From 6a77ba51ddc8ed95177fb16b82d8275c88f35349 Mon Sep 17 00:00:00 2001
From: Dirk Stolle <striezel-dev@web.de>
Date: Mon, 25 Apr 2022 19:47:56 +0200
Subject: [PATCH] fix is_equal_to_sixteen in PNG I/O extension

While is_equal_to_sixteen should (as the name suggests) check for
equality to 16, it actually checked whether the bit depth was
less than 16.
---
 .../gil/extension/io/png/detail/write.hpp     | 20 ++++++++++++++++---
 1 file changed, 17 insertions(+), 3 deletions(-)

diff --git a/include/boost/gil/extension/io/png/detail/write.hpp b/include/boost/gil/extension/io/png/detail/write.hpp
index eee5b9ed1c..02c5422e68 100644
--- a/include/boost/gil/extension/io/png/detail/write.hpp
+++ b/include/boost/gil/extension/io/png/detail/write.hpp
@@ -171,10 +171,24 @@ class writer< Device
     {};
 
     template<typename Info>
-    struct is_equal_to_sixteen : mp11::mp_less
+    struct is_equal_to_sixteen : mp11::mp_and
         <
-            std::integral_constant<int, Info::_bit_depth>,
-            std::integral_constant<int, 16>
+            mp11::mp_not
+            <
+                mp11::mp_less
+                <
+                    std::integral_constant<int, Info::_bit_depth>,
+                    std::integral_constant<int, 16>
+                >
+            >,
+            mp11::mp_not
+            <
+                mp11::mp_less
+                <
+                    std::integral_constant<int, 16>,
+                    std::integral_constant<int, Info::_bit_depth>
+                >
+            >
         >
     {};