From 1744376626e5ac3ee943520ba6e6863b479bc6bf Mon Sep 17 00:00:00 2001
From: John Firebaugh <john.firebaugh@gmail.com>
Date: Tue, 5 Dec 2017 09:34:08 -0800
Subject: [PATCH] Interpolate HCL with shortest path

---
 src/style-spec/util/color_spaces.js           |  23 +++++++++++-------
 .../colorSpace-hcl/expected.png               | Bin 192 -> 192 bytes
 2 files changed, 14 insertions(+), 9 deletions(-)

diff --git a/src/style-spec/util/color_spaces.js b/src/style-spec/util/color_spaces.js
index 9bab1886e40..3578d6fb151 100644
--- a/src/style-spec/util/color_spaces.js
+++ b/src/style-spec/util/color_spaces.js
@@ -1,7 +1,7 @@
 // @flow
 
 const Color = require('./color');
-const interpolate = require('./interpolate');
+const interpolateNumber = require('./interpolate').number;
 
 type LABColor = {
     l: number,
@@ -80,10 +80,10 @@ function labToRgb(labColor: LABColor): Color {
 
 function interpolateLab(from: LABColor, to: LABColor, t: number) {
     return {
-        l: interpolate.number(from.l, to.l, t),
-        a: interpolate.number(from.a, to.a, t),
-        b: interpolate.number(from.b, to.b, t),
-        alpha: interpolate.number(from.alpha, to.alpha, t)
+        l: interpolateNumber(from.l, to.l, t),
+        a: interpolateNumber(from.a, to.a, t),
+        b: interpolateNumber(from.b, to.b, t),
+        alpha: interpolateNumber(from.alpha, to.alpha, t)
     };
 }
 
@@ -111,12 +111,17 @@ function hclToRgb(hclColor: HCLColor): Color {
     });
 }
 
+function interpolateHue(a: number, b: number, t: number) {
+    const d = b - a;
+    return a + t * (d > 180 || d < -180 ? d - 360 * Math.round(d / 360) : d);
+}
+
 function interpolateHcl(from: HCLColor, to: HCLColor, t: number) {
     return {
-        h: interpolate.number(from.h, to.h, t),
-        c: interpolate.number(from.c, to.c, t),
-        l: interpolate.number(from.l, to.l, t),
-        alpha: interpolate.number(from.alpha, to.alpha, t)
+        h: interpolateHue(from.h, to.h, t),
+        c: interpolateNumber(from.c, to.c, t),
+        l: interpolateNumber(from.l, to.l, t),
+        alpha: interpolateNumber(from.alpha, to.alpha, t)
     };
 }
 
diff --git a/test/integration/render-tests/background-color/colorSpace-hcl/expected.png b/test/integration/render-tests/background-color/colorSpace-hcl/expected.png
index dbbd760d819402b1681e540ab0d4795505b5828b..3ef07516e2a03b88ad013a964dd1929160bf90f7 100644
GIT binary patch
literal 192
zcmeAS@N?(olHy`uVBq!ia0vp^4j|0I1|(Ny7TyC=Or9=|Ar*{or0OmKd6gjE(}RqR
x3<ewx1}dkO_tcy69y0rVUr4P`NS%g=J##hFwXaSdyMT^h@O1TaS?83{1OOHWFRB0l

literal 192
zcmeAS@N?(olHy`uVBq!ia0vp^4j|0I1|(Ny7TyC=Or9=|Ar*{or0OmKd6gjE(}RYL
x3<f+625tXW3#Dxlb^0`8e~agwBQ!*J80YIUZRYRazyx#zgQu&X%Q~loCIAbgPXGV_