CBM Library

local tags = {"&f", "&6", "&f", "&b", "&e",  "&a", "&d", "&8", "&7", "&3", "&5", "&1", "&f", "&2", "&c", "&0"}
local reverseTags = {}
for k,v in pairs(tags) do
    reverseTags[v] = k-1
end

function loadCBM(sFile, useTags, noAnimation)
    if (not fs.exists(sFile)) or fs.isDir(sFile)
        then return nil, "Invalid file or directory"
    else
        local file = fs.open(sFile, "rb")
        if not file then return nil, "Invalid file or directory 2" end
        --[[local]] bytes = {}
        byteCopy = {}
        while true do
            local byte = file.read()
            if not byte then break end
            table.insert(bytes, byte)
            table.insert(byteCopy, byte)
        end
        file.close()
        --[[local]] width, height = 0, 0
        if #bytes < 12 then return nil, "Invalid image" end
        for i=1,3 do
            if table.remove(bytes,1) ~= string.byte("CBM", i) then return nil, "Not a CBM file" end
        end
        for byteNum=3,0,-1 do
            height = height + (2^byteNum)*table.remove(bytes,1)
        end
        for byteNum=3,0,-1 do
            width = width + (2^byteNum)*table.remove(bytes,1)
        end
        --[[local]] flags = table.remove(bytes, 1)
        --[[local]] trans = bit.band(flags, 1) ~= 0; flags = bit.brshift(flags, 1)
        --[[local]] animated = bit.band(flags, 1) ~= 0; flags = bit.brshift(flags, 1)
        --[[local]] reps = table.remove(bytes, 1)
        --[[local]] interval = table.remove(bytes, 1) + 1
        --[[local]] imgBytes = math.ceil(width*height/2)
        --[[local]] alphaBytes = trans and math.ceil(width*height/8) or 0
        if #bytes%(imgBytes+alphaBytes)~=0 then return nil, "Invalid image 2" end
        local frameNum = animated and #bytes/(imgBytes+alphaBytes) or 1
        local frames = {}
        for _=1,noAnimation and 1 or frameNum do
            local pixels = {}
            local pixelList = {}
            local bitMask = {}
            for i=1,imgBytes do
                local byte = table.remove(bytes, 1)
                table.insert(pixelList, 1, math.floor(byte/16))
                table.insert(pixelList, 1, byte%16)
                if useTags then
                    for i=1,2 do
                        pixelList[i] = tags[pixelList[i]+1]
                    end
                end
            end
            if trans then
                for i=1,alphaBytes do
                    local insertPoint = #bitMask + 1
                    local byte = table.remove(bytes, 1)
                    for j=1,8 do
                        --[[if ((i-1)*8)+j<=width*height then]] table.insert(bitMask, insertPoint, bit.band(byte, 1)) --end
                        bit.brshift(byte, 1)
                    end
                end
            end
            if (width*height)%2 == 1 then pixelList[#pixelList] = nil end
            for row=1,height do
                pixels[row] = {}
                for column=1,width do
                    pixels[row][column] = table.remove(pixelList)
                    if trans then
                        if table.remove(bitMask, 1) == 1 then
                            pixels[row][column] = -1
                        end
                    end
                end
            end
            table.insert(frames, pixels)
        end
        if not noAnimation then frames.interval = interval end
        if not noAnimation then frames.repetitions = (reps == 0) and math.huge or reps end
        return noAnimation and frames[1] or frames
    end
end

function saveCBM( sFile, frames, trans)
    t = trans
    function toBytes(number, byteCount)
        local byteCount = byteCount or 4
        local byteTable = {}
        for _=1,byteCount do
            table.insert(byteTable, 1, number%256)
            number=(number-byteTable[1])/256
        end
        return byteTable
    end
    if not (frames and sFile) then return nil, "Invalid argument" end
    local reps = frames.repetitions or 0
    if reps == math.huge then reps = 0 end
    if reps > 255 then reps = 255 end
    local interval = frames.interval or 10
    if interval > 255 then interval = 255 end
    --[[local]] animated = type(frames[1][1]) == "table"
    local bytes = {string.byte("CBM", 1, 3)}
    local pixels = animated and frames[1] or frames
    frames = animated and frames or {frames}
    local height = #pixels
    if height == 0 then return nil, "Empty image" end
    local width = #pixels[1]
    for i=2,height do
        if #pixels[i] ~= width then return nil, "Invalid image" end
    end
    local widthBytes = toBytes(width)
    local heightBytes = toBytes(height)
    for i=1,4 do
        table.insert(bytes, heightBytes[i])
    end
    for i=1,4 do
        table.insert(bytes, widthBytes[i])
    end
    --[[local]] flags = 0
    flags = flags + (animated and 1 or 0)
    flags = bit.blshift(flags, 1); flags = flags + (trans and 1 or 0)
    table.insert(bytes, flags)
    table.insert(bytes, reps)
    table.insert(bytes, interval)
    for _,pixels in ipairs(frames) do
        local bitMask = {}
        for row = 1,height do
            for column = 1,width,2 do
                pixels[row][2] = pixels[row][2] or 0
                for i=1,2 do
                    if type(pixels[row][i]) ~= "number" then
                        if string.sub(pixels[row][i],1,1) == "&" then
                            pixels[row][i] = reverseTags[pixels[row][i]]
                        else return nil, "Invalid pixel: "..row..", "..column+i-1
                        end
                    end
                end
                if pixels[row][1] > 15 or pixels[row][2]  > 15 or pixels[row][1] < -1 or pixels[row][2] < -1 then return nil, "Invalid pixel 2: "..row..", "..column end
                if pixels[row][1] == -1 then pixels[row][1] = 0 table.insert(bitMask, 1) else table.insert(bitMask, 0) end
                if pixels[row][2] == -1 then pixels[row][2] = 0 table.insert(bitMask, 1) else table.insert(bitMask, 0) end
                table.insert(bytes, table.remove(pixels[row],1)*16 + table.remove(pixels[row],1))
            end
        end
        while #bitMask%8~=0 do table.insert(bitMask, 0) end
        if trans then
            for i=1,#bitMask,8 do
                local byte = 0
                for j=0,7 do
                byte = byte + 2^(7-j) * bitMask[i+j]
            end
                table.insert(bytes, byte)
            end
        end
    end
    local yieldcount = 0
    local file = fs.open(sFile, "wb")
    for _,byte in ipairs(bytes) do
        yieldcount = yieldcount + 1
        if yieldcount >= 64 then os.queueEvent(".") os.pullEvent(".") yieldcount = 0 end
        file.write(byte)
    end
    file.close()
    return true
end