From eab5bd744ff23fa92e456f62f0ce9a19e27f1f1f Mon Sep 17 00:00:00 2001
From: Jochen Derwae <jochen.derwae@gmail.com>
Date: Tue, 12 Nov 2019 20:10:23 +0100
Subject: [PATCH] Added fill style for transparent background (erase buffer to
 full transparency)

---
 index.html | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/index.html b/index.html
index 74b970e..fd73a99 100644
--- a/index.html
+++ b/index.html
@@ -696,14 +696,18 @@
 			//canvas.height = settings["screenHeight"];
 
 			// Invert background if needed
-			if (settings["backgroundColor"] != "transparent") {
+			if (settings["backgroundColor"] == "transparent") {
+				ctx.fillStyle = "rgba(0,0,0,0.0)";
+				ctx.globalCompositeOperation = 'copy';
+			} else {
 				if (settings["invertColors"]){
 					settings["backgroundColor"] == "white" ? ctx.fillStyle = "black" : ctx.fillStyle = "white";
-				}else{
+				} else {
 					ctx.fillStyle = settings["backgroundColor"];
 				}
-				ctx.fillRect(0, 0, canvas.width, canvas.height);
+				ctx.globalCompositeOperation = 'source-over';
 			}
+			ctx.fillRect(0, 0, canvas.width, canvas.height);
 
 			// Offset used for centering the image when requested
 			var offset_x = 0;