Question

已知圆心与半径画圆，用c++实现（mfc）

比如半径为5，圆心坐标为（1,2），完整的程序与解释

Answer 1

MFC就是API的封装。
当然也可以自己写库，那个就是调系统的DLL，总之自己操作显卡是吃不消的。
不同的显卡你要不同代码……你吃得消？还是把这些细节交给系统，…
调API的代价低，也简单。

MoveToEx(hdc,xBeg,xBeg,NULL);
LineTo(hdc,xEnd,yEnd)//直线
Arc(hdc,xLeft,yTop,xRignt,yBottom,xStart,yStart,xEnd,yEnd);//弧
Rectangle(hdc,xLeft,yTop,xRignt,yBottom);//矩形
Ellipse(hdc,xLeft,yTop,xRignt,yBottom);//圆或者椭圆
这些大致就是基本几何图形的函数吧，，，，还有很多的可以去查。
具体的代码贴上，这是《windows程序设计》里面的代码，稍微有点过时，不过依然好用。
#include <windows.h>

LRESULT CALLBACK WndProc (HWND, UINT, WPARAM, LPARAM) ;

int WINAPI WinMain (HINSTANCE hInstance, HINSTANCE hPrevInstance,
PSTR szCmdLine, int iCmdShow)
{
static TCHAR szAppName[] = TEXT ("LineDemo") ;
HWND hwnd ;
MSG msg ;
WNDCLASS wndclass ;

wndclass.style = CS_HREDRAW | CS_VREDRAW ;
wndclass.lpfnWndProc = WndProc ;
wndclass.cbClsExtra = 0 ;
wndclass.cbWndExtra = 0 ;
wndclass.hInstance = hInstance ;
wndclass.hIcon = LoadIcon (NULL, IDI_APPLICATION) ;
wndclass.hCursor = LoadCursor (NULL, IDC_ARROW) ;
wndclass.hbrBackground = (HBRUSH) GetStockObject (WHITE_BRUSH) ;
wndclass.lpszMenuName = NULL ;
wndclass.lpszClassName = szAppName ;

if (!RegisterClass (&wndclass))
{
MessageBox (NULL, TEXT ("Program requires Windows NT!"),
szAppName, MB_ICONERROR) ;
return 0 ;
}

hwnd = CreateWindow (szAppName, TEXT ("Line Demonstration"),
WS_OVERLAPPEDWINDOW,
CW_USEDEFAULT, CW_USEDEFAULT,
CW_USEDEFAULT, CW_USEDEFAULT,
NULL, NULL, hInstance, NULL) ;

ShowWindow (hwnd, iCmdShow) ;
UpdateWindow (hwnd) ;

while (GetMessage (&msg, NULL, 0, 0))
{
TranslateMessage (&msg) ;
DispatchMessage (&msg) ;
}
return msg.wParam ;
}

LRESULT CALLBACK WndProc (HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
{
static int cxClient, cyClient ;
HDC hdc ;
PAINTSTRUCT ps ;

switch (message)
{
case WM_SIZE:
cxClient = LOWORD (lParam) ;
cyClient = HIWORD (lParam) ;
return 0 ;

case WM_PAINT:
hdc = BeginPaint (hwnd, &ps) ;

Rectangle (hdc, cxClient / 8, cyClient / 8,
7 * cxClient / 8, 7 * cyClient / 8) ;

MoveToEx (hdc, 0, 0, NULL) ;
LineTo (hdc, cxClient, cyClient) ;

MoveToEx (hdc, 0, cyClient, NULL) ;
LineTo (hdc, cxClient, 0) ;

Ellipse (hdc, cxClient / 8, cyClient / 8,
7 * cxClient / 8, 7 * cyClient / 8) ;

RoundRect (hdc, cxClient / 4, cyClient / 4,
3 * cxClient / 4, 3 * cyClient / 4,
cxClient / 4, cyClient / 4) ;

EndPaint (hwnd, &ps) ;
return 0 ;

case WM_DESTROY:
PostQuitMessage (0) ;
return 0 ;
}
return DefWindowProc (hwnd, message, wParam, lParam) ;
}

希望有用。

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不要复制-粘贴好不，不过还是感谢你回答