scanline-fill algorithm written in Ruby (non-recursive version)
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# Scanline-fill <James.Lopez at bluegod.net> | |
# GPLv2 License | |
# I've based this method on: | |
# http://en.wikipedia.org/wiki/Flood_fill#Scanline_fill | |
# Seems the most efficient way as alternatives: | |
# Recursion: Stack overflow problem | |
# Pixel by pixel: at least 1 order of magnitude less efficient. | |
# | |
# https://github.com/bluegod/scanlinefill | |
def fill_scanline_fast(x_coord, y_coord, oldColour, newColour) | |
return if newColour == oldColour | |
#Create a new stack to pop/push values up to a maximum value. | |
stack = Stack.new | |
#Values passed start from 1, you may need to modify this if the start from zero. | |
y = x_coord - 1 | |
x = y_coord - 1 | |
stack.push([x, y]) | |
while (!stack.empty?) | |
#Get the next value | |
x,y = stack.pop | |
y1 = y | |
#Scan y1 to the left | |
while (y1 >= 0 && @img[x][y1] == oldColour) | |
y1-=1 | |
end | |
y1+=1 | |
east, west = false, false | |
#Fills in lines the neighbour pixels | |
while (y1 < img_x && @img[x][y1] == oldColour) | |
#Set new colour | |
@img[x][y1] = newColour | |
if (!east && x > 0 && @img[x - 1][y1] == oldColour) | |
stack.push([x-1, y1]) | |
east = true | |
elsif (east && x > 0 && @img[x - 1][y1] != oldColour) | |
east = false | |
end | |
if (!west && x < img_y - 1 && @img[x + 1][y1] == oldColour) | |
stack.push([x + 1, y1]) | |
west = true | |
elsif (west && x < img_y - 1 && @img[x + 1][y1] != oldColour) | |
west = false | |
end | |
y1+=1 | |
end | |
end | |
end |
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