Question

如何用C++画一个圆

Answer 1

#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("SineWave");
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("This program requires Windows NT!"), szAppName, MB_ICONERROR);
return 0;
}

hwnd = CreateWindow(szAppName,
TEXT("Device Capabilities"),
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;
int iSmall;
PAINTSTRUCT ps;

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

case WM_PAINT:
hdc = BeginPaint (hwnd, &ps);
iSmall = cxClient < cyClient ? cxClient : cyClient;
Ellipse(hdc, 0, 0, iSmall, iSmall);
return 0;

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

Answer 2

1 需要opengl的类库（自己要在网上下） 其中有画圆的函数 或者调用其中的SetPixer函数 通过Bresenham算法画圆
2 利用MFC类 CDC类中有专门的画图函数

Answer 3

gdi opencv