学步园

这边我们介绍一下利用windows编程如何来画五角星，下面主要介绍了3种与五角星相关图形的画法：

1.正常的五角星

代码如下：

#include<windows.h>
#include<math.h>
#include<stdio.h>
const double PI = 3.1415926;

LRESULT CALLBACK WndProc(
  HWND hwnd,      // handle to window
  UINT uMsg,      // message identifier
  WPARAM wParam,  // first message parameter
  LPARAM lParam   // second message parameter
);

int WINAPI WinMain(
  HINSTANCE hInstance,      // handle to current instance
  HINSTANCE hPrevInstance,  // handle to previous instance
  LPSTR lpCmdLine,          // command line
  int nCmdShow              // show state
)
{
	WNDCLASS wndclass;

	wndclass.cbClsExtra = 0;
	wndclass.cbWndExtra = 0;
	wndclass.hbrBackground = (HBRUSH)GetStockObject(WHITE_BRUSH);
	wndclass.hCursor = LoadCursor(NULL, IDC_ARROW);
	wndclass.hIcon = LoadIcon(NULL, IDI_APPLICATION);
	wndclass.hInstance = hInstance;
	wndclass.lpfnWndProc = WndProc;
	wndclass.lpszClassName = "我的窗口";
	wndclass.lpszMenuName = NULL;
	wndclass.style = CS_HREDRAW | CS_VREDRAW;
	RegisterClass(&wndclass); //注册窗口类

	HWND hwnd;
	hwnd = CreateWindow("我的窗口", "窗口", WS_OVERLAPPEDWINDOW, 
		0, 0, 640, 480, NULL, NULL, hInstance, NULL);

	ShowWindow(hwnd, SW_SHOWNORMAL);
	UpdateWindow(hwnd);

	MSG Msg;
	while(GetMessage(&Msg, NULL, 0, 0))
	{
		TranslateMessage(&Msg); 
        DispatchMessage(&Msg); 
	}

	return 0;
}

LRESULT CALLBACK WndProc(
  HWND hwnd,      // handle to window
  UINT uMsg,      // message identifier
  WPARAM wParam,  // first message parameter
  LPARAM lParam   // second message parameter
)
{
	HDC hdc;
	PAINTSTRUCT ps;
	HPEN hpen;
	int r = 100;
	switch(uMsg)
	{
	case WM_PAINT:	
		hdc = BeginPaint(hwnd, &ps);
		hpen = (HPEN)GetStockObject(BLACK_PEN);
		SelectObject(hdc, hpen);

		MoveToEx(hdc, 200 , 200 - r, NULL);
		int k;
		for(k=2; k<12; k=k+2)
		{
			LineTo(hdc, (int)(200 + r * cos((90-72*k)*PI/180)), (int)(200 - r * sin((90-72*k)*PI/180)));
		}

		EndPaint(hwnd, &ps);
		DeleteObject(hpen);
		break;

	case WM_CLOSE:
		DestroyWindow(hwnd);
		break;

	case WM_DESTROY:
		PostQuitMessage(0);
	break;

	default:
		return DefWindowProc(hwnd, uMsg, wParam, lParam);
	}

	return 0;
}

2.空心的五角星

关键代码如下：

int R = 100;
	double r = R * sin(18*PI/180) / sin(54*PI/180);
	MoveToEx(hdc, 200, 200 - R, NULL);
		int k;
		for(k=1; k<6; k++)
		{
			LineTo(hdc, (int)(200 + r * cos((126-72*k)*PI/180)), (int)(200 - r*sin((126-72*k)*PI/180)));
			LineTo(hdc, (int)(200 + R * cos((90-72*k)*PI/180)), (int)(200 - R * sin((90-72*k)*PI/180)));
		}

3.带边框的五角星

关键代码如下：

	int k;
		for(k=2; k<11; k=k+2)
		{
			LineTo(hdc, (int)(200 + r * cos((90-72*k)*PI/180)), (int)(200 - r * sin((90-72*k)*PI/180)));
		}
		for(k=1; k<6; k++)
		{
			LineTo(hdc, (int)(200 + r * cos((90-72*k)*PI/180)), (int)(200 - r * sin((90-72*k)*PI/180)));
		}

4.总结：

实现画五角星最关键的是，要能够根据一个点的坐标，计算出其他所有点的坐标。剩下的画图只是简单的事情。