改变映射模式就可以了SetMapMode MM_ANISOTROPIC Logical units are converted to arbitrary units with arbitrarily scaled axes. Setting the mapping mode to MM_ANISOTROPIC does not change the current window or viewport settings. To change the units, orientation, and scaling, call the SetWindowExt and SetViewportExt member functions. MM_HIENGLISH Each logical unit is converted to 0.001 inch. Positive x is to the right; positive y is up. MM_HIMETRIC Each logical unit is converted to 0.01 millimeter. Positive x is to the right; positive y is up. MM_ISOTROPIC Logical units are converted to arbitrary units with equally scaled axes; that is, 1 unit along the x-axis is equal to 1 unit along the y-axis. Use the SetWindowExt and SetViewportExt member functions to specify the desired units and the orientation of the axes. GDI makes adjustments as necessary to ensure that the x and y units remain the same size. MM_LOENGLISH Each logical unit is converted to 0.01 inch. Positive x is to the right; positive y is up. MM_LOMETRIC Each logical unit is converted to 0.1 millimeter. Positive x is to the right; positive y is up. MM_TEXT Each logical unit is converted to 1 device pixel. Positive x is to the right; positive y is down. MM_TWIPS Each logical unit is converted to 1/20 of a point. (Because a point is 1/72 inch, a twip is 1/1440 inch.) Positive x is to the right; positive y is up.
void CMy34View::OnDraw(CDC* pDC)
{
CMy34Doc* pDoc = GetDocument();
ASSERT_VALID(pDoc);
if (!pDoc)
return;
CRect rect;
GetClientRect(&rect);pDC->SetMapMode(MM_ANISOTROPIC);
pDC->SetViewportOrg(rect.left,rect.bottom);
pDC->SetViewportExt(rect.right,-rect.bottom);
pDC->SetWindowExt(1000,1000);
pDC->MoveTo(10,10);
pDC->LineTo(250,10);
pDC->MoveTo(10,10);
pDC->LineTo(10,950);
}
红色部分是改坐标系的，下面的LineTo语句是画线语句。
MM_ANISOTROPIC Logical units are converted to arbitrary units with arbitrarily scaled axes. Setting the mapping mode to MM_ANISOTROPIC does not change the current window or viewport settings. To change the units, orientation, and scaling, call the SetWindowExt and SetViewportExt member functions. MM_HIENGLISH Each logical unit is converted to 0.001 inch. Positive x is to the right; positive y is up. MM_HIMETRIC Each logical unit is converted to 0.01 millimeter. Positive x is to the right; positive y is up. MM_ISOTROPIC Logical units are converted to arbitrary units with equally scaled axes; that is, 1 unit along the x-axis is equal to 1 unit along the y-axis. Use the SetWindowExt and SetViewportExt member functions to specify the desired units and the orientation of the axes. GDI makes adjustments as necessary to ensure that the x and y units remain the same size. MM_LOENGLISH Each logical unit is converted to 0.01 inch. Positive x is to the right; positive y is up. MM_LOMETRIC Each logical unit is converted to 0.1 millimeter. Positive x is to the right; positive y is up. MM_TEXT Each logical unit is converted to 1 device pixel. Positive x is to the right; positive y is down. MM_TWIPS Each logical unit is converted to 1/20 of a point. (Because a point is 1/72 inch, a twip is 1/1440 inch.) Positive x is to the right; positive y is up.
函数功能描述:该函数设置指定设备环境的映射方式，映射方式定义了将逻辑单位转换为设备单位的度量单位，并定义了设备的X、Y轴的方向。
函数原型：int SetMapMode(HDC hdc, int fnMapMode)；
hdc：指向设备环境的句柄。
fnMapMode：指定新的映射方式，此参数可以是下面列出的任何一个值。
MM_ANISOTROPIC：逻辑单位转换成具有任意比例轴的任意单位，用SetWindowExtEx和SetViewportExtEx函数可指定单位、方向和比例。
MM_HIENGLISH：每个逻辑单位转换为0.001英寸，X的正方面向右，Y的正方向向上。
MM_HIMETRIC：每个逻辑单位转换为0.01毫米，X正方向向右，Y的正方向向上。
MM_ISOTROPIC：逻辑单位转换成具有均等比例轴的任意单位，即沿X轴的一个单位等于沿Y轴的一个单位，用和函数可以指定该轴的单位和方向。图形设备界面（GDI）需要进行调整，以保证X和Y的单位保持相同大小（当设置窗口范围时，视口将被调整以达到单位大小相同）。
MM_LOENGLISH：每个逻辑单位转换为0.1英寸，X正方向向右，Y正方向向上。
MM_LOMETRIC：每个逻辑单位转换为0.1毫米，X正方向向右，Y正方向向上。
MM_TEXT：每个逻辑单位转换为一个图素，X正方向向右，Y正方向向下。
MM_TWIPS；每个逻辑单位转换为打印点的1／20（即1／1400英寸），X正方向向右，Y方向向上。
返回值：如果函数调用成功，返回值指定先前的映射方式，否则，返回值为零，若想获得更多错误信息，请调用GetLastError函数。
pDC->SetMapMode(MM_ANISOTROPIC);
pDC->SetViewportOrg(rect.left,rect.bottom);
pDC->SetViewportExt(rect.right,-rect.bottom);
pDC->SetWindowExt(1000,1000);8错。
先设置映射方式。
让后设置视口原点。
设置逻辑坐标如何转换到设备坐标。
设置窗口原点。