Some Random Image API

local function log2(num)
    return math.log(num)/math.log(2)
end

local function dump(tbl, indent)
    local indent = indent or 0
    for k,v in pairs(tbl) do
        if(type(v) == "table") then
            dump(v,indent+1)
        else
            print(string.rep(" ",indent)..k.. " "..v)
        end
    end
end

-------------------------------------------
-- Thanks for this, Lignum :)            --
-------------------------------------------
local function unify(bgColour, fgColour)
  local bg = log2(bgColour)
  local fg = log2(fgColour)

  local field = bit.bor(bg, bit.blshift(fg, 4))
  return field
end

local function extractColors(bitfield)
  local bg = 2^(bit.band(bitfield, 0xF))
  local fg = 2^(bit.brshift(bitfield, 4))
  return bg, fg
end
-------------------------------------------


-------------------------------------------
-- Intended for conversion and stuff.    --
-- But not yet implemented.              --
-------------------------------------------
local colorChars = "0123456789abcdef"

local function getCharForColor(col)
    local c = log2(col)+1
    return colorChars:sub(c,c)
end

local function getColorForChar(ch)
    for i = 1,16 do
        if(colorChars:sub(i,i) == ch) then
            return 2^(i-1)
        end
    end
end
-------------------------------------------

local function getDimension(data)
    local h = #data
    local w = 0
    for k,v in pairs(data) do
        if(#v>w) then w = #v end
    end
    return w,h
end

local function isValid(data)
    local w = #data[1] --This is the reference width. Everything which is not equal to w is not valid.
    for k,v in pairs(data) do
        if(#v ~= w) then
            printError("Row "..k.." has an invalid length. Expected: "..w.." Got: "..#v)
            return false
        end
    end
    return true
end

function load(path)
    local content = {}
    local handle = fs.open(path,"rb")
    local currentLine = {}
    local isChar = false
    local w,h = handle.read(),handle.read()
    local linePos = 0
    for byte in handle.read do
        if(isChar) then
            currentLine[#currentLine][3] = string.char(byte)
            isChar = false
            linePos = linePos + 1
        else
            currentLine[#currentLine+1] = {extractColors(byte)}
            isChar = true
        end
        if(linePos == w) then
            table.insert(content,currentLine)
            currentLine = {}
            isChar = false
            linePos = 0
        end
    end
    print(#content)
    handle.close()
    return content
end

function draw(img)
    for y,line in pairs(img) do
        for x,char in pairs(line) do
            term.setCursorPos(x,y)
            term.setBackgroundColor(char[1])
            term.setTextColor(char[2])
            term.write(char[3])
        end
    end
end

function save(data,file)
    local handle = fs.open(file,"wb")
    local w,h = getDimension(data)
    handle.write(w)
    handle.write(h)
    for _y,y in pairs(data) do
        for _x,x in pairs(y) do
            handle.write(unify(x[1],x[2]))
            handle.write(x[3] ~= nil and string.byte(x[3]) or string.byte(" "))
        end
    end
    handle.close()
end