{"post":"

Cohen Sutherland line clipping algorithm in C

Cohen-Sutherland line clipping is an algorithm used to determine the portion of a line that lies within a specified rectangular boundary, called a \"clipping window\". The algorithm divides the line into four regions based on its position relative to the clipping window, and then performs different operations depending on which region the line belongs to.

Code:

#include <stdio.h>\n#include <stdlib.h>\n#include <math.h>\n#include <graphics.h>\n#include <dos.h>\n\ntypedef struct coord {\n    int x, y;\n    char code[4];\n} PT;\n\nvoid drawwindow();\nvoid drawline(PT p1, PT p2);\nPT setcode(PT p);\nint visibility(PT p1, PT p2);\nPT resetendpt(PT p1, PT p2);\n\nvoid main()\n{\n    int gd = DETECT, v, gm;\n    PT p1, p2, p3, p4, ptemp;\n\n    printf(\"\\nEnter x1 and y1\\n\");\n    scanf(\"%d %d\", &p1.x, &p1.y);\n    printf(\"\\nEnter x2 and y2\\n\");\n    scanf(\"%d %d\", &p2.x, &p2.y);\n\n    initgraph(&gd, &gm, \"c:\\\\turboc3\\\\bgi\");\n    drawwindow();\n    delay(500);\n\n    drawline(p1, p2);\n    delay(500);\n    cleardevice();\n\n    delay(500);\n    p1 = setcode(p1);\n    p2 = setcode(p2);\n    v = visibility(p1, p2);\n    delay(500);\n\n    switch (v) {\n    case 0:\n        drawwindow();\n        delay(500);\n        drawline(p1, p2);\n        break;\n    case 1:\n        drawwindow();\n        delay(500);\n        break;\n    case 2:\n        p3 = resetendpt(p1, p2);\n        p4 = resetendpt(p2, p1);\n        drawwindow();\n        delay(500);\n        drawline(p3, p4);\n        break;\n    }\n\n    delay(5000);\n    closegraph();\n}\n\nvoid drawwindow()\n{\n    line(150, 100, 450, 100);\n    line(450, 100, 450, 350);\n    line(450, 350, 150, 350);\n    line(150, 350, 150, 100);\n}\n\nvoid drawline(PT p1, PT p2)\n{\n    line(p1.x, p1.y, p2.x, p2.y);\n}\n\nPT setcode(PT p) //for setting the 4 bit code\n{\n    PT ptemp;\n\n    if (p.y < 100)\n        ptemp.code[0] = '1'; //Top\n    else\n        ptemp.code[0] = '0';\n\n    if (p.y > 350)\n        ptemp.code[1] = '1'; //Bottom\n    else\n        ptemp.code[1] = '0';\n\n    if (p.x > 450)\n        ptemp.code[2] = '1'; //Right\n    else\n        ptemp.code[2] = '0';\n\n    if (p.x < 150)\n        ptemp.code[3] = '1'; //Left\n    else\n        ptemp.code[3] = '0';\n\n    ptemp.x = p.x;\n    ptemp.y = p.y;\n\n    return (ptemp);\n}\n\nint visibility(PT p1, PT p2)\n{\n    int i, flag = 0;\n\n    for (i = 0; i < 4; i++) {\n        if ((p1.code[i] != '0') || (p2.code[i] != '0'))\n            flag = 1;\n    }\n\n    if (flag == 0)\n        return (0);\n\n    for (i = 0; i < 4; i++) {\n        if ((p1.code[i] == p2.code[i]) && (p1.code[i] == '1'))\n            flag = '0';\n    }\n\n    if (flag == 0)\n        return (1);\n\n    return (2);\n}\n\nPT resetendpt(PT p1, PT p2)\n{\n    PT temp;\n    int x, y, i;\n    float m, k;\n\n    if (p1.code[3] == '1')\n        x = 150;\n\n    if (p1.code[2] == '1')\n        x = 450;\n\n    if ((p1.code[3] == '1') || (p1.code[2] == '1')) {\n        m = (float)(p2.y - p1.y) / (p2.x - p1.x);\n        k = (p1.y + (m * (x - p1.x)));\n        temp.y = k;\n        temp.x = x;\n\n        for (i = 0; i < 4; i++)\n            temp.code[i] = p1.code[i];\n\n        if (temp.y <= 350 && temp.y >= 100)\n            return (temp);\n    }\n\n    if (p1.code[0] == '1')\n        y = 100;\n\n    if (p1.code[1] == '1')\n        y = 350;\n\n    if ((p1.code[0] == '1') || (p1.code[1] == '1')) {\n        m = (float)(p2.y - p1.y) / (p2.x - p1.x);\n        k = (float)p1.x + (float)(y - p1.y) / m;\n        temp.x = k;\n        temp.y = y;\n\n        for (i = 0; i < 4; i++)\n            temp.code[i] = p1.code[i];\n\n        return (temp);\n    }\n    else\n        return (p1);\n}\n

Output:

Enter x1 and y1\n100\n100\n\nEnter x2 and y2\n200\n200\n

Before and After Clipping:

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