实验4编码裁剪算法

实验4编码裁剪算法实验目的认识二维图形裁剪的原理（点的裁剪、直线的裁剪、多边形的裁剪），利用VC+OpenGL实现直线的裁剪算法。实验内容1）理解直线裁剪的原理（Cohen-Surtherland算法、梁友栋算法）2）利用VC+OpenGL实现直线的编码裁剪算法，在屏幕上用一个关闭矩形裁剪随意一条直线。3）调试、编译、改正程序。4）试试实现梁友栋裁剪算法。实验原理编码裁剪算法中，为了迅速判断一条直线段与矩形窗口的地点关系，采纳了以下图的空间区分和编码方案。裁剪一条线段时，先求出两头点所在的区号code1和code2，若code1=0且code2=0，则说明线段的两个端点均在窗口内，那么整条线段必在窗口内，应取之；若code1和code2经按位与运算的结果不为0，则说明两个端点同在窗口的上方、下方、左方或右方。这类情况下，对线段的办理是弃之。假如上述两种条件都不建立，则按第三种状况办理。求出线段与窗口某边的交点，在交点处把线段一分为二，此中必有一段完整在窗口外，可弃之，对另一段则重复上述办理。实验代码#include<GL/>#include<>#include<>#defineLEFT_EDGE1#defineRIGHT_EDGE2#defineBOTTOM_EDGE4#defineTOP_EDGE8voidLineGL(intx0,inty0,intx1,inty1){glBegin(GL_LINES);glColor3f,,;glVertex2f(x0,y0);glColor3f,,;glVertex2f(x1,y1);glEnd( );}structRectangle{floatxmin,xmax,ymin,ymax;};Rectanglerect;intx0,y0,x1,y1;intCompCode(intx,inty,Rectanglerect){//求端点所在区号intcode=0x00;if(y<code=code|4;//0100下if(y>code=code|8;//1000上if(x>code=code|2;//0010右if(x<code=code|1;//0001左returncode;}intcohensutherlandlineclip(Rectanglerect,

int

&x0,int

&y0,int

&x1,int

&y1){intaccept,done;floatx,y;accept=0;done=0;intcode0,code1,codeout;code0=CompCode(x0,y0,rect);code1=CompCode(x1,y1,rect);do{if(!(code0|code1)){//端点均在视区内accept=1;//取done=1;}elseif(code0&code1){//端点在视区外侧x0=y0=x1=y1=0;done=1;accept=1;}else{if(code0!=0){codeout=code0;}else{codeout=code1;}if(codeout&LEFT_EDGE){y=y0+(y1-y0)*/(x1-x0);//直线与视区界限的交点x=(float);}elseif(codeout&RIGHT_EDGE){y=y0+(y1-y0)*/(x1-x0);x=(float);}elseif(codeout&BOTTOM_EDGE){x=x0+(x1-x0)*/(y1-y0);y=(float);}elseif(codeout&TOP_EDGE){x=x0+(x1-x0)*/(y1-y0);y=(float);}if(codeout==code0){x0=x;y0=y;code0=CompCode(x0,y0,rect);}else{x1=x;y1=y;code1=CompCode(x1,y1,rect);}}}while(!done);if(accept){LineGL(x0,y0,x1,y1);}returnaccept;}voidmyDisplay( ){glClear(GL_COLOR_BUFFER_BIT);glColor3f,,;glRectf,,,;LineGL(x0,y0,x1,y1);glFlush( );}voidInit( ){glClearColor,,,;glShadeModel(GL_FLAT);=100;=100;=300;=300;x0=0,y0=0,x1=250,y1=86;printf("Presskey'c'toClip!\nPresskey'r'toRestore!\n"

);}voidReshape(intw,inth){glViewport(0,0,(GLsizei)w,(GLsizei)h);glMatrixMode(GL_PROJECTION);glLoadIdentity( );gluOrtho2D,(GLdouble)w,,(GLdouble)h);}voidkeyboard(unsignedcharkey,intx,inty){switch(key){case'c':cohensutherlandlineclip(rect,x0,y0,x1,y1);glutPostRedisplay( );break;case'r':Init( );glutPostRedisplay( );break;case'x':exit(0);break;default:break;}}intmain(intargc,char*argv[]){glutInit(&argc,argv);glutInitDisplayMode(GLUT_RGB|GLUT_SINGLE);glutInitWindowPosition(100,100);glutInitWindowSize(640,480);glutCreateWindow("HelloWorld!");Init( );glutDisplayFunc(myDisplay);glutReshapeFunc(Reshape);glutKeyboardFunc(keyboard);glutMainLoop( );return0;}实验结果图1裁剪前后图2裁剪前后图3裁剪前后实验剖析在上述实验