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# Program of scanfill algorithm

Posted By: Easy Tutor     Category: C++ Programming     Views: 4460

## Code for Program of scanfill algorithm in C++ Programming

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

struct Polygon
{
int x;
int y;
};

struct edRecord
{
int YUpper;
float XIntersect;
float dxperscan;
struct edRecord *Next;
};

typedef struct edRecord Edge;
typedef struct Polygon Nodes;
Edge  *Active;
Edge **Edges;
int Cntr=6;
Nodes NodesObj[6]={{100,100},{150,150},{150,200},{100,250},{50,200},{50,150}};

void Scanfill();
void InsertEdge(Edge*,Edge*);
void BuildEdgeList(int,Nodes*);
int YNext(int);
void MakeEdgeRec(Nodes,Nodes,int,Edge*);
void BulidActiveList(int);
void UpdateActiveList(int);
void DeleteAfter(Edge*);
void ResortActiveList(void);
void ResortActiveList(int);

//**************************************************************************void main()
{
int gDriver = DETECT, gMode;
int n,xArray[12];
int iCntr,jCntr;

initgraph(&gDriver,&gMode,"c:\\tc\\bgi");

for(iCntr=0,jCntr=0;iCntr<12;iCntr+=2,jCntr++)
xArray[iCntr] = NodesObj[jCntr].x;
for(iCntr=1,jCntr=0;iCntr<12;iCntr+=2,jCntr++)
xArray[iCntr] = NodesObj[jCntr].y;

drawpoly(6,xArray);

line(NodesObj[5].x,NodesObj[5].y,NodesObj[0].x,NodesObj[0].y);   //TO CLOSE POLYGON
getch();

Scanfill();
getch();
closegraph();
restorecrtmode();
return;
}

//**************************************************************************void Scanfill()
{
int iCntr,Scan;
//initialize edgelists with dummy nodes
Edges=new Edge*[getmaxy()];
for(iCntr=0;iCntr<getmaxy();iCntr++)
{
Edges[iCntr] = new Edge;
Edges[iCntr]->Next = NULL;
}
//initialize Active edgeList with dummy nodes
Active = new Edge;
Active->Next = NULL;
BuildEdgeList(Cntr,NodesObj);
for(Scan=0;Scan<getmaxy();Scan++)
{
BulidActiveList(Scan);
if (Active->Next != NULL)
{
ResortActiveList(Scan);
UpdateActiveList(Scan);
ResortActiveList();
}
}
}

//**************************************************************************void InsertEdge(Edge* edgeList,Edge* InitialEdge)
{
Edge *PEdge,*QEdges;

QEdges=edgeList;
PEdge=QEdges->Next;
while(PEdge!=NULL)
if(InitialEdge->XIntersect < PEdge->XIntersect)
PEdge=NULL;
else
{
QEdges=PEdge;
PEdge=PEdge->Next;
}
InitialEdge->Next = QEdges->Next;
QEdges->Next = InitialEdge;
}

//**************************************************************************void BuildEdgeList(int Cntr,Nodes* Vertices)
{
Edge* NewEdge;
Nodes Vertex1,Vertex2;
int YPrev,iCntr;
Vertex1.x=Vertices[Cntr-1].x;
Vertex1.y=Vertices[Cntr-1].y;
YPrev = Vertices[Cntr-2].y;
for(iCntr=0;iCntr<Cntr;iCntr++)
{
Vertex2.x = Vertices[iCntr].x;
Vertex2.y = Vertices[iCntr].y;
if(Vertex1.y != Vertex2.y)
{
NewEdge = new Edge;
if(Vertex1.y < Vertex2.y)
MakeEdgeRec(Vertex1,Vertex2,YNext(iCntr),NewEdge);
else
MakeEdgeRec(Vertex2,Vertex1,YPrev,NewEdge);
}
YPrev = Vertex1.y;
Vertex1.x = Vertex2.x;
Vertex1.y = Vertex2.y;
}
}

//**************************************************************************void BulidActiveList(int Scan)
{
Edge *PEdge,*QEdges;
PEdge=Edges[Scan]->Next;
while(PEdge!=NULL)
{
QEdges=PEdge->Next;
InsertEdge(Active,PEdge);
PEdge=QEdges;
}
}

//***************************************************************************void ResortActiveList(int Scan)
{
Edge *iEdge,*jEdge;
int iCntr;
iEdge = Active->Next;
while(iEdge!=NULL)
{
jEdge = iEdge->Next;
for(iCntr=iEdge->XIntersect;iCntr<=jEdge->XIntersect-1;iCntr++)
putpixel(iCntr,Scan,RED);
iEdge=jEdge->Next;
}
}
//***************************************************************************void UpdateActiveList(int Scan)
{
Edge *PEdge,*QEdges;
QEdges=Active;
PEdge=Active->Next;
while(PEdge!=NULL)
{
if(Scan>=PEdge->YUpper)
{
PEdge=PEdge->Next;
DeleteAfter(QEdges);
}
else
{
PEdge->XIntersect+=PEdge->dxperscan;
QEdges=PEdge;
PEdge=PEdge->Next;
}
}
}
//***************************************************************************void ResortActiveList()
{
Edge *PEdge,*QEdges;
PEdge=Active->Next;
Active->Next=NULL;
while(PEdge!=NULL)
{
QEdges=PEdge->Next;
InsertEdge(Active,PEdge);
PEdge=QEdges;
}
}

//***************************************************************************int YNext(int YCurr)
{
int jCntr;
if(YCurr+1>Cntr)
jCntr=1;
else
jCntr=YCurr+1;
while(NodesObj[YCurr].y == NodesObj[jCntr].y)
{
if(jCntr+1>Cntr)
jCntr=1;
else
jCntr++;
}
return(NodesObj[jCntr].y);
}

//***************************************************************************void DeleteAfter(Edge* QEdges)
{
Edge* PEdge;

PEdge = QEdges->Next;
QEdges->Next = PEdge->Next;
delete PEdge;
}

//***************************************************************************void MakeEdgeRec(Nodes Lower,Nodes Upper,int YComp,Edge* CurrEdge)
{
CurrEdge->dxperscan = (Upper.x - Lower.x) / (Upper.y - Lower.y);
CurrEdge->XIntersect = Lower.x;
if(Upper.y < YComp)
CurrEdge->YUpper = Upper.y - 1;
else
CurrEdge->YUpper = Upper.y;
InsertEdge(Edges[Lower.y],CurrEdge);
}
```
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