Flood-Fill Algorithm

Flood-Fill Algorithm

Sometimes we want to fill in (or recolor) an area that is not defined within a single

color boundary. Figure 3-46 shows an area bordered by several different color

regions. We can paint such areas by replacing a specified interior color instead of

searching for a boundary color value. This approach is called a flood-fill algorithm.

We start from a specified interior point (x, y) and reassign all pixel values

that are currently set to a given interior color with the desired fill color. If the area

we want to paint has more than one interior color, we can first reassign pixel values

so that all interior points have the same color. Using either a Cconnected or

8-connected approach, we then step through pixel positions until all interior

points have been repainted. The following procedure flood fills a konnected region

recursively, starting from the input position.

voiQfloodFill4 ( i n t x, i n t y, i n t f i l l c o l o r , i n t oldcolor)

f

i f (getpixel (x. y) == oldcolor) (

setcolor ( f i l l c o l o r ) ;

setpixel (x, y ) :

floodFill4 ( x + l , y, fillColor, oldColor):

floodfill4 (x-1, y, fillcolor, oldcolor);

floodPill4 (x, y + l , fillcolor, oldcolor);

floodFill4 ( x , y-1, fillColor, oldcolor);