# Fillflood algo and SDL

I send you a not recursive sdl function , I have found

http://www.acm.org/tog/GraphicsGems/ ( thank’s frank for this link :).

It’s seem to work , and don’t make any core dump.

void setPixels(SDL_Surface *s,int x,int y,Uint32 c);
Uint32 getPixels(SDL_Surface s,int x,int y);
/

• A Seed Fill Algorithm
• by Paul Heckbert
• from “Graphics Gems”, Academic Press, 1990*
• user provides pixelread() and pixelwrite() routines
*/
typedef struct {short y, xl, xr, dy;} Segment;

/*

• Filled horizontal segment of scanline y for xl<=x<=xr.
• Parent segment was on line y-dy. dy=1 or -1
*/

#define MAX 10000 /* max depth of stack */

#define PUSH(Y, XL, XR, DY,S) /* push new segment on stack */
if (sp<stack+MAX && Y+(DY)>=0 && Y+(DY)<=S->h)
{sp->y = Y; sp->xl = XL; sp->xr = XR; sp->dy = DY; sp++;}

#define POP(Y, XL, XR, DY) /* pop segment off stack */
{sp–; Y = sp->y+(DY = sp->dy); XL = sp->xl; XR = sp->xr;}

/*

• fill: set the pixel at (x,y) and all of its 4-connected neighbors

• with the same pixel value to the new pixel value nv.

• A 4-connected neighbor is a pixel above, below, left, or right of a
pixel.
/
/
*****************************/
void floodfill(SDL_Surface *win,int x,int y, Uint32 nv)
{
int l, x1, x2, dy;
Segment stack[MAX], sp = stack; / stack of filled segments */
Uint32 ov=getPixels(win,x,y);

if (x<0 || y<0 || x>=win->w || y>=win->h ) return;
if (ov==nv) return;
PUSH(y, x, x, 1,win); /* needed in some cases
/
PUSH(y+1, x, x, -1,win); /
seed segment (popped 1st) */

while (sp>stack) {
/* pop segment off stack and fill a neighboring scan line /
POP(y, x1, x2, dy);
/

* segment of scan line y-dy for x1<=x<=x2 was previously
filled,
* now explore adjacent pixels in scan line y
/
for (x=x1; x>=0 && getPixels(win,x, y)==ov; x–)
setPixels(win,x,y,nv);
if (x>=x1) goto skip;
l = x+1;
if (l<x1) PUSH(y, l, x1-1, -dy,win); /
leak on left?
/
x = x1+1;
do {
for (; x<=win->w && getPixels(win,x, y)==ov; x++)
setPixels(win,x, y, nv);
PUSH(y, l, x-1, dy,win);
if (x>x2+1) PUSH(y, x2+1, x-1, -dy,win); /
leak on
right? */
skip: for (x++; x<=x2 && getPixels(win,x, y)!=ov; x++);
l = x;
} while (x<=x2);
}
}

charles.