计算机图形学实验报告 直线段的裁剪

直线段的裁剪

CaaaaView::CaaaaView()

{

m_pntCount=0;

xl=200;

xr=600;

yb=100;

yt=350;

}

void MidBresenhamLine(CDC *pDC,int x0,int y0,int x1,int y1){ int dx,dy,d,up,down,x,y;

if(x0>x1){

x=x1;x1=x0;x0=x;

y=y1;y1=y0;y0=y;

}

x=x0;y=y0;

dx=x1-x0;dy=y1-y0;

d=dx-2*dy;

up=2*x-2*y;down=-2*dy;

while(x<=x1){

pDC->SetPixel(x,y,355);

x++;

if(d<0){

y++;

d+=up;

}

else d+=down;

}

}

int LBLineClipTest(float p,float q,float &umax,float &umin) {

float r=0.0;

if(p<0.0){

r=q/p;

TRACE(_T("r=%.4f\n"),r);

if(r>umin) return 0;

else if(r>umax) umax=r;

}

else if(p>0.0){

r=q/p;

TRACE(_T("r=%.4f\n"),r);

if(r

else if(r

}

else if(q<0.0) return 0;

return 1;

}

void LBLineClip(CDC* pDC,float xl,float xr,float yb,float yt,float x1,float y1,float x2,float y2)

{

float umax,umin,deltax,deltay;

deltax=x2-x1; deltay=y2-y1; umax=0.0; umin=1.0;

if( LBLineClipTest(-deltax,x1-xl,umax,umin)){

if( LBLineClipTest(deltax,xr-x1,umax,umin)){

if( LBLineClipTest(-deltay,y1-yb,umax,umin)){

if( LBLineClipTest(deltay,yt-y1,umax,umin)){

x1=int(x1+umax*deltax+0.5);

y1=int(y1+umax*deltay+0.5);

x2=int(x1+umin*deltax+0.5);

y2=int(y1+umin*deltay+0.5);

}

MidBresenhamLine(pDC,x1,y1,x2,y2);

}

}

}

}

void CaaaaView::OnLButtonDown(UINT nFlags, CPoint point)

{

//AfxMessageBox(_T("click"));

m_pnts[m_pntCount]=point;

m_pntCount++;

if(m_pntCount>1)

{

CDC *pDC=GetDC();

LBLineClip(pDC,xl,xr,yb,yt,m_pnts[m_pntCount-2].x,m_pnts[m_pntCount-2].y,m_pnts[m_pntCo unt-1].x,m_pnts[m_pntCount-1].y);

ReleaseDC(pDC);

m_pntCount=0;

}

CView::OnLButtonDown(nFlags, point);

}