From 9af0719df8dc5895633e5ce2ee107f78eb7a1bd0 Mon Sep 17 00:00:00 2001 From: Nils Dagsson Moskopp Date: Sat, 14 May 2022 20:44:12 +0200 Subject: [PATCH] Allow encoding RGB images as B8G8R8 --- examples.lua | 3 +- init.lua | 111 ++++++++++++++++++++++++++++++++++++++++++++++----- 2 files changed, 103 insertions(+), 11 deletions(-) diff --git a/examples.lua b/examples.lua index b832dddaa..5e16722f3 100644 --- a/examples.lua +++ b/examples.lua @@ -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") diff --git a/init.lua b/init.lua index a6972843e..d8a044244 100644 --- a/init.lua +++ b/init.lua @@ -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