Flood Fill Algorithm

Flood Fill Algorithm is a computer graphics algorithm used to fill a bounded area with a specified color. It works by starting from a seed point inside the area and then flooding outwards to fill the entire area with the fill color.

The basic steps of the flood fill algorithm are:

1. Choose a seed point inside the area to be filled.

2. Set the color of the seed point to the desired fill color.

3. Check the color of the neighboring pixels of the seed point. If their color is not the boundary color and not the fill color, then set their color to the fill color and add them to a list of pixels to be checked.

4. Repeat step 3 for each pixel in the list until all adjacent pixels have been checked.

5. Remove each pixel from the list as it is checked to avoid processing it multiple times.

6. Repeat step 4 and 5 until the entire area is filled.

The flood fill algorithm is similar to the boundary fill algorithm, but it does not require a boundary point to start from. It can be used to fill irregularly shaped areas, such as the inside of a closed curve or a freehand drawing.

However, the basic flood fill algorithm may not work as expected when there are holes or gaps inside the area. To handle such cases, we can use the flood fill algorithm with the boundary condition to detect and fill the holes.

One issue with the flood fill algorithm is that it can go into an infinite loop if it encounters a pixel that has already been filled. To prevent this, we can add a boundary condition to check if the current pixel has already been filled before adding it to the list of pixels to be checked.

Overall, the flood fill algorithm is simple and easy to implement, but it can be slow for large areas or complex shapes. To optimize the algorithm, we can use a non-recursive approach such as the scan-line algorithm or the queue-based approach.