请问怎样用Cohen-SutherLand算法做个矩形直线段裁剪的vc++程序

#include <Windows.h>

#include <gl/glut.h>

//////////////////////////////////////////////////////////////////////////

//区域码

const GLint leftBitCode=0x1

const GLint rightBitCode=0x2

const GLint buttonBitCode=0x4

const GLint topBitCode=0x8

GLint winWidth=640,winHeight=480

class screenPT

{

public:

GLfloat x,y

}

inline GLint inside(GLint code){return GLint(!code)} //判断点是否在裁剪区内

inline GLint reject(GLint code1,GLint code2){return GLint(code1&code2)}//判断能否完全排除一条线段

inline GLint accept(GLint code1,GLint code2){return GLint(!(code1 | code2))} //判断能否完全接受一条线段

inline void swapPT(screenPT&a,screenPT&b){screenPT t=aa=bb=t} //交换两个点

inline void swapCode(GLubyte&a,GLubyte&b){GLubyte t=aa=bb=t} //交换两个区域码

//确定一个点所在位置的区域码

GLubyte encode(const screenPT&p,const screenPT&winMin,const screenPT&winMax)

{

GLubyte code=0x00

if(p.x<winMin.x)

code |= leftBitCode

if(p.x>winMax.x)

code |= rightBitCode

if(p.y<winMin.y)

code |= buttonBitCode

if(p.y>winMax.y)

code |= topBitCode

return code

}

//在屏幕上画一条未裁剪的线，由裁剪函数调用

void drawOneLine(const screenPT&a,const screenPT&b)

{

glBegin(GL_LINES)

glVertex2f(a.x,a.y)

glVertex2f(b.x,b.y)

glEnd()

}

//裁剪函数

void lineClip(screenPT winMin,screenPT winMax,screenPT lineBegin,screenPT lineEnd)

{

GLubyte code1,code2 //保存两个端点的区域码

GLboolean done=false,plotLine=false //判断裁剪是否结束和是否要绘制直线

GLfloat k //斜率

while(!done)

{

code1 = encode(lineBegin,winMin,winMax)

code2 = encode(lineEnd,winMin,winMax)

if(accept(code1,code2)) //当前直线能完全绘制

{

done=true

plotLine=true

}

else

{

if(reject(code1,code2)) //当前直线能完全排除

done = true

else

{

if(inside(code1)) //若lineBegin端点在裁剪区内则交换两个端点使它在裁剪区外

{

swapPT(lineBegin,lineEnd)

swapCode(code1,code2)

}

//计算斜率

if(lineBegin.x != lineEnd.x)

k = (lineEnd.y-lineBegin.y)/(lineEnd.x-lineBegin.x)

//开始裁剪,以下与运算若结果为真，

//则lineBegin在边界外，此时将lineBegin移向直线与该边界的交点

if(code1 &leftBitCode)

{

lineBegin.y += (winMin.x-lineBegin.x)*k

lineBegin.x = winMin.x

}

else if(code1 &rightBitCode)

{

lineBegin.y += (winMax.x-lineBegin.x)*k

lineBegin.x = winMax.x

}

else if(code1 &buttonBitCode)

{

if(lineBegin.x != lineEnd.x)

lineBegin.x += (winMin.y-lineBegin.y)/k

lineBegin.y = winMin.y

}

else if(code1 &topBitCode)

{

if(lineBegin.x != lineEnd.x)

lineBegin.x += (winMax.y-lineBegin.y)/k

lineBegin.y = winMax.y

}

}

}

}

if(plotLine)

drawOneLine(lineBegin,lineEnd)//绘制裁剪好的直线

}

//////////////////////////////////////////////////////////////////////////

void rect(screenPT winMin,screenPT winMax)

{

glBegin(GL_LINE_LOOP)

glVertex2f(winMin.x,winMin.y)

glVertex2f(winMax.x,winMin.y)

glVertex2f(winMax.x,winMax.y)

glVertex2f(winMin.x,winMax.y)

glEnd()

}

void init()

{

glViewport(0,0,winWidth,winHeight)

glClearColor(1.0,1.0,1.0,0.0)

glMatrixMode(GL_PROJECTION)

glLoadIdentity()

gluOrtho2D(0,winWidth,0,winHeight)

glMatrixMode(GL_MODELVIEW)

}

void display()

{

screenPT winMin,winMax,lineBegin,lineEnd

winMin.x=100.0winMin.y=50.0

winMax.x=400.0winMax.y=300.0

lineBegin.x=0.0 lineBegin.y=0.0

lineEnd.x=winWidthlineEnd.y=winHeight

glClear(GL_COLOR_BUFFER_BIT)

glColor3f(0.0,0.0,0.0)

rect(winMin,winMax) //为裁剪区域绘制一个边框

lineClip(winMin,winMax,lineBegin,lineEnd)

lineBegin.y=240.0 lineEnd.y=240.0

lineClip(winMin,winMax,lineBegin,lineEnd)

lineBegin.x=320.0 lineBegin.y=0.0

lineEnd.x=320.0 lineEnd.y=winHeight

lineClip(winMin,winMax,lineBegin,lineEnd)

glFlush()

}

int main(int argc,char** argv)

{

glutInit(&argc,argv)

glutInitWindowPosition(100,100)

glutInitWindowSize(winWidth,winHeight)

glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB)

glutCreateWindow("my app")

init()

glutDisplayFunc(display)

glutMainLoop()

return 0

}

%[1]

x=0:8

y=(6-2)/(7-1)*(x-1)+2

plot(x,y,'o-')

grid

%[2]

t=0:0.1:2*pi,R=4

X=R*cos(t)+8

Y=R*sin(t)+8

plot(X,Y,'*-')

axis equal

grid

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