在程序中使用GDI+的步骤

Posted 2022-06-21 善良超锅锅

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.