusStartupInput;
GdiplusStartup(&gdiplusToken,&gdiplusStartupInput,NULL);
（5）使用完畢後，釋放GDI+系統資源
一般是在app類的析構函數中或者ExitInstance函數中或者Instance函數末尾中調用
GdiplusShutdown(gdiplusToken);
GDI+的使用：
通常，你需要創建一個Graphics對象來使用GDI+提供的各種繪圖函數。
構造函數：
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. |
除了上面的構造函數外，還有Graphics類提供了下面幾個靜態函數。它們更好用。
| 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. |
