629 lines
18 KiB
Lua
629 lines
18 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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local pixel_depth_by_color_format = {
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["Y8"] = 8,
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["A1R5G5B5"] = 16,
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["B8G8R8"] = 24,
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["B8G8R8A8"] = 32,
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}
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function image:encode_colormap_spec(properties)
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local colormap = properties.colormap
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local colormap_pixel_depth = 0
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if 0 ~= #colormap then
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colormap_pixel_depth = pixel_depth_by_color_format[
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properties.color_format
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]
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-- ensure that each pixel references a legal colormap entry
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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 colormap_index = pixel[1]
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if colormap_index >= #colormap then
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error(
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"colormap index " .. colormap_index ..
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" not in colormap of size " .. #colormap
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)
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end
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end
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end
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end
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local colormap_spec =
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string.char(0, 0) .. -- first entry index
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string.char(#colormap % 256, math.floor(#colormap / 256)) .. -- number of entries
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string.char(colormap_pixel_depth) -- bits per pixel
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self.data = self.data .. colormap_spec
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end
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function image:encode_image_spec(properties)
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local color_format = properties.color_format
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assert(
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"Y8" == color_format or -- (8 bit grayscale = 1 byte = 8 bits)
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"A1R5G5B5" == color_format or -- (A1R5G5B5 = 2 bytes = 16 bits)
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"B8G8R8" == color_format or -- (B8G8R8 = 3 bytes = 24 bits)
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"B8G8R8A8" == color_format -- (B8G8R8A8 = 4 bytes = 32 bits)
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)
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local scanline_order = properties.scanline_order
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assert (
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"bottom-top" == scanline_order or
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"top-bottom" == scanline_order
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)
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local pixel_depth
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if 0 ~= #properties.colormap then
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pixel_depth = self.pixel_depth
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else
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pixel_depth = pixel_depth_by_color_format[color_format]
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end
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assert( nil ~= pixel_depth)
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-- the origin is the bottom left corner of the image (always)
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local x_origin_lo = 0
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local x_origin_hi = 0
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local y_origin_lo = 0
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local y_origin_hi = 0
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local image_descriptor = 0 -- equal to bottom-top scanline order
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local width_lo = self.width % 256
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local width_hi = math.floor(self.width / 256)
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local height_lo = self.height % 256
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local height_hi = math.floor(self.height / 256)
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if "top-bottom" == scanline_order then
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image_descriptor = 32
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y_origin_lo = height_lo
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y_origin_hi = height_hi
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end
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self.data = self.data .. string.char (
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x_origin_lo, x_origin_hi,
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y_origin_lo, y_origin_hi,
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width_lo, width_hi,
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height_lo, height_hi,
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pixel_depth,
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image_descriptor
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)
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end
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function image:encode_colormap(properties)
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local colormap = properties.colormap
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if 0 == #colormap then
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return
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end
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local color_format = properties.color_format
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assert (
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"A1R5G5B5" == color_format or
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"B8G8R8" == color_format or
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"B8G8R8A8" == color_format
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)
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local colors = {}
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if "A1R5G5B5" == color_format then
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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 i = 1,#colormap,1 do
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local color = colormap[i]
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local colorword = 32768 +
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((math.floor((color[1] * max_sample_out / max_sample_in) + 0.5)) * 1024) +
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((math.floor((color[2] * max_sample_out / max_sample_in) + 0.5)) * 32) +
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((math.floor((color[3] * max_sample_out / max_sample_in) + 0.5)) * 1)
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local color_bytes = string.char(
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colorword % 256,
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math.floor(colorword / 256)
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)
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colors[#colors + 1] = color_bytes
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end
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elseif "B8G8R8" == color_format then
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for i = 1,#colormap,1 do
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local color = colormap[i]
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local color_bytes = string.char(
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color[3], -- B
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color[2], -- G
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color[1] -- R
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)
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colors[#colors + 1] = color_bytes
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end
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elseif "B8G8R8A8" == color_format then
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for i = 1,#colormap,1 do
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local color = colormap[i]
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local color_bytes = string.char(
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color[3], -- B
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color[2], -- G
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color[1], -- R
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color[4] -- A
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)
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colors[#colors + 1] = color_bytes
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end
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end
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assert( 0 ~= #colors )
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self.data = self.data .. table.concat(colors)
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end
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function image:encode_header(properties)
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local color_format = properties.color_format
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local colormap = properties.colormap
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local compression = properties.compression
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local colormap_type
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local image_type
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if "Y8" == color_format and "RAW" == compression then
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colormap_type = 0
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image_type = 3 -- grayscale
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elseif (
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"A1R5G5B5" == color_format or
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"B8G8R8" == color_format or
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"B8G8R8A8" == color_format
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) then
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if "RAW" == compression then
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if 0 ~= #colormap then
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colormap_type = 1
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image_type = 1 -- colormapped RGB(A)
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else
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colormap_type = 0
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image_type = 2 -- RAW RGB(A)
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end
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elseif "RLE" == compression then
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colormap_type = 0
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image_type = 10 -- RLE RGB
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end
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end
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assert( nil ~= colormap_type )
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assert( nil ~= image_type )
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self.data = self.data
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.. string.char(0) -- image id
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.. string.char(colormap_type)
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.. string.char(image_type)
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self:encode_colormap_spec(properties) -- color map specification
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self:encode_image_spec(properties) -- image specification
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self:encode_colormap(properties)
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end
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function image:encode_data(properties)
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local color_format = properties.color_format
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local colormap = properties.colormap
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local compression = properties.compression
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local data_length_before = #self.data
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if "Y8" == color_format and "RAW" == compression then
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if 8 == self.pixel_depth then
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self:encode_data_Y8_as_Y8_raw()
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elseif 24 == self.pixel_depth then
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self:encode_data_R8G8B8_as_Y8_raw()
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end
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elseif "A1R5G5B5" == color_format then
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if 0 ~= #colormap then
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if "RAW" == compression then
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if 8 == self.pixel_depth then
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self:encode_data_Y8_as_Y8_raw()
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end
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end
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else
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if "RAW" == compression then
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self:encode_data_R8G8B8_as_A1R5G5B5_raw()
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elseif "RLE" == compression then
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self:encode_data_R8G8B8_as_A1R5G5B5_rle()
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end
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end
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elseif "B8G8R8" == color_format then
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if 0 ~= #colormap then
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if "RAW" == compression then
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if 8 == self.pixel_depth then
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self:encode_data_Y8_as_Y8_raw()
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end
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end
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else
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if "RAW" == compression then
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self:encode_data_R8G8B8_as_B8G8R8_raw()
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elseif "RLE" == compression then
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self:encode_data_R8G8B8_as_B8G8R8_rle()
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end
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end
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elseif "B8G8R8A8" == color_format then
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if 0 ~= #colormap then
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if "RAW" == compression then
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if 8 == self.pixel_depth then
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self:encode_data_Y8_as_Y8_raw()
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end
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end
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else
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if "RAW" == compression then
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self:encode_data_R8G8B8A8_as_B8G8R8A8_raw()
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elseif "RLE" == compression then
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self:encode_data_R8G8B8A8_as_B8G8R8A8_rle()
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end
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end
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end
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local data_length_after = #self.data
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assert(
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data_length_after ~= data_length_before,
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"No data encoded for color format: " .. color_format
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)
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end
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function image:encode_data_Y8_as_Y8_raw()
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assert(8 == self.pixel_depth)
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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_R8G8B8_as_Y8_raw()
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assert(24 == self.pixel_depth)
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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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-- the HSP RGB to brightness formula is
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-- sqrt( 0.299 r² + .587 g² + .114 b² )
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-- see <https://alienryderflex.com/hsp.html>
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local gray = math.floor(
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math.sqrt(
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0.299 * pixel[1]^2 +
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0.587 * pixel[2]^2 +
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0.114 * pixel[3]^2
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) + 0.5
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)
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local raw_pixel = string.char(gray)
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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_R8G8B8_as_A1R5G5B5_raw()
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assert(24 == self.pixel_depth)
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local raw_pixels = {}
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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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local colorword = 32768 +
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((math.floor((pixel[1] * max_sample_out / max_sample_in) + 0.5)) * 1024) +
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((math.floor((pixel[2] * max_sample_out / max_sample_in) + 0.5)) * 32) +
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((math.floor((pixel[3] * max_sample_out / max_sample_in) + 0.5)) * 1)
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local 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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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_R8G8B8_as_A1R5G5B5_rle()
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assert(24 == self.pixel_depth)
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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_as_B8G8R8_raw()
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assert(24 == self.pixel_depth)
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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[3], pixel[2], 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_R8G8B8_as_B8G8R8_rle()
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assert(24 == self.pixel_depth)
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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
|
|
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]
|
|
previous_b = pixel[3]
|
|
else
|
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count = count + 1
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end
|
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end
|
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end
|
|
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
|
|
raw_pixels = {}
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else
|
|
-- encode raw pixels, if any
|
|
if #raw_pixels > 0 then
|
|
raw_packet = string.char(#raw_pixels - 1)
|
|
packets[#packets + 1] = raw_packet
|
|
for i=1, #raw_pixels do
|
|
packets[#packets +1] = raw_pixels[i]
|
|
end
|
|
raw_pixels = {}
|
|
end
|
|
-- RLE encoding
|
|
rle_packet = string.char(128 + count - 1, previous_b, previous_g, previous_r)
|
|
packets[#packets +1] = rle_packet
|
|
end
|
|
self.data = self.data .. table.concat(packets)
|
|
end
|
|
|
|
function image:encode_data_R8G8B8A8_as_B8G8R8A8_raw()
|
|
assert(32 == self.pixel_depth)
|
|
local raw_pixels = {}
|
|
for _, row in ipairs(self.pixels) do
|
|
for _, pixel in ipairs(row) do
|
|
local raw_pixel = string.char(pixel[3], pixel[2], pixel[1], pixel[4])
|
|
raw_pixels[#raw_pixels + 1] = raw_pixel
|
|
end
|
|
end
|
|
self.data = self.data .. table.concat(raw_pixels)
|
|
end
|
|
|
|
function image:encode_data_R8G8B8A8_as_B8G8R8A8_rle()
|
|
assert(32 == self.pixel_depth)
|
|
local previous_r = nil
|
|
local previous_g = nil
|
|
local previous_b = nil
|
|
local previous_a = nil
|
|
local raw_pixel = ''
|
|
local raw_pixels = {}
|
|
local count = 1
|
|
local packets = {}
|
|
local raw_packet = ''
|
|
local rle_packet = ''
|
|
for _, row in ipairs(self.pixels) do
|
|
for _, pixel in ipairs(row) do
|
|
if pixel[1] ~= previous_r or pixel[2] ~= previous_g or pixel[3] ~= previous_b or pixel[4] ~= previous_a or count == 128 then
|
|
if nil ~= previous_r then
|
|
if 1 == count then
|
|
-- remember pixel verbatim for raw encoding
|
|
raw_pixel = string.char(previous_b, previous_g, previous_r, previous_a)
|
|
raw_pixels[#raw_pixels + 1] = raw_pixel
|
|
if 128 == #raw_pixels then
|
|
raw_packet = string.char(#raw_pixels - 1)
|
|
packets[#packets + 1] = raw_packet
|
|
for i=1, #raw_pixels do
|
|
packets[#packets +1] = raw_pixels[i]
|
|
end
|
|
raw_pixels = {}
|
|
end
|
|
else
|
|
-- encode raw pixels, if any
|
|
if #raw_pixels > 0 then
|
|
raw_packet = string.char(#raw_pixels - 1)
|
|
packets[#packets + 1] = raw_packet
|
|
for i=1, #raw_pixels do
|
|
packets[#packets +1] = raw_pixels[i]
|
|
end
|
|
raw_pixels = {}
|
|
end
|
|
-- RLE encoding
|
|
rle_packet = string.char(128 + count - 1, previous_b, previous_g, previous_r, previous_a)
|
|
packets[#packets +1] = rle_packet
|
|
end
|
|
end
|
|
count = 1
|
|
previous_r = pixel[1]
|
|
previous_g = pixel[2]
|
|
previous_b = pixel[3]
|
|
previous_a = pixel[4]
|
|
else
|
|
count = count + 1
|
|
end
|
|
end
|
|
end
|
|
if 1 == count then
|
|
raw_pixel = string.char(previous_b, previous_g, previous_r, previous_a)
|
|
raw_pixels[#raw_pixels + 1] = raw_pixel
|
|
raw_packet = string.char(#raw_pixels - 1)
|
|
packets[#packets + 1] = raw_packet
|
|
for i=1, #raw_pixels do
|
|
packets[#packets +1] = raw_pixels[i]
|
|
end
|
|
raw_pixels = {}
|
|
else
|
|
-- encode raw pixels, if any
|
|
if #raw_pixels > 0 then
|
|
raw_packet = string.char(#raw_pixels - 1)
|
|
packets[#packets + 1] = raw_packet
|
|
for i=1, #raw_pixels do
|
|
packets[#packets +1] = raw_pixels[i]
|
|
end
|
|
raw_pixels = {}
|
|
end
|
|
-- RLE encoding
|
|
rle_packet = string.char(128 + count - 1, previous_b, previous_g, previous_r, previous_a)
|
|
packets[#packets +1] = rle_packet
|
|
end
|
|
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(properties)
|
|
local properties = properties or {}
|
|
properties.colormap = properties.colormap or {}
|
|
properties.compression = properties.compression or "RAW"
|
|
properties.scanline_order = properties.scanline_order or "bottom-top"
|
|
|
|
self.pixel_depth = #self.pixels[1][1] * 8
|
|
|
|
local color_format_defaults_by_pixel_depth = {
|
|
[8] = "Y8",
|
|
[24] = "B8G8R8",
|
|
[32] = "B8G8R8A8",
|
|
}
|
|
if nil == properties.color_format then
|
|
if 0 ~= #properties.colormap then
|
|
properties.color_format =
|
|
color_format_defaults_by_pixel_depth[
|
|
#properties.colormap[1] * 8
|
|
]
|
|
else
|
|
properties.color_format =
|
|
color_format_defaults_by_pixel_depth[
|
|
self.pixel_depth
|
|
]
|
|
end
|
|
end
|
|
assert( nil ~= properties.color_format )
|
|
|
|
self.data = ""
|
|
self:encode_header(properties) -- header
|
|
-- no color map and image id data
|
|
self:encode_data(properties) -- encode data
|
|
-- no extension or developer area
|
|
self:encode_footer() -- footer
|
|
end
|
|
|
|
function image:save(filename, properties)
|
|
self:encode(properties)
|
|
|
|
local f = assert(io.open(filename, "wb"))
|
|
f:write(self.data)
|
|
f:close()
|
|
end
|
|
|
|
tga_encoder.image = image
|