get("#348") -- rgb functions
get("#346") -- getcrop
get("#337") -- map(list, f)

w, h = img.width, img.height
brightnessThreshold = 0.9

function isEmpty(y)
  for x=0, w-1 do
    if bright(rgb(img.getInt(x, y))) <= brightnessThreshold then
      return false
    end
  end
  return true
end

lastEmpty = true
segments = {}

for y=0, h-1 do
  empty = isEmpty(y)
  if empty and not lastEmpty then
    table.insert(segments, {start, y})
  elseif not empty and lastEmpty then
    start = y
  end
  lastEmpty = empty
end

if not lastEmpty then
  table.insert(segments, {start, h})
end

if #segments <= 1 then -- don't bother with only 1 segment
  return
end

result = {}
for _, seg in ipairs(segments) do
  local sy1, sy2 = unpack(seg)
  
  local cropped = {
    width = img.width,
    height = sy2-sy1,
    getInt = function(x, y)
      return img.getInt(x, y+sy1)
    end
  }
  local x1, y1, x2, y2 = getcrop(cropped)
  table.insert(result, x1..", "..(y1+sy1)..", "..x2..", "..(y2+sy1))
end

return "Parts: "..table.concat(result, "|")

Began life as a copy of #345