Hello,

I’m starting on writing a simple paint application for OpenGL as part of my assignment. However, I am having problems with the Flood Fill algorithm needed to fill my polygons to a different color. I am using a seed of 4 recursive algorthm. 

My non-functioning code is:

void floodFill(Color oldColor, int x, int y){
	Color currentPixelColor = getPixelColor(x, y);

	if(equalColor(currentPixelColor, oldColor) == true){
			setFillColor(x, y);
			repaint();
			floodFill(oldColor, x + 1, y);
			floodFill(oldColor, x - 1, y);
			floodFill(oldColor, x, y + 1);
			floodFill(oldColor, x, y - 1);
		}
}

For my filling function (setFillColor(x, y)) is implemented by pushing back a point of the newColor, which is a global variable, into a vector. So everytime I call my repaint() function, the paint canvas will be redrawn with the newly pushed point in the vector.

The problem now is that whenever I run this function, I will be getting an infinite loop until the recursion is too deep. This happens to small polygons as well. I tried debugging by commenting out my lines so that the algorthm only fill pixels at the right of the seed, like this:

​
void floodFill(Color oldColor, int x, int y){
	Color currentPixelColor = getPixelColor(x, y);

	if(equalColor(currentPixelColor, oldColor) == true){
			setFillColor(x, y);
			repaint();
			floodFill(oldColor, x + 1, y);
			//floodFill(oldColor, x - 1, y);
			//floodFill(oldColor, x, y + 1);
			//floodFill(oldColor, x, y - 1);
		}
}
​

My output would be:

which works! It works for a single line recursive.

However, I encounter an infinite loop as soon as I uncomment a line and allow a 2 line-recursive algorithm. (left and right fill)

Could you help me take a look and enlighten me on what could be the problem?

Thank you so much, once again for your time