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# Flood Fill question

Posted on 1999-01-25
Medium Priority
671 Views
I obtained a flood fill algorithm from the net. It is a recursive function :

void floodFill(int x, int y, int fill, int old)
{
if ((x < 0) || (x >= raster.width)) return;
if ((y < 0) || (y >= raster.height)) return;
if (raster.getPixel(x, y) == old) {
raster.setPixel(fill, x, y);
floodFill(x+1, y, fill, old);
floodFill(x, y+1, fill, old);
floodFill(x-1, y, fill, old);
floodFill(x, y-1, fill, old);
}
}

i would like to apply this function into program where can flood fill a map with a tile. But i encounter 1 problem, that is when the map size is huge (say 1000x1000), since this is recursive function, it might call itself 1000x1000 times, and thus it blown out the stack and crashes the program.
How am i going to solve this problem ?
0
Question by:eugeneng
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LVL 3

Expert Comment

ID: 1328287
You either need to rewrite it into a nonrecursive loop or section
your map into smaller pieces and floodFill them individually.
0

LVL 1

Expert Comment

ID: 1328288
write your own stack using file & push all local variable when u call the function & pop on return.
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Accepted Solution

sunj earned 50 total points
ID: 1328289
Here is a non-recursive solution. Starting from a initial point(marked with FILLED), the function will enter a loop. For each loop, it scans through all the pixels in your map. Once it finds one pixel is marked with FILLED, it will try to mark some of its four neighbors as FILLED if they have the same color (just take care of the boundary). The loop terminates when there is no more change made to the map.

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LVL 1

Expert Comment

ID: 1328290
u can enlarge the size of each pixel by drawing rects instead of lighting pixels.
say 4x4 of 8x8 or something similar it will save you time .
or you can save the old coordinates and draw a big rect, and then restore what you had before , which will do the same trick even better.
both - ways you save time and effort , if you like more details please notify.
0

Author Comment

ID: 1328291
hi arbitrary, actually my map contains tiles instead of pixel, but basically they are the same. can you method still applicable to my program ? because i gotto check tile's data, not only color? if you method is still applicable, can you give me more detail of it.
0

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