From 25b7b30945241cb22529bb60fdb44248a64c19a6 Mon Sep 17 00:00:00 2001 From: Nils Dagsson Moskopp Date: Sat, 14 May 2022 22:41:52 +0200 Subject: [PATCH] Allow encoding grayscale images as BW8 --- examples.lua | 16 +++++++++++++-- init.lua | 58 +++++++++++++++++++++++++++++++++++++++------------- 2 files changed, 58 insertions(+), 16 deletions(-) diff --git a/examples.lua b/examples.lua index 5e16722f3..e21e4db95 100644 --- a/examples.lua +++ b/examples.lua @@ -29,6 +29,18 @@ for x = 1,56,1 do end tga_encoder.image(pixels):save("bitmap_large.tga") +-- note that the uncompressed grayscale TGA file written in this +-- example is 80 bytes – but an optimized PNG file is 81 bytes … +local pixels = {} +for x = 1,6,1 do -- left to right + for z = 1,6,1 do -- bottom to top + local color = { math.min(x * z * 4 - 1, 255) } + pixels[z] = pixels[z] or {} + pixels[z][x] = color + end +end +tga_encoder.image(pixels, {colors="BW", pixel_depth=8}):save("gradients_8bpp.tga") + local pixels = {} for x = 1,16,1 do -- left to right for z = 1,16,1 do -- bottom to top @@ -46,5 +58,5 @@ for x = 1,16,1 do -- left to right pixels[z][x] = color end end -tga_encoder.image(pixels, {pixel_depth=16}):save("gradients_16bpp.tga") -tga_encoder.image(pixels, {pixel_depth=24}):save("gradients_24bpp.tga") +tga_encoder.image(pixels, {colors="RGB", pixel_depth=16}):save("gradients_16bpp.tga") +tga_encoder.image(pixels, {colors="RGB", pixel_depth=24}):save("gradients_24bpp.tga") diff --git a/init.lua b/init.lua index d8a044244..aad7f2cac 100644 --- a/init.lua +++ b/init.lua @@ -10,14 +10,15 @@ local image = setmetatable({}, { function image:constructor(pixels, properties) local properties = properties or {} - local pixel_depth = properties.pixel_depth or 16 + properties.colors = properties.colors or "RGB" + properties.pixel_depth = properties.pixel_depth or 16 self.data = "" self.pixels = pixels self.width = #pixels[1] self.height = #pixels - self:encode(pixel_depth) + self:encode(properties) end function image:encode_colormap_spec() @@ -27,10 +28,13 @@ function image:encode_colormap_spec() .. string.char(0) -- bits per pixel end -function image:encode_image_spec(pixel_depth) +function image:encode_image_spec(properties) + local colors = properties.colors + local pixel_depth = properties.pixel_depth assert( - 16 == pixel_depth or -- (A1R5G5B5 = 2 bytes = 16 bits) - 24 == pixel_depth -- (B8G8R8 = 3 bytes = 24 bits) + "BW" == colors and 8 == pixel_depth or -- (8 bit grayscale = 1 byte = 8 bits) + "RGB" == colors and 16 == pixel_depth or -- (A1R5G5B5 = 2 bytes = 16 bits) + "RGB" == colors and 24 == pixel_depth -- (B8G8R8 = 3 bytes = 24 bits) ) self.data = self.data .. string.char(0, 0) -- X-origin @@ -41,23 +45,49 @@ function image:encode_image_spec(pixel_depth) .. string.char(0) -- image descriptor end -function image:encode_header(pixel_depth) +function image:encode_header(properties) + local colors = properties.colors + local pixel_depth = properties.pixel_depth + local image_type + if "BW" == colors and 8 == pixel_depth then + image_type = 3 -- grayscale + elseif ( + "RGB" == colors and 16 == pixel_depth or + "RGB" == colors and 24 == pixel_depth + ) then + image_type = 10 -- RLE RGB + end self.data = self.data .. string.char(0) -- image id .. string.char(0) -- color map type - .. string.char(10) -- image type (RLE RGB = 10) + .. string.char(image_type) self:encode_colormap_spec() -- color map specification - self:encode_image_spec(pixel_depth) -- image specification + self:encode_image_spec(properties) -- image specification end -function image:encode_data(pixel_depth) - if 16 == pixel_depth then +function image:encode_data(properties) + local colors = properties.colors + local pixel_depth = properties.pixel_depth + if "BW" == colors and 8 == pixel_depth then + self:encode_data_bw8() + elseif "RGB" == colors and 16 == pixel_depth then self:encode_data_a1r5g5b5_rle() - elseif 24 == pixel_depth then + elseif "RGB" == colors and 24 == pixel_depth then self:encode_data_r8g8b8_rle() end end +function image:encode_data_bw8() + local raw_pixels = {} + for _, row in ipairs(self.pixels) do + for _, pixel in ipairs(row) do + local raw_pixel = string.char(pixel[1]) + raw_pixels[#raw_pixels + 1] = raw_pixel + end + end + self.data = self.data .. table.concat(raw_pixels) +end + function image:encode_data_a1r5g5b5_rle() local colorword = nil local previous_r = nil @@ -232,10 +262,10 @@ function image:encode_footer() .. string.char(0) end -function image:encode(pixel_depth) - self:encode_header(pixel_depth) -- header +function image:encode(properties) + self:encode_header(properties) -- header -- no color map and image id data - self:encode_data(pixel_depth) -- encode data + self:encode_data(properties) -- encode data -- no extension or developer area self:encode_footer() -- footer end