From eabf6032a24a63a2341a2ca054300600e24c2868 Mon Sep 17 00:00:00 2001
From: "Adam D. Ruppe" <destructionator@gmail.com>
Date: Thu, 21 Jan 2021 10:22:10 -0500
Subject: [PATCH] fix from ketmar

---
 png.d | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/png.d b/png.d
index 909d89d..f42a127 100644
--- a/png.d
+++ b/png.d
@@ -1913,7 +1913,7 @@ immutable(ubyte)[] unfilter(ubyte filterType, in ubyte[] data, in ubyte[] previo
 			foreach(i; 0 .. arr.length) {
 				auto prev = i < bpp ? 0 : arr[i - bpp];
 				arr[i] += cast(ubyte)
-					/*std.math.floor*/( cast(int) (prev + previousLine[i]) / 2);
+					/*std.math.floor*/( cast(int) (prev + (previousLine.length ? previousLine[i] : 0)) / 2);
 			}
 
 			return assumeUnique(arr);