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Allow encoding RGB images as B8G8R8

This commit is contained in:
Nils Dagsson Moskopp 2022-05-14 20:44:12 +02:00
parent 1b48c3f539
commit 9af0719df8
Signed by untrusted user who does not match committer: erlehmann
GPG Key ID: A3BC671C35191080
2 changed files with 103 additions and 11 deletions

View File

@ -46,4 +46,5 @@ for x = 1,16,1 do -- left to right
pixels[z][x] = color
end
end
tga_encoder.image(pixels):save("gradients.tga")
tga_encoder.image(pixels, {pixel_depth=16}):save("gradients_16bpp.tga")
tga_encoder.image(pixels, {pixel_depth=24}):save("gradients_24bpp.tga")

111
init.lua
View File

@ -8,13 +8,16 @@ local image = setmetatable({}, {
end,
})
function image:constructor(pixels)
function image:constructor(pixels, properties)
local properties = properties or {}
local pixel_depth = properties.pixel_depth or 16
self.data = ""
self.pixels = pixels
self.width = #pixels[1]
self.height = #pixels
self:encode()
self:encode(pixel_depth)
end
function image:encode_colormap_spec()
@ -24,26 +27,38 @@ function image:encode_colormap_spec()
.. string.char(0) -- bits per pixel
end
function image:encode_image_spec()
function image:encode_image_spec(pixel_depth)
assert(
16 == pixel_depth or -- (A1R5G5B5 = 2 bytes = 16 bits)
24 == pixel_depth -- (B8G8R8 = 3 bytes = 24 bits)
)
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(16) -- pixel depth (ARRRRRGGGGGBBBBB = 2 bytes = 16 bits)
.. string.char(pixel_depth)
.. string.char(0) -- image descriptor
end
function image:encode_header()
function image:encode_header(pixel_depth)
self.data = self.data
.. string.char(0) -- image id
.. string.char(0) -- color map type
.. string.char(10) -- image type (RLE RGB = 10)
self:encode_colormap_spec() -- color map specification
self:encode_image_spec() -- image specification
self:encode_image_spec(pixel_depth) -- image specification
end
function image:encode_data()
function image:encode_data(pixel_depth)
if 16 == pixel_depth then
self:encode_data_a1r5g5b5_rle()
elseif 24 == pixel_depth then
self:encode_data_r8g8b8_rle()
end
end
function image:encode_data_a1r5g5b5_rle()
local colorword = nil
local previous_r = nil
local previous_g = nil
@ -132,6 +147,82 @@ function image:encode_data()
self.data = self.data .. table.concat(packets)
end
function image:encode_data_r8g8b8_rle()
local previous_r = nil
local previous_g = nil
local previous_b = 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 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)
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)
packets[#packets +1] = rle_packet
end
end
count = 1
previous_r = pixel[1]
previous_g = pixel[2]
previous_b = pixel[3]
else
count = count + 1
end
end
end
if 1 == count then
raw_pixel = string.char(previous_b, previous_g, previous_r)
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)
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
@ -141,10 +232,10 @@ function image:encode_footer()
.. string.char(0)
end
function image:encode()
self:encode_header() -- header
function image:encode(pixel_depth)
self:encode_header(pixel_depth) -- header
-- no color map and image id data
self:encode_data() -- encode data
self:encode_data(pixel_depth) -- encode data
-- no extension or developer area
self:encode_footer() -- footer
end