tga_encoder = {} local image = setmetatable({}, { __call = function(self, ...) local t = setmetatable({}, {__index = self}) t:constructor(...) return t end, }) function image:constructor(pixels) self.data = "" self.pixels = pixels self.width = #pixels[1] self.height = #pixels self:encode() end function image:encode_colormap_spec() self.data = self.data .. string.char(0, 0) -- first entry index .. string.char(0, 0) -- number of entries .. string.char(0) -- bits per pixel end function image:encode_image_spec() self.data = self.data .. string.char(0, 0) -- X-origin .. string.char(0, 0) -- Y-origin .. string.char(self.width % 256, math.floor(self.width / 256)) -- width .. string.char(self.height % 256, math.floor(self.height / 256)) -- height .. string.char(24) -- pixel depth (RGB = 3 bytes = 24 bits) .. string.char(0) -- image descriptor end function image:encode_header() self.data = self.data .. string.char(0) -- image id .. string.char(0) -- color map type .. string.char(10) -- image type (RLE RGB = 10) self:encode_colormap_spec() -- color map specification self:encode_image_spec() -- image specification end function image:encode_data() local current_pixel = '' local previous_pixel = '' local count = 1 local packets = {} local rle_packet = '' for _, row in ipairs(self.pixels) do for _, pixel in ipairs(row) do current_pixel = string.char(pixel[3], pixel[2], pixel[1]) if current_pixel ~= previous_pixel or count == 128 then packets[#packets +1] = rle_packet count = 1 previous_pixel = current_pixel else count = count + 1 end rle_packet = string.char(128 + count - 1) .. current_pixel end end packets[#packets +1] = rle_packet self.data = self.data .. table.concat(packets) end function image:encode_footer() self.data = self.data .. string.char(0, 0, 0, 0) -- extension area offset .. string.char(0, 0, 0, 0) -- developer area offset .. "TRUEVISION-XFILE" .. "." .. string.char(0) end function image:encode() self:encode_header() -- header -- no color map and image id data self:encode_data() -- encode data -- no extension or developer area self:encode_footer() -- footer end function image:save(filename) local f = assert(io.open(filename, "w")) f:write(self.data) f:close() end tga_encoder.image = image