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# Program to show the implementation of Sutherland-Hodgeman Polygon Clipping Algorithm

Posted By: Easy Tutor     Category: C++ Programming     Views: 8614

## Code for Program to show the implementation of Sutherland-Hodgeman Polygon Clipping Algorithm in C++ Programming

``` # include <iostream.h>
# include <graphics.h>
# include    <conio.h>
# include     <math.h>

class PointCoordinates
{
public:
float x;
float y;

PointCoordinates( )
{
x=0;
y=0;
}
};

/*************************************************************************///---------------------------  LineCoordinates  -------------------------///*************************************************************************/class LineCoordinates
{
public:
float x_1;
float y_1;
float x_2;
float y_2;

LineCoordinates( )
{
x_1=0;
y_1=0;
x_2=0;
y_2=0;
}

LineCoordinates(constfloat x1,constfloat y1,
constfloat x2,constfloat y2)
{
x_1=x1;
y_1=y1;
x_2=x2;
y_2=y2;
}
};

/*************************************************************************///-------------------------  WindowCoordinates  -------------------------///*************************************************************************/class WindowCoordinates
{
public:
float x_min;
float y_min;
float x_max;
float y_max;

WindowCoordinates(constfloat x1,constfloat y1,
constfloat x2,constfloat y2)
{
x_min=x1;
y_min=y1;
x_max=x2;
y_max=y2;
}
};

void show_screen( );

void clip_polygon(const WindowCoordinates,constint,constint []);

constint check_line(const LineCoordinates,const LineCoordinates);
constint check_point(const LineCoordinates,constfloat,constfloat);

const PointCoordinates get_intersection_point(LineCoordinates,
LineCoordinates);

void Polygon(constint,constint []);
void Rectangle(constint,constint,constint,constint);
void Line(constint,constint,constint,constint);

int main( )
{
int driver=VGA;
int mode=VGAHI;

initgraph(&driver,&mode,"..\\Bgi");

show_screen( );

WindowCoordinates WC(180,140,470,340);

setcolor(15);
Rectangle(WC.x_min,WC.y_min,WC.x_max,WC.y_max);

int n=10;

int polygon_vertices[20]={ 100,240 , 180,370 , 210,310 , 380,375 ,
520,310 , 480,260 , 510,80  , 280,180 ,
210,90  , 100,240 };

setcolor(7);
Polygon(n,polygon_vertices);

setcolor(15);
settextstyle(0,0,1);
outtextxy(300,240,"Window");
outtextxy(80,240,"Polygon");

char Key=NULL;

do
{
Key=getch( );
}
while(Key!='C' && Key!='c');

settextstyle(0,0,1);
setcolor(0);
outtextxy(163,450,"  Press 'C' to see the Clipped Polygon. ");

setcolor(15);
outtextxy(163,450,"------                          ---------");

setcolor(12);
outtextxy(213,450,"  Press any Key to exit.  ");

clip_polygon(WC,n,polygon_vertices);

setcolor(15);
settextstyle(0,0,1);
outtextxy(280,155,"Clipped Polygon");

getch( );
return 0;
}

/*************************************************************************///--------------------------  clip_polygon( )  --------------------------///*************************************************************************/void clip_polygon(const WindowCoordinates wc,constint n,
constint polygon_edges[])
{
int edges_counter;
int number_of_edges=n;

int *edges=newint[(n*4)];
int *clipped_edges=newint[(n*4)];

for(int count_1=0;count_1<(n*2);count_1++)
edges[count_1]=polygon_edges[count_1];

LineCoordinates window_line;

for(int count_2=1;count_2<=4;count_2++)
{
edges_counter=1;

for(int count_3=0;count_3<(number_of_edges*4);count_3++)
clipped_edges[count_3]=0;

if(count_2==1)
{
window_line.x_1=wc.x_min;
window_line.y_1=wc.y_max;
window_line.x_2=wc.x_max;
window_line.y_2=wc.y_max;
}

elseif(count_2==2)
{
window_line.x_1=wc.x_max;
window_line.y_1=wc.y_max;
window_line.x_2=wc.x_max;
window_line.y_2=wc.y_min;
}

elseif(count_2==3)
{
window_line.x_1=wc.x_max;
window_line.y_1=wc.y_min;
window_line.x_2=wc.x_min;
window_line.y_2=wc.y_min;
}

elseif(count_2==4)
{
window_line.x_1=wc.x_min;
window_line.y_1=wc.y_min;
window_line.x_2=wc.x_min;
window_line.y_2=wc.y_max;
}

int rule_no;

PointCoordinates point;

for(int count_4=1;count_4<number_of_edges;count_4++)
{
LineCoordinates line(edges[((count_4*2)-2)],
edges[((count_4*2)-1)],
edges[(count_4*2)],
edges[((count_4*2)+1)]);

rule_no=check_line(window_line,line);

switch(rule_no)
{
case 1 : clipped_edges[(edges_counter*2)]=
(int)(line.x_2+0.5);
clipped_edges[((edges_counter*2)+1)]=
(int)(line.y_2+0.5);
edges_counter++;
break;

case 2 : break;

case 3 : point=
get_intersection_point(window_line,line);

clipped_edges[(edges_counter*2)]=
(int)(point.x+0.5);
clipped_edges[((edges_counter*2)+1)]=
(int)(point.y+0.5);
edges_counter++;
break;

case 4 : point=
get_intersection_point(window_line,line);

clipped_edges[(edges_counter*2)]=
(int)(point.x+0.5);
clipped_edges[((edges_counter*2)+1)]=
(int)(point.y+0.5);
edges_counter++;

clipped_edges[(edges_counter*2)]=
(int)(line.x_2+0.5);
clipped_edges[((edges_counter*2)+1)]=
(int)(line.y_2+0.5);
edges_counter++;
break;
}
}

clipped_edges[0]=clipped_edges[((edges_counter*2)-2)];
clipped_edges[1]=clipped_edges[((edges_counter*2)-1)];

for(int count_5=0;count_5<(edges_counter*2);count_5++)
edges[count_5]=0;

number_of_edges=edges_counter;

for(int count_6=0;count_6<(edges_counter*2);count_6++)
edges[count_6]=clipped_edges[count_6];
}

setcolor(10);
Polygon(number_of_edges,edges);

delete edges;
delete clipped_edges;
}

/*************************************************************************///----------------------------  check_line( )  --------------------------///*************************************************************************/constint check_line(const LineCoordinates line,const LineCoordinates edge)
{
int rule_number=0;
int point_1=check_point(line,edge.x_1,edge.y_1);
int point_2=check_point(line,edge.x_2,edge.y_2);

if(point_1==1 && point_2==1)
rule_number=1;

elseif(point_1!=1 && point_2!=1)
rule_number=2;

elseif(point_1==1 && point_2!=1)
rule_number=3;

elseif(point_1!=1 && point_2==1)
rule_number=4;

return rule_number;
}

/*************************************************************************///----------------------------  check_point( )  -------------------------///*************************************************************************/constint check_point(const LineCoordinates lc,constfloat x,constfloat y)
{
float c=(((lc.x_2-lc.x_1)*(y-lc.y_1))-((lc.y_2-lc.y_1)*(x-lc.x_1)));

if(c<=0)
return 1;

elsereturn 0;
}

/*************************************************************************///----------------------  get_intersection_point( )  --------------------///*************************************************************************/const PointCoordinates get_intersection_point(LineCoordinates lc1,
LineCoordinates lc2)
{
float x_min=lc1.x_1;
float x_max=lc1.x_2;
float y_min=lc1.y_1;
float y_max=lc1.y_2;

if(lc1.x_1==lc1.x_2)
{
if(lc2.y_2>=lc2.y_1 && lc2.y_2>y_max)
y_max=lc2.y_2;

elseif(lc2.y_1>lc2.y_2 && lc2.y_1>y_max)
y_max=lc2.y_1;

if(lc2.y_1<=lc2.y_2 && lc2.y_1<y_min)
y_min=lc2.y_1;

elseif(lc2.y_2<lc2.y_1 && lc2.y_2<y_min)
y_min=lc2.y_2;
}

elseif(lc1.y_1==lc1.y_2)
{
if(lc2.x_2>=lc2.x_1 && lc2.x_2>x_max)
x_max=lc2.x_2;

elseif(lc2.x_2<lc2.x_1 && lc2.x_1>x_max)
x_max=lc2.x_1;

if(lc2.x_1<=lc2.x_2 && lc2.x_1<x_min)
x_min=lc2.x_1;

elseif(lc2.x_2<lc2.x_1 && lc2.x_2<x_min)
x_min=lc2.x_2;
}

float x_mid;
float y_mid;

if(lc2.y_1>y_max)
{
while(lc2.y_1!=y_max)
{
x_mid=((lc2.x_1+lc2.x_2)/2);
y_mid=((lc2.y_1+lc2.y_2)/2);

if(y_mid>=y_max)
{
lc2.x_1=x_mid;
lc2.y_1=y_mid;
}

else
{
lc2.x_2=x_mid;
lc2.y_2=y_mid;
}
}
}

elseif(lc2.y_1<y_min)
{
while(lc2.y_1!=y_min)
{
x_mid=((lc2.x_1+lc2.x_2)/2);
y_mid=((lc2.y_1+lc2.y_2)/2);

if(y_mid<=y_min)
{
lc2.x_1=x_mid;
lc2.y_1=y_mid;
}

else
{
lc2.x_2=x_mid;
lc2.y_2=y_mid;
}
}
}

if(lc2.x_1>x_max)
{
while(lc2.x_1!=x_max)
{
x_mid=((lc2.x_1+lc2.x_2)/2);
y_mid=((lc2.y_1+lc2.y_2)/2);

if(x_mid>=x_max)
{
lc2.x_1=x_mid;
lc2.y_1=y_mid;
}

else
{
lc2.x_2=x_mid;
lc2.y_2=y_mid;
}
}
}

elseif(lc2.x_1<x_min)
{
while(lc2.x_1!=x_min)
{
x_mid=((lc2.x_1+lc2.x_2)/2);
y_mid=((lc2.y_1+lc2.y_2)/2);

if(x_mid<=x_min)
{
lc2.x_1=x_mid;
lc2.y_1=y_mid;
}

else
{
lc2.x_2=x_mid;
lc2.y_2=y_mid;
}
}
}

PointCoordinates ipt;

ipt.x=lc2.x_1;
ipt.y=lc2.y_1;

return ipt;
}

/*************************************************************************///---------------------------  Rectangle( )  ----------------------------///*************************************************************************/void Rectangle(constint x_1,constint y_1,constint x_2,constint y_2)
{
Line(x_1,y_1,x_2,y_1);
Line(x_2,y_1,x_2,y_2);
Line(x_2,y_2,x_1,y_2);
Line(x_1,y_2,x_1,y_1);
}

/*************************************************************************///-----------------------------  Polygon( )  ----------------------------///*************************************************************************/void Polygon(constint n,constint coordinates[])
{
if(n>=2)
{
Line(coordinates[0],coordinates[1],
coordinates[2],coordinates[3]);

for(int count=1;count<(n-1);count++)
Line(coordinates[(count*2)],coordinates[((count*2)+1)],
coordinates[((count+1)*2)],
coordinates[(((count+1)*2)+1)]);
}
}

/*************************************************************************///--------------------------  Line( )  ------------------------///*************************************************************************/void Line(constint x_1,constint y_1,constint x_2,constint y_2)
{
int color=getcolor( );

int x1=x_1;
int y1=y_1;

int x2=x_2;
int y2=y_2;

if(x_1>x_2)
{
x1=x_2;
y1=y_2;

x2=x_1;
y2=y_1;
}

int dx=abs(x2-x1);
int dy=abs(y2-y1);
int inc_dec=((y2>=y1)?1:-1);

if(dx>dy)
{
int two_dy=(2*dy);
int two_dy_dx=(2*(dy-dx));
int p=((2*dy)-dx);

int x=x1;
int y=y1;

putpixel(x,y,color);

while(x<x2)
{
x++;

if(p<0)
p+=two_dy;

else
{
y+=inc_dec;
p+=two_dy_dx;
}

putpixel(x,y,color);
}
}

else
{
int two_dx=(2*dx);
int two_dx_dy=(2*(dx-dy));
int p=((2*dx)-dy);

int x=x1;
int y=y1;

putpixel(x,y,color);

while(y!=y2)
{
y+=inc_dec;

if(p<0)
p+=two_dx;

else
{
x++;
p+=two_dx_dy;
}

putpixel(x,y,color);
}
}
}

/*************************************************************************///--------------------------  show_screen( )  ---------------------------///*************************************************************************/void show_screen( )
{
setfillstyle(1,1);
bar(125,26,510,38);

settextstyle(0,0,1);
setcolor(15);
outtextxy(5,5,"******************************************************************************");
outtextxy(5,17,"*-**************************************************************************-*");
outtextxy(5,29,"*-------------                                                  -------------*");
outtextxy(5,41,"*-**************************************************************************-*");
outtextxy(5,53,"*-**************************************************************************-*");

setcolor(11);
outtextxy(134,29,"Sutherland-Hodgeman Polygon Clipping Algorithm");

setcolor(15);

for(int count=0;count<=30;count++)
outtextxy(5,(65+(count*12)),"*-*                                                                        *-*");

outtextxy(5,438,"*-**************************************************************************-*");
outtextxy(5,450,"*-------------------                                         ----------------*");
outtextxy(5,462,"******************************************************************************");

setcolor(12);
outtextxy(163,450,"  Press 'C' to see the Clipped Polygon. ");
}
```
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