Lua/LuaGD Image Plotting for Powder Toy

require "gd"
function gdplot(file, itype)
    --Get image type
    itype = string.sub(file, -4, -1)
    itype = string.gsub(itype, '%.', '')
    --Open image
    if itype == 'jpeg' or itype == 'jpg' then
        im = gd.createFromJpeg(file)
    elseif itype == 'png' then
        im = gd.createFromPng(file)
    elseif itype == 'gif' then
        im = gd.createFromGif(file)
    end
    --Height, width
    local w, h = im:sizeXY()
    --is it bigger than the screen?
    if w >= 610 then
        w = 610
    end
    if h > 380 then
        h = 380
    end
    --Run through the image
    for x = 0, w do
        for y = 0, h do
            --Get color as hex string...
            color = tostring(bit.tohex(im:getPixel(x, y)))
            --and take the r, g, b individual values.
            r = string.sub(color, 3, 4)
            g = string.sub(color, 5, 6)
            b = string.sub(color, 7, 8)
            --Draw a pixel
            tpt.create(x, y, "dmnd")
            tpt.set_property("dcolor", '0xFF' .. r .. g .. b, x, y)
        end
    end
end