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Allow encoding RGB images as B8G8R8
This commit is contained in:
Nils Dagsson Moskopp
parent
1b48c3f539
commit
9af0719df8
2 changed files with 103 additions and 11 deletions
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@ -46,4 +46,5 @@ for x = 1,16,1 do -- left to right
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pixels[z][x] = color
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end
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end
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tga_encoder.image(pixels):save("gradients.tga")
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tga_encoder.image(pixels, {pixel_depth=16}):save("gradients_16bpp.tga")
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tga_encoder.image(pixels, {pixel_depth=24}):save("gradients_24bpp.tga")
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111
init.lua
111
init.lua
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@ -8,13 +8,16 @@ local image = setmetatable({}, {
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end,
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})
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function image:constructor(pixels)
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function image:constructor(pixels, properties)
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local properties = properties or {}
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local pixel_depth = properties.pixel_depth or 16
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self.data = ""
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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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self:encode()
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self:encode(pixel_depth)
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end
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function image:encode_colormap_spec()
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@ -24,26 +27,38 @@ function image:encode_colormap_spec()
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.. string.char(0) -- bits per pixel
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end
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function image:encode_image_spec()
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function image:encode_image_spec(pixel_depth)
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assert(
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16 == pixel_depth or -- (A1R5G5B5 = 2 bytes = 16 bits)
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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(16) -- pixel depth (ARRRRRGGGGGBBBBB = 2 bytes = 16 bits)
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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()
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function image:encode_header(pixel_depth)
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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(10) -- image type (RLE RGB = 10)
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self:encode_colormap_spec() -- color map specification
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self:encode_image_spec() -- image specification
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self:encode_image_spec(pixel_depth) -- image specification
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end
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function image:encode_data()
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function image:encode_data(pixel_depth)
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if 16 == pixel_depth then
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self:encode_data_a1r5g5b5_rle()
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elseif 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_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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@ -132,6 +147,82 @@ function image:encode_data()
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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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@ -141,10 +232,10 @@ function image:encode_footer()
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.. string.char(0)
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end
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function image:encode()
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self:encode_header() -- header
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function image:encode(pixel_depth)
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self:encode_header(pixel_depth) -- header
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-- no color map and image id data
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self:encode_data() -- encode data
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self:encode_data(pixel_depth) -- 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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