Bugfix/faulty lch interpolation wrapping

CHANGELOG.md

@@ -3,9 +3,18 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/), and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
 
+## [v3.0.1] - 2021-08-06
+
+### Added
+- Start interpolation and wrapping test cases
+
+### Fixed
+- Faulty LCH interpolation wrapping [\#17](https://github.com/gurki/vivid/pull/17)
+
+
 ## [v3.0.0] - 2021-02-22
 
-## Added
+### Added
 - Add interpolation in `Linear RGB` for `Color`
 - Add convenience `Color::linearRgb()` getter
 - Add gamma correction section and example to README

src/interpolation.cpp

@@ -66,7 +66,7 @@ lch_t lerp( const lch_t& lch1, const lch_t& lch2, const float t )
     if ( delta.z > 180.f ) {
         delta.z -= 360.f;
     } else if ( delta.z < - 180.f ) {
-        delta.z += 380.f;
+        delta.z += 360.f;
     }
 
     auto interp = lch1 + t * delta;

tests/CMakeLists.txt

@@ -11,6 +11,7 @@ set( SOURCES
     test_main.cpp
     test_conversion_manual.cpp
     test_profiles.cpp
+    test_wrapping.cpp
 )
 
 set( DEPENDENCIES vivid )

tests/test_wrapping.cpp

@@ -0,0 +1,26 @@
+#include "utility.h"
+
+#include "vivid/interpolation.h"
+#include "vivid/conversion.h"
+#include "vivid/stream.h"
+
+#include "catch.hpp"
+
+
+////////////////////////////////////////////////////////////////////////////////
+TEST_CASE( "Wrapping", "[interpolation]" )
+{
+    using namespace vivid;
+
+    SECTION( "LCH" ) 
+    {
+        const lch_t colA { 10.f, 0.f, 10.f };
+        const lch_t colB { 40.f, 20.f, 200.f };
+
+        const lch_t colAB = lerp( colA, colB, 0.5f );
+        const lch_t colBA = lerp( colB, colA, 0.5f );
+
+        CAPTURE( colA, colB, colAB, colBA );
+        REQUIRE( colAB == colBA );
+    }
+}