-- demo\rosetta\Bitmap_FloodFill.exw  (runnable version)
include ppm.e -- blue, green, read_ppm(), write_ppm() (covers above requirements)

function ff(sequence img, integer x, y, colour, target)
    if  x>=1 and x<=length(img)
    and y>=1 and y<=length(img[x])
    and img[x][y]=target then
        img[x][y] = colour
        img = ff(img,x-1,y,colour,target)
        img = ff(img,x+1,y,colour,target)
        img = ff(img,x,y-1,colour,target)
        img = ff(img,x,y+1,colour,target)
    end if
    return img
end function

function FloodFill(sequence img, integer x, y, colour)
    integer target = img[x][y]
    return ff(img,x,y,colour,target)
end function

sequence img = read_ppm("Circle.ppm")
img = FloodFill(img, 200, 100, blue)
write_ppm("FloodIn.ppm",img)
img = FloodFill(img, 10, 10, green)
write_ppm("FloodOut.ppm",img)