Allow encoding with B8G8R8A8 colormap

README.md

@@ -59,6 +59,7 @@ These images contain a palette, followed by pixel data.
 
 * `A1R5G5B5` (8bpp RGB)
 * `B8G8R8` (8bpp RGB)
+* `B8G8R8A8` (8bpp RGBA)
 
 ### True-Color Images (Type 2)
 
@@ -82,6 +83,5 @@ These images contain compressed RGB(A) pixel data.
 
 ## TODO
 
-* Support Type 1 `B8G8R8A8` output (color-mapped 8bpp RGBA)
 * Actually support `R8G8B8A8` input for `A1R5G5B5` output
 * Add both zoomable and explorable maps to `mcl_maps`.

examples.lua

@@ -128,3 +128,23 @@ local pixels = {
 tga_encoder.image(pixels):save("colormapped_B8G8R8.tga", {colormap=colormap})
 -- encoding as A1R5G5B5 saves 1 byte per palette entry → 103 bytes
 tga_encoder.image(pixels):save("colormapped_A1R5G5B5.tga", {colormap=colormap, color_format="A1R5G5B5"})
+
+-- encode a colormapped bitmap with transparency
+local _ = { 0 }
+local K = { 1 }
+local W = { 2 }
+local colormap = {
+	{   0,   0,   0,   0 },
+	{   0,   0,   0, 255 },
+	{ 255, 255, 255, 255 },
+}
+local pixels = {
+	{ _, K, K, K, K, K, _ },
+	{ _, K, W, W, W, K, _ },
+	{ K, K, W, W, W, K, K },
+	{ K, W, W, W, W, W, K },
+	{ _, K, W, W, W, K, _ },
+	{ _, _, K, W, K, _, _ },
+	{ _, _, _, K, _, _, _ },
+}
+tga_encoder.image(pixels):save("colormapped_B8G8R8A8.tga", {colormap=colormap})

init.lua

@@ -68,7 +68,8 @@ function image:encode_colormap(properties)
 	local color_format = properties.color_format
 	assert (
 		"A1R5G5B5" == color_format or
-		"B8G8R8" == color_format
+		"B8G8R8" == color_format or
+		"B8G8R8A8" == color_format
 	)
 	local colors = {}
 	if "A1R5G5B5" == color_format then
@@ -98,6 +99,17 @@ function image:encode_colormap(properties)
 			)
 			colors[#colors + 1] = color_bytes
 		end
+	elseif "B8G8R8A8" == color_format then
+		for i = 1,#colormap,1 do
+			local color = colormap[i]
+			local color_bytes = string.char(
+				color[3], -- B
+				color[2], -- G
+				color[1], -- R
+				color[4]  -- A
+			)
+			colors[#colors + 1] = color_bytes
+		end
 	end
 	assert( 0 ~= #colors )
 	self.data = self.data .. table.concat(colors)
@@ -182,12 +194,20 @@ function image:encode_data(properties)
 			end
 		end
 	elseif "B8G8R8A8" == color_format then
+		if 0 ~= #colormap then
+			if "RAW" == compression then
+				if 8 == self.pixel_depth then
+					self:encode_data_Y8_as_Y8_raw()
+				end
+			end
+		else
 			if "RAW" == compression then
 				self:encode_data_R8G8B8A8_as_B8G8R8A8_raw()
 			elseif "RLE" == compression then
 				self:encode_data_R8G8B8A8_as_B8G8R8A8_rle()
 			end
 		end
+	end
 	local data_length_after = #self.data
 	assert(
 		data_length_after ~= data_length_before,