在线取色器 »

« 几种典型程序Button处理代码的定位

先说下相关的API（具体含义例子代码中有注释）：

int SetMapMode(
  HDC hdc,        // handle to device context
  int fnMapMode   // new mapping mode
);

BOOL SetWindowExtEx( 
HDC hdc,       // handle to device context 
int nXExtent,  // new horizontal window extent 
int nYExtent,  // new vertical window extent 
LPSIZE lpSize  // original window extent
);

BOOL SetViewportExtEx( 
HDC hdc,       // handle to device context 
int nXExtent,  // new horizontal viewport extent 
int nYExtent,  // new vertical viewport extent 
LPSIZE lpSize  // original viewport extent
);

BOOL SetViewportOrgEx( 
HDC hdc,        // handle to device context 
int X,          // new x-coordinate of viewport origin 
int Y,          // new y-coordinate of viewport origin 
LPPOINT lpPoint // original viewport origin
);

 

 其中SetMapMode函数的fnMapMode参数（指定具体的映射方式）：

 

fnMapMode

[in] Specifies the new mapping mode. This parameter can be one of the following values.

Value	Description
MM_ANISOTROPIC	Logical units are mapped to arbitrary units with arbitrarily scaled axes. Use the SetWindowExtEx and SetViewportExtEx functions to specify the units, orientation, and scaling.
MM_HIENGLISH	Each logical unit is mapped to 0.001 inch. Positive x is to the right; positive y is up.
MM_HIMETRIC	Each logical unit is mapped to 0.01 millimeter. Positive x is to the right; positive y is up.
MM_ISOTROPIC	Logical units are mapped to arbitrary units with equally scaled axes; that is, one unit along the x-axis is equal to one unit along the y-axis. Use the SetWindowExtEx and SetViewportExtEx functions to specify the units and the orientation of the axes. Graphics device interface (GDI) makes adjustments as necessary to ensure the x and y units remain the same size (When the window extent is set, the viewport will be adjusted to keep the units isotropic).
MM_LOENGLISH	Each logical unit is mapped to 0.01 inch. Positive x is to the right; positive y is up.
MM_LOMETRIC	Each logical unit is mapped to 0.1 millimeter. Positive x is to the right; positive y is up.
MM_TEXT	Each logical unit is mapped to one device pixel. Positive x is to the right; positive y is down.
MM_TWIPS	Each logical unit is mapped to one twentieth of a printer's point (1/1440 inch, also called a twip). Positive x is to the right; positive y is up.

例子代码：

void SetIsotropic(HWND hWnd, HDC hdc)                 //将坐标系设置成笛卡尔坐标系
{
 RECT rt = GetClientRect(hWnd,&rt);                //获取窗口客户区的大小
 SetMapMode(hdc,MM_ISOTROPIC);                     //指定坐标系映射方式
 SetWindowExtEx(hdc,1000,1000,NULL);               //设置坐标系的逻辑单位 
 SetViewportExtEx(hdc,rt.right,-rt.bottom,NULL);   //设置坐标系的定义域和值域
 SetViewportOrgEx(hdc,rt.right/2,rt.bottom/2,NULL);//设置坐标系的原点坐标
}