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Tutorials MySQL & C, C++ Cohen-Sutherland Line Clipping Algorithm with C/C++ - tutorial advance
Tutorials MySQL & C, C++ Cohen-Sutherland Line Clipping Algorithm with C/C++ - tutorial advance
Cohen-Sutherland Line Clipping Algorithm with C/C++
destination source:https://www.programming-techniques.com/?p=93
Theory
In this method, every line endpoint is assigned a four-digit binary code(region code) that identifies the location of the point relative to the boundary.
b1 : left
b2 : right
b3 : below
b4 : above
b1 : left
b2 : right
b3 : below
b4 : above
The value 1 indicates its relative position. If a point is within clipping rectangle then region code is 0000. So,
If x – xwmin < 0 , b1 = 1
If xwmax – x < 0 , b2 = 1
If y – ywmin < 0 , b3 = 1
If ywmin – y < 0 , b4 = 1
If the region codes of both end points are 0000 then we accept
the line. Any line that have one in the same bit position is rejected i.e If RA AND RB ? 0 ,line is completely outside.
If x – xwmin < 0 , b1 = 1
If xwmax – x < 0 , b2 = 1
If y – ywmin < 0 , b3 = 1
If ywmin – y < 0 , b4 = 1
If the region codes of both end points are 0000 then we accept
the line. Any line that have one in the same bit position is rejected i.e If RA AND RB ? 0 ,line is completely outside.
The lines which can not be identified as completely inside or outside a window by these tests are checked for intersection with the window boundary. Such lines may or may not cross into the window interior.
Source Code
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.
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 | #include <windows.h> #include <cmath> #define ROUND(a) ((int) (a + 0.5)) #define LEFT_EDGE 0x1 #define RIGHT_EDGE 0x2 #define BOTTOM_EDGE 0x4 #define TOP_EDGE 0x8 #define INSIDE(a) (!a) #define REJECT(a,b) (a&b) #define ACCEPT(a,b) (!(a|b)) /* 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); typedef struct Point { int x; int y; }pt; pt winMin = {100, 100}; pt winMax = {800, 400}; pt p1 = {200, 200}; pt p2 = {900, 300}; 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 LineBresenham (int xa, int ya, int xb, int yb){ int dx = (xb - xa), dy = (yb - ya); int x, y, xEnd, yEnd; int p = 2 * abs(dy) - abs(dx); int twoDy = 2 * abs(dy), twoDyDx = 2 * (abs(dy) - abs(dx)); int tFactor = dx*dy; if(xa > xb){ x = xb; y = yb; xEnd = xa; }else{ x = xa; y = ya; xEnd = xb; } setPixel(x, y); while(x < xEnd){ x++; if(p < 0) p += twoDy; else{ if(tFactor > 0) //for positive slope y++; else //for negative slope y--; p += twoDyDx; } setPixel(x, y); } } void drawBoundary(pt winMin, pt winMax){ int x, y; x = winMin.x; for(y = winMin.y; y < winMax.y; y++){ setPixel(x,y, blueColor); } y = winMin.y; for(x = winMin.x; x < winMax.x; x++){ setPixel(x,y, blueColor); } x = winMax.x; for(y = winMin.y; y < winMax.y; y++){ setPixel(x,y, blueColor); } y = winMax.y; for(x = winMin.x; x < winMax.x; x++){ setPixel(x,y, blueColor); } } unsigned char encode(pt Point, pt winMin, pt winMax){ unsigned char code = 0x00; if(Point.x < winMin.x) code = code | LEFT_EDGE; if(Point.x > winMax.x) code = code | RIGHT_EDGE; if(Point.y < winMin.y) code = code | BOTTOM_EDGE; if(Point.y > winMax.y) code = code | TOP_EDGE; return (code); } void swapPts(pt *p1, pt *p2){ pt temp; temp = *p1; *p1 = *p2; *p2 = temp; } void swapCodes (unsigned char *c1, unsigned char *c2){ unsigned char temp; temp = *c1; *c1 = *c2; *c2 = temp; } void clipLine (pt winMin, pt winMax, pt p1, pt p2){ unsigned char code1, code2; int done = FALSE, draw = FALSE; float m; while(!done){ code1 = encode (p1, winMin, winMax); code2 = encode (p2, winMin, winMax); if(ACCEPT(code1, code2)){ done = TRUE; draw = TRUE; } else if(REJECT (code1, code2)) done = TRUE; else{ if (INSIDE(code1)){ swapPts(&p1, &p2); swapCodes (&code1, &code2); } if(p2.x != p1.x) m = (p2.y - p1.y) / (p2.x - p1.x); if(code1 & LEFT_EDGE){ p1.y += (winMin.x - p1.x) * m; p1.x = winMin.x; }else if(code1 & RIGHT_EDGE){ p1.y += (winMax.x - p1.x) * m; p1.x = winMax.x; }else if(code1 & BOTTOM_EDGE){ if(p2.x != p1.x) p1.x += (winMin.y - p1.y) / m; p1.y = winMin.y; }else if(code1 & TOP_EDGE){ if(p2.x != p1.x) p1.x += (winMax.y - p1.y)/m; p1.y = winMax.y; } } } if(draw){ LineBresenham(ROUND(p1.x), ROUND(p1.y), ROUND(p2.x), ROUND(p2.y)); } } /* Window Procedure WndProc */ LRESULT CALLBACK WndProc(HWND hwnd,UINT message,WPARAM wParam,LPARAM lParam){ switch(message){ case WM_PAINT: SetWindowHandle(hwnd); drawBoundary(winMin, winMax); clipLine(winMin, winMax, p1, p2 ); 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("Line Clipping"); 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,"Cohen Sutherland Algorithm - 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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