get("#121") -- compareTables

get("#348") -- bright and rgb

maxSize = {width=100, height=50}

minSize = {width=4, height=4}

threshold = 0.5

wandSize = 2 -- magic wand size

local rectangles, img

function cloneRectangle(r)

  return newRectangle(r.x, r.y, r.width, r.height)

end

function newRectangle(x, y, w, h)

  return {x=x, y=y, width=w, height=h}

end

function contains(r, x, y)

  return x >= r.x and y >= r.y and x < r.x+r.width and y < r.y+r.width

end

function seen(x, y)

  for r, _ in pairs(rectangles) do

    if contains(r, x, y) then

      return true

    end

  end

return false

end

-- returns rectangle

function magicWand(image, x, y)

  if image ~= img then

    img, rectangles = image, {}

  end

  if seen(x, y) then return nil end

  local r = newRectangle(x, y, 1, 1)

  while true do

    local last = cloneRectangle(r)

    expandLeft(image, r)

    if tooLarge(r) then return nil end

    expandTop(image, r)

    if tooLarge(r) then return nil end

    expandRight(image, r)

    if tooLarge(r) then return nil end

    expandBottom(image, r)

    if tooLarge(r) then return nil end

    if compareTables(last, r) then

      if r.width >= minSize.width and r.height >= minSize.width then

        rectangles[r] = true

        return r

      else

        return nil

      end

    end

  end

end

function tooLarge(r)

  return maxSize ~= nil and (r.width > maxSize.width or r.height > maxSize.height)

end

function expandLeft(image, r)

  local newX = math.max(r.x - wandSize, 0)

  if newX == r.x then return end

  newX = searchFromLeft(image, newRectangle(newX, r.y, r.x-newX, r.height))

  r.width = r.width+r.x-newX

  r.x = newX

end

function searchFromLeft(image, r)

  for x = r.x, r.x+r.width-1 do

    if regionNotEmpty(image, newRectangle(x, r.y, 1, r.height)) then

      return x

    end

  end

  return r.x+r.width

end

function expandRight(image, r)

  local newX = math.min(r.x + r.width + wandSize, image.width)

  if newX == r.x+r.width then return end

  newX = searchFromRight(image, newRectangle(r.x+r.width, r.y, newX-(r.x+r.width), r.height))

  r.width = newX-r.x

end

function searchFromRight(image, r)

  for x = r.x+r.width-1, r.x, -1 do

    if regionNotEmpty(image, newRectangle(x, r.y, 1, r.height)) then

      return x+1

    end

  end

  return r.x

end

function expandTop(image, r)

  local newY = math.max(r.y - wandSize, 0)

  if newY == r.y then return end

  newY = searchFromTop(image, newRectangle(r.x, newY, r.width, r.y-newY))

  r.height = r.height+r.y-newY

  r.y = newY

end

function searchFromTop(image, r)

  for y = r.y, r.y+r.height-1 do

    if regionNotEmpty(image, newRectangle(r.x, y, r.width, 1)) then

      return y

    end

  end

  return r.y+r.height

end

function expandBottom(image, r)

  local newY = math.min(r.y + r.height + wandSize, image.height)

  if newY == r.y+r.height then return end

  newY = searchFromBottom(image, newRectangle(r.x, r.y + r.height, r.width, newY-(r.y+r.height)))

  r.height = newY-r.y

end

function searchFromBottom(image, r)

  for y = r.y+r.height-1, r.y, -1 do

    if regionNotEmpty(image, newRectangle(r.x, y, r.width, 1)) then

      return y+1

    end

  end

  return r.y

end

-- we're looking for dark pixels this time

function regionNotEmpty(image, r)

  --return image.clip(rectangle).anyPixelBrighterThan(threshold)

  for y=r.y, r.y+r.height-1 do

    for x=r.x, r.x+r.width-1 do

      if bright(rgb(image.getInt(x, y))) < threshold then

        return true

      end

    end

  end

  return false

end

function recttostring(r)

  return r.x..", "..r.y..", "..r.x+r.width..", "..r.y+r.height

end

function magicWandAll(image)

  local allrects = {}

  for y = 0, image.height-1, 2 do

    for x = 0, image.width-1, 2 do

      local r = magicWand(image, x, y)

      if r then

        allrects[recttostring(r)] = true

      end

    end

  end

  return allrects

end