Projection (Updated Paint)

--[[INSTRUCTIONS:
        pixels in upper-right corner represent color selection.
        left = text color.
        middle = background color (leftClick).
        right = alternate background color (rightClick).

        click on an upper-right pixel and use shift/control to cycle through its colors.
        press any keyboard character to select it.
        use mouseclick/drag to paint.
        press alt to exit.
    ]]

local w,h = term.getSize()

function switchColors()
  local alphabet = {"a","b","c","d","e","f"}
  for i,v in pairs(colors) do
    if tonumber(v) then
      res = math.log(v)/math.log(2)
      if res > 9 then
        res = alphabet[res-9]
      end
      colors[i] = tostring(res)
    end
  end
end

function draw(str,xPos,yPos,txtcol,bakcol)
  local str = tostring(str) or ""
  local txtcol = txtcol or txtsel
  local bakcol = bakcol or baksel
  if xPos and yPos then
    term.setCursorPos(xPos, yPos)
  end
  if term.blit then
    term.blit(str,string.rep(txtcol,#str),string.rep(bakcol,#str))
  else
    term.setBackgroundColor(bakcol)
    term.setTextColor(txtcol)
    term.write(str)
  end
end

if term.blit then
    switchColors()
else
    os.loadAPI(shell.resolve("rom/apis/colors"))
end

term.clear()
baksel = colors.yellow
txtsel = colors.white
altsel = colors.black

local pallet = {}
n = 0
for i,v in pairs(colors) do
    if tonumber(v) then
      n = n + 1
      pallet[n] = v
    end
end

local sel = 'bak'
local nCol = 1
local tCol = 1
local aCol = 1
local key = " "
while true do
    local events = {coroutine.yield()}
    if events[1] == "mouse_click" or events[1] == "mouse_drag" then
        if events[2] == 1 then
            if events[3] == w-1 and events[4] == 1 then
                sel = 'txt'
            elseif events[3] == w-2 and events[4] == 1 then
                sel = 'bak'
            elseif events[3] == w and events[4] == 1 then
                sel = 'alt'
            else
              draw(key,events[3],events[4])
            end
        elseif events[2] == 2 then
            draw(key,events[3],events[4],txtsel,altsel)
        end
    elseif events[1] == "char" then
        key = tostring(events[2])
    --[[elseif events[1] == "mouse_scroll" then
        if events[2] == 1 then
            if nCol < #pallet then
              nCol = nCol + 1
              baksel = pallet[nCol]
            end
        elseif events[2] == -1 then
            if nCol > 1 then
              nCol = nCol - 1
              baksel = pallet[nCol]
            end
        end]]
    elseif events[1] == "key" then
        if events[2] == 42 then
            if sel == 'txt' then
              if tCol < #pallet then
                tCol = tCol + 1
                txtsel = pallet[tCol]
              end
            elseif sel == 'bak' then
                if nCol < #pallet then
                    nCol = nCol + 1
                    baksel = pallet[nCol]
                end
            elseif sel == 'alt' then
                if aCol < #pallet then
                    aCol = aCol + 1
                    altsel = pallet[aCol]
                end
            end
        elseif events[2] == 29 then
            if sel == 'txt' then
              if tCol > 1 then
                tCol = tCol - 1
                txtsel = pallet[tCol]
              end
            elseif sel == 'bak' then
                if nCol > 1 then
                    nCol = nCol - 1
                    baksel = pallet[nCol]
                end
            elseif sel == 'alt' then
                if aCol > 1 then
                    aCol = aCol - 1
                    altsel = pallet[aCol]
                end
            end
        end
        elseif events[2] == 56 then
            break
        end
    draw(" ",w-1,1,_,txtsel)
    draw(" ",w-2,1)
    draw(" ",w,1,_,altsel)
end


for i,v in pairs(pallet) do
    print(i,": ",v)
end
print(#pallet)