Efficient Boundary Fill

Seed Value x, y:

1. scanRight( y, x )

2. scanLeft( y, x – 1 )

ScanUp:

1. if y > 0 {

2. scan (y, x1, x2, ups)

3. if ( L blank) scanLeft ( y, x1 – 1 )

4. if ( R blank) scanRight ( y, x2 + 1 )

5. }

ScanDown:

1. if y <= maxy {

2. scan (y, x1, x2, downs)

3. if ( L blank) scanLeft ( y, x1 – 1 )

4. if ( R blank) scanRight ( y, x2 + 1 )

5. }

scan:

Finds spans and pushes them on stack to scanUp or ScanDown as requested, leaving pixel x1 in L and pixel x2 in R

scanLeft:

Pushes only one interval, if there is one, to scanUp & scanDown

scanRight:

Pushes only one interval, if there is one, to scanUp & scanDown