forked from VoxeLibre/VoxeLibre
280 lines
8.2 KiB
Lua
280 lines
8.2 KiB
Lua
tga_encoder = {}
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local image = setmetatable({}, {
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__call = function(self, ...)
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local t = setmetatable({}, {__index = self})
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t:constructor(...)
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return t
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end,
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})
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function image:constructor(pixels)
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self.pixels = pixels
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self.width = #pixels[1]
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self.height = #pixels
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end
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function image:encode_colormap_spec()
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self.data = self.data
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.. string.char(0, 0) -- first entry index
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.. string.char(0, 0) -- number of entries
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.. string.char(0) -- bits per pixel
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end
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function image:encode_image_spec(properties)
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local colors = properties.colors
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local pixel_depth = properties.pixel_depth
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assert(
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"BW" == colors and 8 == pixel_depth or -- (8 bit grayscale = 1 byte = 8 bits)
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"RGB" == colors and 16 == pixel_depth or -- (A1R5G5B5 = 2 bytes = 16 bits)
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"RGB" == colors and 24 == pixel_depth -- (B8G8R8 = 3 bytes = 24 bits)
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)
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self.data = self.data
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.. string.char(0, 0) -- X-origin
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.. string.char(0, 0) -- Y-origin
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.. string.char(self.width % 256, math.floor(self.width / 256)) -- width
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.. string.char(self.height % 256, math.floor(self.height / 256)) -- height
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.. string.char(pixel_depth)
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.. string.char(0) -- image descriptor
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end
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function image:encode_header(properties)
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local colors = properties.colors
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local pixel_depth = properties.pixel_depth
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local image_type
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if "BW" == colors and 8 == pixel_depth then
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image_type = 3 -- grayscale
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elseif (
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"RGB" == colors and 16 == pixel_depth or
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"RGB" == colors and 24 == pixel_depth
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) then
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image_type = 10 -- RLE RGB
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end
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self.data = self.data
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.. string.char(0) -- image id
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.. string.char(0) -- color map type
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.. string.char(image_type)
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self:encode_colormap_spec() -- color map specification
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self:encode_image_spec(properties) -- image specification
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end
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function image:encode_data(properties)
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local colors = properties.colors
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local pixel_depth = properties.pixel_depth
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if "BW" == colors and 8 == pixel_depth then
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self:encode_data_bw8()
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elseif "RGB" == colors and 16 == pixel_depth then
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self:encode_data_a1r5g5b5_rle()
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elseif "RGB" == colors and 24 == pixel_depth then
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self:encode_data_r8g8b8_rle()
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end
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end
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function image:encode_data_bw8()
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local raw_pixels = {}
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for _, row in ipairs(self.pixels) do
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for _, pixel in ipairs(row) do
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local raw_pixel = string.char(pixel[1])
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raw_pixels[#raw_pixels + 1] = raw_pixel
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end
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end
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self.data = self.data .. table.concat(raw_pixels)
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end
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function image:encode_data_a1r5g5b5_rle()
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local colorword = nil
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local previous_r = nil
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local previous_g = nil
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local previous_b = nil
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local raw_pixel = ''
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local raw_pixels = {}
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local count = 1
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local packets = {}
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local raw_packet = ''
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local rle_packet = ''
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-- Sample depth rescaling is done according to the algorithm presented in:
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-- <https://www.w3.org/TR/2003/REC-PNG-20031110/#13Sample-depth-rescaling>
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local max_sample_in = math.pow(2, 8) - 1
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local max_sample_out = math.pow(2, 5) - 1
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for _, row in ipairs(self.pixels) do
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for _, pixel in ipairs(row) do
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if pixel[1] ~= previous_r or pixel[2] ~= previous_g or pixel[3] ~= previous_b or count == 128 then
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if nil ~= previous_r then
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colorword = 32768 +
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((math.floor((previous_r * max_sample_out / max_sample_in) + 0.5)) * 1024) +
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((math.floor((previous_g * max_sample_out / max_sample_in) + 0.5)) * 32) +
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((math.floor((previous_b * max_sample_out / max_sample_in) + 0.5)) * 1)
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if 1 == count then
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-- remember pixel verbatim for raw encoding
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raw_pixel = string.char(colorword % 256, math.floor(colorword / 256))
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raw_pixels[#raw_pixels + 1] = raw_pixel
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if 128 == #raw_pixels then
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raw_packet = string.char(#raw_pixels - 1)
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packets[#packets + 1] = raw_packet
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for i=1, #raw_pixels do
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packets[#packets +1] = raw_pixels[i]
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end
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raw_pixels = {}
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end
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else
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-- encode raw pixels, if any
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if #raw_pixels > 0 then
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raw_packet = string.char(#raw_pixels - 1)
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packets[#packets + 1] = raw_packet
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for i=1, #raw_pixels do
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packets[#packets +1] = raw_pixels[i]
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end
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raw_pixels = {}
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end
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-- RLE encoding
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rle_packet = string.char(128 + count - 1, colorword % 256, math.floor(colorword / 256))
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packets[#packets +1] = rle_packet
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end
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end
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count = 1
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previous_r = pixel[1]
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previous_g = pixel[2]
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previous_b = pixel[3]
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else
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count = count + 1
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end
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end
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end
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colorword = 32768 +
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((math.floor((previous_r * max_sample_out / max_sample_in) + 0.5)) * 1024) +
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((math.floor((previous_g * max_sample_out / max_sample_in) + 0.5)) * 32) +
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((math.floor((previous_b * max_sample_out / max_sample_in) + 0.5)) * 1)
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if 1 == count then
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raw_pixel = string.char(colorword % 256, math.floor(colorword / 256))
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raw_pixels[#raw_pixels + 1] = raw_pixel
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raw_packet = string.char(#raw_pixels - 1)
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packets[#packets + 1] = raw_packet
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for i=1, #raw_pixels do
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packets[#packets +1] = raw_pixels[i]
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end
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raw_pixels = {}
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else
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-- encode raw pixels, if any
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if #raw_pixels > 0 then
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raw_packet = string.char(#raw_pixels - 1)
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packets[#packets + 1] = raw_packet
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for i=1, #raw_pixels do
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packets[#packets +1] = raw_pixels[i]
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end
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raw_pixels = {}
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end
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-- RLE encoding
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rle_packet = string.char(128 + count - 1, colorword % 256, math.floor(colorword / 256))
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packets[#packets +1] = rle_packet
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end
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self.data = self.data .. table.concat(packets)
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end
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function image:encode_data_r8g8b8_rle()
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local previous_r = nil
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local previous_g = nil
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local previous_b = nil
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local raw_pixel = ''
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local raw_pixels = {}
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local count = 1
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local packets = {}
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local raw_packet = ''
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local rle_packet = ''
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for _, row in ipairs(self.pixels) do
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for _, pixel in ipairs(row) do
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if pixel[1] ~= previous_r or pixel[2] ~= previous_g or pixel[3] ~= previous_b or count == 128 then
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if nil ~= previous_r then
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if 1 == count then
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-- remember pixel verbatim for raw encoding
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raw_pixel = string.char(previous_b, previous_g, previous_r)
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raw_pixels[#raw_pixels + 1] = raw_pixel
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if 128 == #raw_pixels then
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raw_packet = string.char(#raw_pixels - 1)
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packets[#packets + 1] = raw_packet
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for i=1, #raw_pixels do
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packets[#packets +1] = raw_pixels[i]
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end
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raw_pixels = {}
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end
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else
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-- encode raw pixels, if any
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if #raw_pixels > 0 then
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raw_packet = string.char(#raw_pixels - 1)
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packets[#packets + 1] = raw_packet
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for i=1, #raw_pixels do
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packets[#packets +1] = raw_pixels[i]
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end
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raw_pixels = {}
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end
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-- RLE encoding
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rle_packet = string.char(128 + count - 1, previous_b, previous_g, previous_r)
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packets[#packets +1] = rle_packet
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end
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end
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count = 1
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previous_r = pixel[1]
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previous_g = pixel[2]
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previous_b = pixel[3]
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else
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count = count + 1
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end
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end
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end
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if 1 == count then
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raw_pixel = string.char(previous_b, previous_g, previous_r)
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raw_pixels[#raw_pixels + 1] = raw_pixel
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raw_packet = string.char(#raw_pixels - 1)
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packets[#packets + 1] = raw_packet
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for i=1, #raw_pixels do
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packets[#packets +1] = raw_pixels[i]
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end
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raw_pixels = {}
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else
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-- encode raw pixels, if any
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if #raw_pixels > 0 then
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raw_packet = string.char(#raw_pixels - 1)
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packets[#packets + 1] = raw_packet
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for i=1, #raw_pixels do
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packets[#packets +1] = raw_pixels[i]
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end
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raw_pixels = {}
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end
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-- RLE encoding
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rle_packet = string.char(128 + count - 1, previous_b, previous_g, previous_r)
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packets[#packets +1] = rle_packet
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end
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self.data = self.data .. table.concat(packets)
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end
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function image:encode_footer()
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self.data = self.data
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.. string.char(0, 0, 0, 0) -- extension area offset
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.. string.char(0, 0, 0, 0) -- developer area offset
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.. "TRUEVISION-XFILE"
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.. "."
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.. string.char(0)
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end
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function image:encode(properties)
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self.data = ""
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self:encode_header(properties) -- header
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-- no color map and image id data
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self:encode_data(properties) -- encode data
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-- no extension or developer area
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self:encode_footer() -- footer
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end
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function image:save(filename, properties)
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local properties = properties or {}
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properties.colors = properties.colors or "RGB"
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properties.pixel_depth = properties.pixel_depth or 16
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self:encode(properties)
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local f = assert(io.open(filename, "wb"))
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f:write(self.data)
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f:close()
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end
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tga_encoder.image = image
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