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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(2) -- image type (uncompressed true-color image = 2)
self:encode_colormap_spec() -- color map specification
self:encode_image_spec() -- image specification
end
function image:encode_data()
for _, row in ipairs(self.pixels) do
for _, pixel in ipairs(row) do
self.data = self.data
.. string.char(pixel[3], pixel[2], pixel[1])
end
end
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
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