Add a simple PNG image encoder with Lua API (#11485)

* Add a simple PNG image encoder with Lua API
Add ColorSpec to RGBA converter
Make a safety wrapper for the encoder
Create devtest examples

Co-authored-by: hecktest <>
Co-authored-by: sfan5 <sfan5@live.de>

1 files changed, 39 insertions, 0 deletions

diff --git a/builtin/game/misc.lua b/builtin/game/misc.lua
index c13a583f0..cee95dd23 100644
--- a/builtin/game/misc.lua
+++ b/builtin/game/misc.lua
@@ -290,3 +290,42 @@ function core.dynamic_add_media(filepath, callback)
 	end
 	return true
 end
+
+
+-- PNG encoder safety wrapper
+
+local o_encode_png = core.encode_png
+function core.encode_png(width, height, data, compression)
+	if type(width) ~= "number" then
+		error("Incorrect type for 'width', expected number, got " .. type(width))
+	end
+	if type(height) ~= "number" then
+		error("Incorrect type for 'height', expected number, got " .. type(height))
+	end
+
+	local expected_byte_count = width * height * 4;
+
+	if type(data) ~= "table" and type(data) ~= "string" then
+		error("Incorrect type for 'height', expected table or string, got " .. type(height));
+	end
+
+	local data_length = type(data) == "table" and #data * 4 or string.len(data);
+
+	if data_length ~= expected_byte_count then
+		error(string.format(
+			"Incorrect length of 'data', width and height imply %d bytes but %d were provided",
+			expected_byte_count,
+			data_length
+		))
+	end
+
+	if type(data) == "table" then
+		local dataBuf = {}
+		for i = 1, #data do
+			dataBuf[i] = core.colorspec_to_bytes(data[i])
+		end
+		data = table.concat(dataBuf)
+	end
+
+	return o_encode_png(width, height, data, compression or 6)
+end