windows程序设计里面，画贝塞尔曲线的程序
看到它对鼠标点击之后，重画曲线的处理方法：
首先设置画笔为白色，重画一遍（相当于把原来的擦除了）
然后更新新的坐标，把画壁设为黑色
再画一遍
觉得这真是一个新奇的思路
代码如下：
1 /*--------------------------------------- 2 BEZIER.C -- Bezier Splines Demo 3 (c) Charles Petzold, 1998 4 ---------------------------------------*/ 5 6 #include <windows.h> 7 8 LRESULT CALLBACK WndProc (HWND, UINT, WPARAM, LPARAM) ; 9 10 int WINAPI WinMain (HINSTANCE hInstance, HINSTANCE hPrevInstance, 11 PSTR szCmdLine, int iCmdShow) 12 { 13 static TCHAR szAppName[] = TEXT ("Bezier") ; 14 HWND hwnd ; 15 MSG msg ; 16 WNDCLASS wndclass ; 17 18 wndclass.style = CS_HREDRAW | CS_VREDRAW ; 19 wndclass.lpfnWndProc = WndProc ; 20 wndclass.cbClsExtra = 0 ; 21 wndclass.cbWndExtra = 0 ; 22 wndclass.hInstance = hInstance ; 23 wndclass.hIcon = LoadIcon (NULL, IDI_APPLICATION) ; 24 wndclass.hCursor = LoadCursor (NULL, IDC_ARROW) ; 25 wndclass.hbrBackground = (HBRUSH) GetStockObject (WHITE_BRUSH) ; 26 wndclass.lpszMenuName = NULL ; 27 wndclass.lpszClassName = szAppName ; 28 29 if (!RegisterClass (&wndclass)) 30 { 31 MessageBox (NULL, TEXT ("Program requires Windows NT!"), 32 szAppName, MB_ICONERROR) ; 33 return 0 ; 34 } 35 36 hwnd = CreateWindow (szAppName, TEXT ("Bezier Splines"), 37 WS_OVERLAPPEDWINDOW, 38 CW_USEDEFAULT, CW_USEDEFAULT, 39 CW_USEDEFAULT, CW_USEDEFAULT, 40 NULL, NULL, hInstance, NULL) ; 41 42 ShowWindow (hwnd, iCmdShow) ; 43 UpdateWindow (hwnd) ; 44 45 while (GetMessage (&msg, NULL, 0, 0)) 46 { 47 TranslateMessage (&msg) ; 48 DispatchMessage (&msg) ; 49 } 50 return msg.wParam ; 51 } 52 53 void DrawBezier (HDC hdc, POINT apt[]) 54 { 55 PolyBezier (hdc, apt, 4) ; 56 57 MoveToEx (hdc, apt[0].x, apt[0].y, NULL) ; 58 LineTo (hdc, apt[1].x, apt[1].y) ; 59 60 MoveToEx (hdc, apt[2].x, apt[2].y, NULL) ; 61 LineTo (hdc, apt[3].x, apt[3].y) ; 62 } 63 64 LRESULT CALLBACK WndProc (HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam) 65 { 66 static POINT apt[4] ; 67 HDC hdc ; 68 int cxClient, cyClient ; 69 PAINTSTRUCT ps ; 70 71 switch (message) 72 { 73 case WM_SIZE: 74 cxClient = LOWORD (lParam) ; 75 cyClient = HIWORD (lParam) ; 76 77 apt[0].x = cxClient / 4 ; 78 apt[0].y = cyClient / 2 ; 79 80 apt[1].x = cxClient / 2 ; 81 apt[1].y = cyClient / 4 ; 82 83 apt[2].x = cxClient / 2 ; 84 apt[2].y = 3 * cyClient / 4 ; 85 86 apt[3].x = 3 * cxClient / 4 ; 87 apt[3].y = cyClient / 2 ; 88 89 return 0 ; 90 91 case WM_LBUTTONDOWN: 92 case WM_RBUTTONDOWN: 93 case WM_MOUSEMOVE: 94 if (wParam & MK_LBUTTON || wParam & MK_RBUTTON) 95 { 96 hdc = GetDC (hwnd) ; 97 98 //擦除原来的线条 99 SelectObject (hdc, GetStockObject (WHITE_PEN)) ; 100 DrawBezier (hdc, apt) ; 101 102 if (wParam & MK_LBUTTON) 103 { 104 apt[1].x = LOWORD (lParam) ; 105 apt[1].y = HIWORD (lParam) ; 106 } 107 108 if (wParam & MK_RBUTTON) 109 { 110 apt[2].x = LOWORD (lParam) ; 111 apt[2].y = HIWORD (lParam) ; 112 } 113 114 //画出新的线条 115 SelectObject (hdc, GetStockObject (BLACK_PEN)) ; 116 DrawBezier (hdc, apt) ; 117 ReleaseDC (hwnd, hdc) ; 118 } 119 return 0 ; 120 121 case WM_PAINT: 122 InvalidateRect (hwnd, NULL, TRUE) ; 123 124 hdc = BeginPaint (hwnd, &ps) ; 125 126 DrawBezier (hdc, apt) ; 127 128 EndPaint (hwnd, &ps) ; 129 return 0 ; 130 131 case WM_DESTROY: 132 PostQuitMessage (0) ; 133 return 0 ; 134 } 135 return DefWindowProc (hwnd, message, wParam, lParam) ; 136 }