get("#348") 
w, h = img.width, img.height

tbl = {}
for y = 0, h-1 do
  sum = 0
  for x = 0, w-1 do
    sum = sum+bright(rgb(img.getInt(x, y)))
  end
  sum = sum/w
  print("y", y, "heat", sum)
  table.insert(tbl, string.char(string.byte("A")+math.floor(sum*25+0.5)))
end

return "Heat map (vertical): "..table.concat(tbl)