Please help convering recursion to iteration

Question

Hello all, I am relatively new with Java. I am implementing a Region Growing algorithm, and it works fine for small regions. For large regions, I get the usual stack overflow problem. I was never able to increase my stack size and didn't really want that approach. I have posted the method that does the region growing. It is messy, and I know there is stuff in there that will not make sense but, the region growing section is there. I have given up and need some help...
Thanks everyone who can help!!
     private void growRegion(int x, int y) {
          double red = 0;
          double green = 0;
          double blue = 0;
          double alpha = 0;
          pixelArray2 = new double[5];
          wraster.getPixel(x,y,pixelArray2);
          red      = pixelArray2[0];
          green      = pixelArray2[1];
          blue      = pixelArray2[2];
          alpha      = pixelArray2[3];
          pixelChange2[0] = 195;
          pixelChange2[1] = 195;
          pixelChange2[2] = 195;
          pixelChange2[3] = alpha;
          if (x < 0 || y < 0) return;     
          if (x >= wraster.getWidth()) return;     
          if (y >= wraster.getHeight()) return;     
// the pixel has been assigned a threshold but has not been associated
// with a region.
          if (assigned[x][y]==true && associated[x][y]==false){     
               wraster.setPixel(x,y,pixelChange2);
associated[x][y] = true;          
// the recursive calls that are driving me nuts
               growRegion(x+1,y);                    
               growRegion(x-1,y);          
               growRegion(x,y+1);          
               growRegion(x,y-1);
          }else{
// do something else...anything but recursion
     }

Answer 1

You should use some recursion but this looks like an over-use. Method growRegion starts (after some initializations) with a termination statement,
if (x < 0 || y < 0) return;
if (x >= wraster.getWidth()) return;
if (y >= wraster.getHeight()) return; This means you could probably remove this and instead use for-loops to drive the recursion,
if (d != 0)
   for (int i=x+1, l=wraster.getWidth(); i<l; i++)
      growRegion(i,y,0);
if (d != 1)
   for (int i=x-1; i>=0; i--)
      growRegion(i,y,1);
if (d != 2)
   for (int i=y+1, l=wraster.getHeight(); i<l; i++)
      growRegion(x,i,2);
if (d != 3)
   for (int i=y-1; i>=0; i--)
      growRegion(x,i,3); The signature of growRegion is now,
growRegion(int x, int y, int d)And in the very first call d (direction) must be -1. I think this will replace lots of (unnecessary) recursion with iteration but I'm not sure. It an easy change so it could be worth a try -:)