C Program to fill any given polygon using scan-line area filling algorithm

Editorial Team — Fri, 02 Oct 2009 10:34:38 +0000

#include 
#include 
#include 
#include 

struct Node
{
    int x;
    int y;
    struct Node* next;
};

void fill (int pt[][2], int clr);
void floodfill4 (int x, int y, int oldclr, int newclr);
void insert (int x, int y, struct Node** last);

void main()
{
    int i, j;
    int pt[3][2];
    int clr;

    printf ("This program demonstrates filling a polygon.\n");
    printf ("Enter the x- and y-coordinates for three points:\n");
    for (i=0; i<3; i++)
	for (j=0; j<2; j++)
	    scanf ("%d", &pt[i][j]);

    printf ("Enter the fill-colour: (Any number from 1 to 14) ");
    scanf ("%d", &clr);
    fill (pt, clr);
}

void fill (int pt[][2], int clr)
{
    int gd = DETECT, gm;
    int seedx, seedy;

    initgraph (&gd, &gm, "..\\bgi");

    setcolor (WHITE);
    line (pt[0][0], pt[0][1], pt[1][0], pt[1][1]);
    line (pt[1][0], pt[1][1], pt[2][0], pt[2][1]);
    line (pt[2][0], pt[2][1], pt[0][0], pt[0][1]);
    getch();

    seedx = (pt[0][0] + pt[1][0] + pt[2][0]) / 3;
    seedy = (pt[0][1] + pt[1][1] + pt[2][1]) / 3;

    floodfill4 (seedx, seedy, BLACK, clr);
    getch();

    closegraph();
    return;
}

void floodfill4 (int x, int y, int oldclr, int newclr)
{
    struct Node* first, *last, *tmp;

    first = (struct Node*) malloc (sizeof (struct Node));
    if (first == NULL)
    {
	closegraph();
	fprintf (stderr, "floodfill4: Out of memory.\n");
	exit (2);
    }
    if (oldclr == newclr)
    {
	free (first);
	return;
    }
   
    first->x = x;
    first->y = y;
    first->next = NULL;
    last = first;

    while (first != NULL)
    {
	putpixel (x, y, newclr);
	
	if (getpixel (x, y-1) == oldclr)
	{
	    putpixel (x, y-1, newclr);
	    insert (x, y-1, &last);
	}
	

	if (getpixel (x, y+1) == oldclr)
	{
	    putpixel (x, y+1, newclr);
	    insert (x, y+1, &last);
	}
	
	if (getpixel (x-1, y) == oldclr)
	{
	    putpixel (x-1, y, newclr);
	    insert (x-1, y, &last);
	}
	
	if (getpixel (x+1, y) == oldclr)
	{
	    putpixel (x+1, y, newclr);
	    insert (x+1, y, &last);
	}
	
	tmp = first;
	first = first->next;
	x = first->x;
	y = first->y;
	free (tmp);
    }
}

void insert (int x, int y, struct Node** last)
{
    struct Node* p;
    p = (struct Node*) malloc (sizeof (struct Node));
    if (p == NULL)
    {
	closegraph();
	fprintf (stderr, "\n insert: Out of memory.\n");
	exit (2);
    }
    
    p->x = x;
    p->y = y;
    p->next = NULL;
    (*last)->next = p;
    *last = (*last)->next;
}

The post C Program to fill any given polygon using scan-line area filling algorithm first appeared on Student Projects.

C Program to implement Bezier curves for a given set of control points.

Editorial Team — Fri, 02 Oct 2009 10:26:58 +0000

#include 
#include 
#include 
#include 

void bezier (int x[4], int y[4])
{
    int gd = DETECT, gm;
    int i;
    double t;

    initgraph (&gd, &gm, "..\\bgi");

    for (t = 0.0; t < 1.0; t += 0.0005)
    {
	double xt = pow (1-t, 3) * x[0] + 3 * t * pow (1-t, 2) * x[1] +
		    3 * pow (t, 2) * (1-t) * x[2] + pow (t, 3) * x[3];

	double yt = pow (1-t, 3) * y[0] + 3 * t * pow (1-t, 2) * y[1] +
		    3 * pow (t, 2) * (1-t) * y[2] + pow (t, 3) * y[3];

	putpixel (xt, yt, WHITE);
    }

    for (i=0; i<4; i++)
	putpixel (x[i], y[i], YELLOW);

    getch();
    closegraph();
    return;
}

void main()
{
    int x[4], y[4];
    int i;

    printf ("Enter the x- and y-coordinates of the four control points.\n");
    for (i=0; i<4; i++)
	scanf ("%d%d", &x[i], &y[i]);

    bezier (x, y);
}

The post C Program to implement Bezier curves for a given set of control points. first appeared on Student Projects.

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C Program to fill any given polygon using scan-line area filling algorithm

C Program to implement Bezier curves for a given set of control points.