NfpToBmp.lua

local Args = {...}

if #Args < 2 then
    printError("Usage: Nfp2Bmp <InputFile> <OutputFile> [Background-Colour-Name]")
    printError("Usage: Nfp2Bmp <InputFile> <OutputFile> [Backg-R] [Back-G] [Back-B]")
    error()
end

local Colours = {
    {240, 240, 240},    -- colors.white
    {242, 178, 51},     -- colors.orange
    {229, 127, 216},    -- colors.magenta
    {153, 178, 242},    -- colors.lightBlue
    {222, 222, 108},    -- colors.yellow
    {127, 204, 25},     -- colors.lime
    {242, 178, 204},    -- colors.pink
    {76, 76, 76},       -- colors.gray
    {153, 153, 153},    -- colors.lightGray
    {76, 153, 178},     -- colors.cyan
    {178, 102, 229},    -- colors.purple
    {37, 49, 146},      -- colors.blue
    {127, 102, 76},     -- colors.brown
    {5, 122, 100},      -- colors.green
    {204, 76, 76},      -- colors.red
    {0, 0, 0},          -- colors.black
}

local ColourLookup = {
    ["0"] = 0,
    ["1"] = 1,
    ["2"] = 2,
    ["3"] = 3,
    ["4"] = 4,
    ["5"] = 5,
    ["6"] = 6,
    ["7"] = 7,
    ["8"] = 8,
    ["9"] = 9,
    ["a"] = 10,
    ["b"] = 11,
    ["c"] = 12,
    ["d"] = 13,
    ["e"] = 14,
    ["f"] = 15,
    [" "] = 16,
}


local Colour = {0, 0, 0}
if #Args == 3 then
    --Actually log(x, 2) so colours.white = 1 => log(1, 2) = 0
    --Applies for other colours
    Colour = math.log(colours[Args[3]]) / math.log(2)
elseif #Args == 5 then
    Colour = {tonumber(Args[3]), tonumber(Args[4]), tonumber(Args[5])}
end

table.insert(Colours, Colour)


local Pixels = {}

local Input = fs.open(Args[1], "r")

local Width = 0
local Height = 0

local Line = Input.readLine()
while Line do
    local Row = {}

    for X=1, Line:len() do
        Row[X] = ColourLookup[string.sub(Line, X, X)] or 16
    end

    Width = math.max(Width, #Row)

    table.insert(Pixels, Row)
    Line = Input.readLine()
end

Input.close()

Height = #Pixels


local Output = fs.open(Args[2], "wb")

function Write(Number, Size)
    while Size > 0 do
        Output.write(Number % 256)

        Number = math.floor(Number / 256)
        Size = Size - 1
    end
end


--Bitmap header

Output.write(66)    --B
Output.write(77)    --M

--How big are we?
-- 54 for total headers + 256 * 4 for colour map
Write(1078 + (Width * Height), 4)

for _=1,4,1 do
    Output.write(0)
end

--When do we start the actual content?
-- 54 for total headers + 256 * 4 for colour map
Write(1078, 4)

--DIB Header
Write(40, 4)

Write(Width, 4)
Write(Height, 4)

Write(1, 2) --Colour planes

Write(8, 2)
--Compression (none) (4 bytes)
--Size (not needed if no compression) (4 bytes)
--Resolution Horizontal (4 bytes) and Vertical (4 bytes)
--Number of colours (4 bytes)
--Number of important colours (4 bytes)
for _=1,24,1 do
    Output.write(0)
end

--Colour table!
for I=1, 256, 1 do
    local Colour = Colours[I]

    if Colour == nil then
        for _=1,4,1 do
            Output.write(0)
        end
    else
        Output.write(Colour[3])     --Goes BGR for silly reason
        Output.write(Colour[2])
        Output.write(Colour[1])
        Output.write(0)
    end
end

for Y = Height, 1, -1 do
    local Row = Pixels[Y]
    local Counter = 0

    for X = 1, Width, 1 do
        Counter = (Counter + 1) % 4
        Output.write(Row[X])
    end

    if Counter ~= 0 then
        for I=Counter, 3 do
            Output.write(0)
        end
    end
end

Output.close()