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tga_encoder = {}
local LUA_ARGS_LIMIT = 1000
local image = setmetatable({}, {
__call = function(self, ...)
local t = setmetatable({}, {__index = self})
t:constructor(...)
return t
end,
})
function image:constructor(pixels)
self.bytes = {}
self.chunks = {self.bytes}
self.pixels = pixels
self.width = #pixels[1]
self.height = #pixels
self:encode()
end
function image:insert(byte)
table.insert(self.bytes, byte)
if #self.bytes == LUA_ARGS_LIMIT then
self.bytes = {}
table.insert(self.chunks, self.bytes)
end
end
function image:littleendian(size, value)
for i = 1, size do
local byte = value % 256
value = value - byte
value = value / 256
self:insert(byte)
end
end
function image:encode_colormap_spec()
-- first entry index
self:littleendian(2, 0)
-- number of entries
self:littleendian(2, 0)
-- number of bits per pixel
self:insert(0)
end
function image:encode_image_spec()
-- X- and Y- origin
self:littleendian(2, 0)
self:littleendian(2, 0)
-- width and height
self:littleendian(2, self.width)
self:littleendian(2, self.height)
-- pixel depth
self:insert(24)
-- image descriptor
self:insert(0)
end
function image:encode_header()
-- id length
self:insert(0) -- no image id info
-- color map type
self:insert(0) -- no color map
-- image type
self:insert(2) -- uncompressed true-color image
-- color map specification
self:encode_colormap_spec()
-- image specification
self:encode_image_spec()
end
function image:encode_data()
for _, row in ipairs(self.pixels) do
for _, pixel in ipairs(row) do
self:insert(pixel[3])
self:insert(pixel[2])
self:insert(pixel[1])
end
end
end
function image:encode()
-- encode header
self:encode_header()
-- no color map and image id data
-- encode data
self:encode_data()
-- no extension area
end
function image:get_data()
local data = ""
for _, bytes in ipairs(self.chunks) do
data = data .. string.char(unpack(bytes))
end
return data .. string.char(0, 0, 0, 0) .. string.char(0, 0, 0, 0) .. "TRUEVISION-XFILE." .. string.char(0)
end
function image:save(filename)
self.data = self.data or self:get_data()
local f = assert(io.open(filename, "w"))
f:write(self.data)
f:close()
end
tga_encoder.image = image
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