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Tutorials MySQL & C, C++ Drawing an Ellipse with Mid Point Ellipse Algorithm in C/C++ - tutorial advance
Tutorials MySQL & C, C++ Drawing an Ellipse with Mid Point Ellipse Algorithm in C/C++ - tutorial advance
Drawing an Ellipse with Mid Point Ellipse Algorithm in C/C++
destination source:https://www.programming-techniques.com/?p=126
The theory for drawing Ellipse with Mid Point Algorithm is the same as that of Circle drawing. But the difference is that the Ellipse is divided into two regions because it has two radii. The regions are separated from each other at a point where the slope of the tangent line is –1. So we need to draw 2 regions in first quadrant and draw in other quadrant symmetrically.
The following section implements Mid – Point Ellipse Algorithm in C/C++. The source code is complied using gcc Compiler and Code::Blocks IDE. To print a pixel, SetPixel() function of windows.h is used.
Note: to run this code in your machine with Code::blocks IDE, add a link library libgdi32.a (it is usually inside MinGWlib ) in linker setting.
Source Code
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 | #include <windows.h> #include <cmath> #define ROUND(a) ((int) (a + 0.5)) /* set window handle */ static HWND sHwnd; static COLORREF redColor=RGB(255,0,0); static COLORREF blueColor=RGB(0,0,255); static COLORREF greenColor=RGB(0,255,0); void SetWindowHandle(HWND hwnd){ sHwnd=hwnd; } /* SetPixel */ void setPixel(int x,int y,COLORREF& color=redColor){ if(sHwnd==NULL){ MessageBox(NULL,"sHwnd was not initialized !","Error",MB_OK|MB_ICONERROR); exit(0); } HDC hdc=GetDC(sHwnd); SetPixel(hdc,x,y,color); ReleaseDC(sHwnd,hdc); return; } void ellipsePlotPoints(int xCenter, int yCenter, int x, int y){ setPixel(xCenter + x, yCenter + y); setPixel(xCenter - x, yCenter + y); setPixel(xCenter + x, yCenter - y); setPixel(xCenter - x, yCenter - y); } void drawEllipse(int xCenter, int yCenter, int Rx, int Ry){ int Rx2 = Rx*Rx; int Ry2 = Ry*Ry; int twoRx2 = 2 * Rx2; int twoRy2 = 2 * Ry2; int p; int x = 0; int y = Ry; int px = 0; int py = twoRx2 * y; ellipsePlotPoints(xCenter, yCenter, x, y); /* For Region 1 */ p = ROUND(Ry2 - (Rx2*Ry) + (0.25) * Rx2); while(px < py){ x++; px += twoRy2; if(p < 0){ p += Ry2 + px; }else{ y--; py -= twoRx2; p += Ry2 + px - py; } ellipsePlotPoints(xCenter, yCenter, x, y); } /* For Region 2*/ p = ROUND(Ry2 * (x + 0.5)*(x + 0.5) + Rx2 * (y - 1)*(y - 1) - Rx2 * Ry2); while(y > 0){ y--; py -= twoRx2; if(p > 0){ p += Rx2 - py; }else{ x++; px += twoRy2; p += Rx2 - py + px; } ellipsePlotPoints(xCenter, yCenter, x, y); } } /* Window Procedure WndProc */ LRESULT CALLBACK WndProc(HWND hwnd,UINT message,WPARAM wParam,LPARAM lParam){ switch(message){ case WM_PAINT: SetWindowHandle(hwnd); drawEllipse(200, 200, 100, 50); break; case WM_CLOSE: // FAIL THROUGH to call DefWindowProc break; case WM_DESTROY: PostQuitMessage(0); return 0; default: break; // FAIL to call DefWindowProc // } return DefWindowProc(hwnd,message,wParam,lParam); } int WINAPI WinMain(HINSTANCE hInstance,HINSTANCE hPrevInstance,LPSTR lpCmdLine,int iCmdShow){ static TCHAR szAppName[] = TEXT("Ellipse"); 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 ; // Register the window // if(!RegisterClass(&wndclass)){ MessageBox(NULL,"Registering the class failled","Error",MB_OK|MB_ICONERROR); exit(0); } // CreateWindow // HWND hwnd=CreateWindow(szAppName,"Mid Point Ellipse Drawing - Programming Techniques", WS_OVERLAPPEDWINDOW, CW_USEDEFAULT, CW_USEDEFAULT, CW_USEDEFAULT, CW_USEDEFAULT, NULL, NULL, hInstance, NULL); if(!hwnd){ MessageBox(NULL,"Window Creation Failed!","Error",MB_OK); exit(0); } // ShowWindow and UpdateWindow // ShowWindow(hwnd,iCmdShow); UpdateWindow(hwnd); // Message Loop // MSG msg; while(GetMessage(&msg,NULL,0,0)){ TranslateMessage(&msg); DispatchMessage(&msg); } /* return no error to the operating system */ return 0; } |
Output
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