裁剪参考代码.doc

参考代码：1、直线的裁剪 SutherlandCohen算法Sutherland_Cohen(float x0, float y0, float x2, float y2)unsigned int c,c1,c2; float x,y,wx,wy; bool accept=false, done=false; c1=EnCode(x0,y0); c2=EnCode(x2,y2); do if (c1|c2)=0) accept=true; done=true; else if(c1&c2)!=0)done=true; else c=c1; if(c=0) c=c2; /求位于窗口外的点 wx=x2-x0; wy=y2-y0; if (c&8)=8) x=x0+wx*(wyt-y0)/wy; y=wyt; else if (c&4)=4) x=x0+wx*(wyb-y0)/wy; y=wyb; else if (c&1)=1) y=y0+wy*(wxl-x0)/wx; x=wxl; else y=y0+wy*(wxr-x0)/wx; x=wxr; if (c = c1) /表明c1!=0,起始点不在窗口内，将交点作为新的起点重复判断步骤； x0 = x; y0 = y; c1 = EnCode(x0, y0); else /终点不在窗口内，交点作为新的终点 x2 = x; y2 = y; c2 = EnCode(x2, y2); while(done=false); if (accept=true) drawLine(int(x0), int(y0), int(x2), int(y2)/绘制裁剪出的线段 EnCode(float LinePx, float LinePy)unsigned int RC=0;if(LinePxwxr)RC=RC | RIGHT;if(LinePywyt)RC=RC | TOP;return RC; 中点分割算法MidPoint(float xx0, float yy0, float xx2, float yy2)int RC0,RC1,RC;float x,y;bool accept=false;RC0=EnCode(xx0,yy0);RC1=EnCode(xx2,yy2);if(RC0|RC1)=0)/简取之accept=true; else if(RC0&RC1)!=0)/简弃之 accept=false;return;elseif(RC0=0|RC1=0)/一个顶点在窗口里面，一个顶点在窗口外面if(RC0=0)/P0点在窗口内，P1点在窗口外MidClip(xx0,yy0,&xx2,&yy2,true);else/P1点在窗口内，P0点在窗口外MidClip(xx2,yy2,&xx0,&yy0,false);else/两个点都在窗口外面，将进行拆分，始终可以拆分成两段直线。离P0点近的为false,离P1点近的为truex=(xx0+xx2)/2;y=(yy0+yy2)/2;RC=EnCode(x,y);while(RC!=0)/中点落在窗口外面if(RC0&RC)=0)/中点P和P0点跨越窗口时，P点和P1点肯定位于窗口之外，舍去PP1xx2=x,yy2=y;RC1=RC;else/中点在P0侧，舍去PP0点xx0=x,yy0=y;RC0=RC;x=(xx0+xx2)/2;y=(yy0+yy2)/2;RC=EnCode(x,y);/RC=0,中点在窗口内，以中点分为两段可以裁剪了MidClip(x,y,&xx0,&yy0,false);MidClip(x,y,&xx2,&yy2,true); accept=true;if(accept=true) drawLine(int(x0), int(y0), int(x2), int(y2)/绘制裁剪出的线段MidClip(float P0x, float P0y, float *P1x, float *P1y, bool flag)float x,y;/中点坐标int RCT0,RCT1,RCT;RCT0=EnCode(P0x,P0y);RCT1=EnCode(*P1x,*P1y);x=(P0x+*P1x)/2;y=(P0y+*P1y)/2;RCT=EnCode(x,y);while(fabs(x-P0x)1e-6|fabs(y-P0y)1e-6)if(RCT=0)/中点也在窗口内，则P=P0P0x=x;P0y=y;RCT0=RCT;else/否则舍弃P1点*P1x=x;*P1y=y;RCT1=RCT;x=(P0x+*P1x)/2;y=(P0y+*P1y)/2;RCT=EnCode(x,y);*P1x=x;*P1y=y;/*if(flag=true)xx2=x;yy2=y;elsexx0=x,yy0=y;*/ 梁友栋-Barsky算法ClipTest(float u, float v, float *tmax, float *tmin)/裁剪测试函数 /顺序左右下上float t;int ReturnValue=TRUE;if(u*tmin)ReturnValue=FALSE;else if(t*tmax)*tmax=t;elseif(u0.0)/内部到外部，计算终点处的tmint=v/u;if(t*tmax)ReturnValue=FALSE;else if(t*tmin)*tmin=t;else/平行于窗口边界的直线if(v0.0)/直线在窗口外可直接删除ReturnValue=FALSE;return(ReturnValue);BarskyClip(float x1, float y1, float x2, float y2)/裁剪函数float tmax,tmin,dx,dy;dx=x2-x1;dy=y2-y1;tmax=0.0,tmin=1.0;/窗口边界的左、右、下、上顺序裁剪直线if(ClipTest(-dx,x1-wxl,&tmax,&tmin)/n1,左边界u1x，v1x1wxlif(ClipTest(dx,wxr-x1,&tmax,&tmin)/n2，右边界u2x，v2wxrx1if(ClipTest(-dy,y1-wyb,&tmax,&tmin)/n3，下边界u3y，v3y1-wybif(ClipTest(dy,wyt-y1,&tmax,&tmin)/n4，上边界u4y，v4wyt-y1if(tmin0.0)/判断直线的起点x1+=tmax*dx;y1+=tmax*dy;drawLine(int(x0), int(y0), int(x2), int(y2)/绘制裁剪出的线段2、多边形的裁剪int ClipByEdgn(float *cinpointsx, float *cinpointsy, int cinnum, int inoutflag, int winedge) float sx,sy; int coutnum=0; /为裁剪后新多边形顶点数bool f; sx = cinpointsxcinnum-1; sy = cinpointsycinnum-1; /为裁剪前旧多边形最后一个顶点坐标 switch(inoutflag)case LEFT:if (sx = winedge) f = 0 ;/前一点在内 if (sx winedge) f = 1 ;/ 前一点在外 for(int i=0; i= winedge) /当前点在内 if (f = 1) /前一点在外 clippointsxcoutnum = winedge; /交点为新点, clippoints为输出点 clippointsycoutnum = sy + (cinpointsyi - sy) * (winedge - sx) / (cinpointsxi - sx); coutnum = coutnum + 1; f = 0; /当前点作为下一点的前一点（在内） clippointsxcoutnum = cinpointsxi; clippointsycoutnum = cinpointsyi; coutnum = coutnum + 1; /当前点为新点 else /当前点在外 if (f = 0) /前一点在内 clippointsxcoutnum = winedge; / 交点为新点 clippointsycoutnum = sy + (cinpointsyi - sy) * (winedge - sx) / (cinpointsxi - sx); coutnum = coutnum + 1; f = 1; sx = cinpointsxi; sy = cinpointsyi; break;case RIGHT:if (sx winedge) f = 1 ;/ 前一点在外 for(int i=0; icinnum; i+) if (cinpointsxi = winedge) f = 0 ;/前一点在内 if (sy winedge) f = 1 ;/ 前一点在外 for(int i=0; i= winedge) /当前点在内 if (f = 1) /前一点在外 clippointsycoutnum = winedge; /交点为新点 clippointsxcoutnum = sx + (cinpointsxi - sx) * (winedge - sy) / (cinpointsyi - sy); coutnum = coutnum + 1; f = 0; /当前点作为下一点的前一点（在内） clippointsxcoutnum = cinpointsxi; clippointsycoutnum = cinpointsyi; coutnum = coutnum + 1; /当前点为新点 else /当前点在外 if (f = 0) /前一点在内 clippointsycoutnum = winedge; / 交点为新点 clippointsxcoutnum = sx + (cinpointsxi - sx) * (winedge - sy) / (cinpointsyi - sy); coutnum = coutnum + 1; f = 1; sx = cinpointsxi; sy = cinpointsyi; break;case TOP:if (sy winedge) f = 1 ;/ 前一点在外 for(int i=0; icinnum; i+) if (cinpointsyi = winedge) /当前点在内 if (f = 1) /前一点在外 clippointsycoutnum = winedge; /交点为新点 clippointsxcoutnum = sx + (cinpointsxi - sx) * (winedge - sy) / (cinpointsyi - sy); coutnum = coutnum + 1; f = 0; /当前点作为下一点的前一点（在内） clippointsxcoutnum = cinpointsxi; clippointsycoutnum = cinpointsyi; coutnum = coutnum + 1;