mirror of
https://github.com/HybridDog/vector_extras.git
synced 2024-11-15 06:50:35 +01:00
117 lines
1.9 KiB
Lua
117 lines
1.9 KiB
Lua
-- http://www.adammil.net/blog/v126_A_More_Efficient_Flood_Fill.html
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local can_go
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local marked_places
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local function calc_2d_index(x, y)
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return (y + 32768) * 65536 + x + 32768
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end
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local function mark(x, y)
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marked_places[calc_2d_index(x, y)] = true
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end
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local _fill
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local function fill(x, y)
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if can_go(x, y) then
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_fill(x, y)
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end
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end
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local corefill
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function _fill(x, y)
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while true do
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local ox = x
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local oy = y
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while can_go(x, y-1) do
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y = y-1
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end
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while can_go(x-1, y) do
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x = x-1
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end
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if x == ox
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and y == oy then
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break
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end
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end
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corefill(x, y)
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end
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function corefill(x, y)
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local lastcnt = 0
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repeat
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local cnt = 0
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local sx = x
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if lastcnt ~= 0
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and not can_go(y, x) then
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-- go right to find the x start
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repeat
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lastcnt = lastcnt-1
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if lastcnt == 0 then
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return
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end
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x = x+1
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until can_go(x, y)
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sx = x
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else
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-- go left if possible, and mark and _fill above
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while can_go(x-1, y) do
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x = x-1
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mark(x, y)
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if can_go(x, y-1) then
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_fill(x, y-1)
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end
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cnt = cnt+1
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lastcnt = lastcnt+1
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end
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end
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-- go right if possible, and mark
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while can_go(sx, y) do
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mark(sx, y)
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cnt = cnt+1
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sx = sx+1
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end
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if cnt < lastcnt then
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local e = x + lastcnt
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sx = sx+1
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while sx < e do
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if can_go(sx, y) then
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corefill(sx, y)
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end
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sx = sx+1
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end
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elseif cnt > lastcnt then
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local ux = x + lastcnt + 1
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while ux < sx do
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if can_go(ux, y-1) then
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_fill(ux, y-1)
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end
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ux = ux+1
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end
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end
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lastcnt = cnt
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y = y+1
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until lastcnt == 0
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end
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local function apply_fill(go_test, x0, y0, allow_revisit)
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if allow_revisit then
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can_go = go_test
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else
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local visited = {}
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can_go = function(x, y)
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local vi = calc_2d_index(x, y)
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if visited[vi] then
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return false
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end
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visited[vi] = true
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return go_test(x, y)
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end
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end
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marked_places = {}
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fill(x0, y0)
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return marked_places
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end
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return apply_fill
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