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Uploaded byMani Kanth
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Seed filling algorithm

The document discusses two algorithms for filling polygons: boundary fill and flood fill. Boundary fill starts at a point inside the polygon and fills pixels until it reaches the boundary color. Flood fill replaces all pixels of a specified interior color with a fill color. Both can be implemented with 4-connected or 8-connected pixels. Flood fill colors the entire area but uses more memory, while boundary fill stops at the boundary and is more efficient.

Engineering◦
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For highlighting all the pixels inside the polygon, 2 approaches can be used- 1. Scan Fill 2. Seed Fill (Boundary Fill, Flood Fill )
Boundary Fill Algorithm This algorithm picks a point inside the polygon and starts to fill until it hits the boundary of the object. Assumption: In this algorithm, we assume that color of the boundary is same for the entire object.
void boundaryfill(int x,int y,int fill_color,int boundary_color) { if(getpixel(x,y)!=boundary_color && getpixel(x,y)!=fill_color) { putpixel(x,y,fill_color); boundaryfill(x+1,y,fill_color,boundary_color); boundaryfill(x-1,y, fill_color,boundary_color); boundaryfill(x,y+1, fill_color,boundary_color); boundaryfill(x,y-1, fill_color,boundary_color); } }
Sometimes we want to fill in an area that is not defined within a single color boundary. We 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.
void floodfill(int x,int y,int fill_color,int old_color) { if(getpixel(x,y)==old_color) { putpixel(x,y,fill_color); floodfill(x+1,y,fill_color,old_color); floodfill(x-1,y, fill_color,old_color); floodfill(x,y+1, fill_color,old_color); floodfill(x,y-1, fill_color,old_color); } }
In brief: Flood Fill and Boundary Fill are algorithms used for coloring a given figure with a chosen color Flood Fill is one in which all connected pixels of a selected color get replaced by a fill color.  Boundary Fill is very similar with the difference being the program stopping when a given color boundary is found.
Boundary Fill Algorithm /Flood Fill algorithm The boundary fill algorithm/ flood fill algorithm can be implemented by 4-connected pixels or 8-connected pixels. 4-connected 8-connected
Start Position 4-connected (Example)
3 2 1 1 2 3
1 4 2 4 2 1
1 2 2 1
5 1 5 1
1 1
Some region remains unfilled
Start Position 8-connected (Example)
4 1 5 2 3 5 4 3 2 1
6 4 1 2 3 6 4 3 2 1
7 8 4 1 2 3 8 7 4 3 2 1
11 9 12 7 10 4 1 2 3 12 11 10 9 7 4 3 2 1
11 9 7 10 4 1 2 3 11 10 9 7 4 3 2 1
9 7 10 4 1 2 3 10 9 7 4 3 2 1
9 7 4 1 2 3 9 7 4 3 2 1
7 4 1 2 3 7 4 3 2 1
4 1 2 3 4 3 2 1
1 2 3 3 2 1
1 2 2 1
1 1
Comparison Flood Fill Algorithm  Flood fill colors an entire area in an enclosed figure through interconnected pixels using a single color  So, Flood Fill is one in which all connected pixels of a selected color get replaced by a fill color.  A flood fill may use an unpredictable amount of memory to finish because it isn't known how many sub-fills will be spawned  Time Consuming Boundary Fill Algorithm  Here area gets colored with pixels of a chosen color as boundary this giving the technique its name  Boundary Fill is very similar with the difference being the program stopping when a given color boundary is found.  Boundary fill is usually more complicated but it is a linear algorithm and doesn't require recursion  It is less Time Consuming
Seed filling algorithm