+ Initial Import

This is the code from <https://github.com/minetest/minetest/pull/13955>.

init.lua

@@ -0,0 +1,88 @@
+--[[
+
+The following nodes are monochrome checkerboard nodes.
+Their textures have odd sizes that are sometimes used,
+e.g. in texture packs that use other sizes than 16×16.
+
+Those nodes are useful to see how textures are scaled:
+You may be able to find rendering bugs with the nodes,
+e.g. artifacts when scaling non-power-of-two textures.
+
+The choice of uncompressed monochrome TGAs is for debugging –
+it is easy to understand the generated images with a hexdump.
+(If you have never done that, it is not your place to judge.)
+
+]]--
+
+
+function encode_tga_type_3(w, h, ...)
+	assert((w <= 256) and (h <= 256) and (w * h == #{...}))
+	local bytes = string.char
+	local header = bytes(0, 0, 3, 0, 0, 0, 0, 0, 0, 0, 0, 0, w, 0, h, 0, 8, 0)
+	local footer = bytes(0, 0, 0, 0, 0, 0, 0, 0) .. "TRUEVISION-XFILE." .. bytes(0)
+	return(header .. bytes(...) .. footer)
+end
+
+function generate_checkerboard(width, height, wtile, htile)
+	local pixels = {}
+	for h = 1,height do
+		for w = 1,width do
+			local hori = math.floor((w - 1) / wtile) % 2 == 0
+			local vert = math.floor((h - 1) / htile) % 2 == 0
+			-- off-white & off-black to stand out in hexdump
+			local color = hori ~= vert and 0xEE or 0x11
+			if (
+				0 == math.floor((w - 1) / wtile) and
+				0 == math.floor((h - 1) / htile)
+			) then
+				color = "0x7F"
+			end
+			pixels[#pixels + 1] = color
+		end
+	end
+	return pixels
+end
+
+function generate_checkerboard_node(width, height, wtiles, htiles)
+	local id = "cb_bw_" ..
+		wtiles .. "x" .. htiles .. "_" ..
+		width .. "x" .. height
+	local filename = id .. ".tga"
+	local pixels = generate_checkerboard(
+		width, height,
+		math.floor(width/wtiles), math.floor(height/htiles)
+	)
+	minetest.safe_file_write(
+		textures_path .. filename,
+		encode_tga_type_3(width, height, unpack(pixels))
+	)
+	local nodename = "testnodes:" .. id
+	minetest.register_node(nodename, {
+		description = S(
+			"Checkerboard Test Node " ..
+			"(Tiling: " .. wtiles .. "×" .. htiles .. ") " ..
+			width .. "×" .. height ..
+			"\nNodes with same tiling should look alike."
+		),
+		groups = { dig_immediate = 2 },
+		tiles = { filename },
+	})
+end
+
+-- multiples of 2
+for i = 2,16,2 do generate_checkerboard_node(i, i, 2, 2) end
+
+-- multiples of 3
+for i = 3,9,3 do generate_checkerboard_node(i, i, 3, 3) end
+
+-- multiples of 4
+for i = 4,16,4 do generate_checkerboard_node(i, i, 4, 4) end
+
+-- multiples of 5
+for i = 5,15,5 do generate_checkerboard_node(i, i, 5, 5) end
+
+-- multiples of 7
+for i = 7,21,7 do generate_checkerboard_node(i, i, 7, 7) end
+
+-- multiples of 16
+for i = 16,64,16 do generate_checkerboard_node(i, i, 16, 16) end