get("#388") -- rect functions
get("#348") -- rgb functions
get("#356") -- num2hex
get("#430") -- makeIcon
get("#428") -- findContents
get("#431") -- LXTerminal character reference
get("#433") -- iconDiff

function getIconSize(icon)
  local i = 1
  while string.sub(icon, i, i) ~= '.' do
    i = i+1
  end
  local w = i-1
  -- #icon+1 = (w+1)*h
  -- => h = (#icon+1)/(w+1)
  local h = (#icon+1)/(w+1)
  return w, h
end

fw_, fh_ = getIconSize(characterReference[1][2])
print("fw/fh", fw_, fh_)

function recognizeChar(icon)
  local best, min
  for _, ic in ipairs(characterReference) do
    local c, reficon = unpack(ic)
    local diff
    if min ~= nil then
      diff = iconDiffWithLimit(icon, reficon, min, fw_, fh_)
    else
      diff = iconDiff(icon, reficon)
    end
    --print("c", c, "diff", diff, "reficon", reficon)
    if diff ~= nil and (min == nil or diff < min) then
      best, min = c, diff
    end
  end
  return best, min
end

return function()
  local problem = findContents()
  if problem then return --[[problem]] end
  
  local fw, fh = 8, 17 -- font width/height
  local tw = math.floor((contents_x2-contents_x1)/fw+0.5)
  local th = math.floor((contents_y2-contents_y1)/fh+0.5)
  print("Terminal size: "..tw.."*"..th)
  
  local tbl = {}
  local maxdiff, maxc
  for y = 0, th-1 do
    line = {}
    for x = 0, tw-1 do
      local xx, yy = contents_x1+x*fw+1, contents_y1+y*fh
      local cropped = {width=fw-1, height=fh-1,
        getInt = function(x, y) return img.getInt(xx+x, yy+y) end}
      local icon = makeIcon(cropped)
      local c, diff = recognizeChar(icon)
      if maxdiff == nil or diff > maxdiff then
        maxdiff, maxc = diff, c
      end
      --print("c: "..tostring(c)..", diff: "..tostring(diff)..", icon: "..icon)
      table.insert(line, c or "?")
    end
    table.insert(tbl, table.concat(line))
  end
  
  print("maxdiff", maxdiff, "c", maxc)
  
  return "Screen text:\n"..table.concat(tbl, "\n")
end

Began life as a copy of #432