From cfabc92945589b50c87b127d1bc688b3cd1af43d Mon Sep 17 00:00:00 2001
From: Jeremy Ruston <jeremy@jermolene.com>
Date: Sat, 16 Nov 2024 14:37:14 +0000
Subject: [PATCH] Update contrastcolour macro to use color.js

---
 core/modules/macros/contrastcolour.js         | 23 ++++++++++---------
 core/modules/utils/dom/color-utils.js         |  3 +--
 .../contrastcolour/ContrastColourBasic.tid    | 12 ++++++++++
 3 files changed, 25 insertions(+), 13 deletions(-)
 create mode 100644 editions/test/tiddlers/tests/data/macros/contrastcolour/ContrastColourBasic.tid

diff --git a/core/modules/macros/contrastcolour.js b/core/modules/macros/contrastcolour.js
index eab6f0108..6d38993f0 100644
--- a/core/modules/macros/contrastcolour.js
+++ b/core/modules/macros/contrastcolour.js
@@ -29,27 +29,28 @@ exports.params = [
 Run the macro
 */
 exports.run = function(target,fallbackTarget,colourA,colourB) {
-	var rgbTarget = $tw.utils.parseCSSColor(target) || $tw.utils.parseCSSColor(fallbackTarget);
+	var rgbTarget = $tw.utils.parseCSSColorObject(target) || $tw.utils.parseCSSColorObject(fallbackTarget);
 	if(!rgbTarget) {
 		return colourA;
 	}
-	var rgbColourA = $tw.utils.parseCSSColor(colourA),
-		rgbColourB = $tw.utils.parseCSSColor(colourB);
+	var rgbColourA = $tw.utils.parseCSSColorObject(colourA),
+		rgbColourB = $tw.utils.parseCSSColorObject(colourB);
 	if(rgbColourA && !rgbColourB) {
-		return rgbColourA;
+		return colourA;
 	}
 	if(rgbColourB && !rgbColourA) {
-		return rgbColourB;
+		return colourB;
 	}
 	if(!rgbColourA && !rgbColourB) {
 		// If neither colour is readable, return a crude inverse of the target
-		return [255 - rgbTarget[0],255 - rgbTarget[1],255 - rgbTarget[2],rgbTarget[3]];
+		rgbTarget.srgb.r = 1 - rgbTarget.srgb.r;
+		rgbTarget.srgb.g = 1 - rgbTarget.srgb.g;
+		rgbTarget.srgb.b = 1 - rgbTarget.srgb.b;
+		return rgbTarget.display();
 	}
-	// Colour brightness formula derived from http://www.w3.org/WAI/ER/WD-AERT/#color-contrast
-	var brightnessTarget = rgbTarget[0] * 0.299 + rgbTarget[1] * 0.587 + rgbTarget[2] * 0.114,
-		brightnessA = rgbColourA[0] * 0.299 + rgbColourA[1] * 0.587 + rgbColourA[2] * 0.114,
-		brightnessB = rgbColourB[0] * 0.299 + rgbColourB[1] * 0.587 + rgbColourB[2] * 0.114;
-	return Math.abs(brightnessTarget - brightnessA) > Math.abs(brightnessTarget - brightnessB) ? colourA : colourB;
+	var aContrast = rgbColourA.contrast(rgbTarget,"DeltaPhi"),
+		bContrast = rgbColourB.contrast(rgbTarget,"DeltaPhi");
+	return aContrast > bContrast ? colourA : colourB;
 };
 
 })();
diff --git a/core/modules/utils/dom/color-utils.js b/core/modules/utils/dom/color-utils.js
index 74e533a37..475632418 100644
--- a/core/modules/utils/dom/color-utils.js
+++ b/core/modules/utils/dom/color-utils.js
@@ -32,8 +32,7 @@ exports.parseCSSColor = function(colourString) {
 Preferred way to parse a Color.js colour
 */
 exports.parseCSSColorObject = function(colourString) {
-	var Color = require("$:/core/modules/utils/dom/color.js").Color,
-		c = null;
+	var c = null;
 	try {
 		c = new Color(colourString);
 	} catch(e) {
diff --git a/editions/test/tiddlers/tests/data/macros/contrastcolour/ContrastColourBasic.tid b/editions/test/tiddlers/tests/data/macros/contrastcolour/ContrastColourBasic.tid
new file mode 100644
index 000000000..13940f3ed
--- /dev/null
+++ b/editions/test/tiddlers/tests/data/macros/contrastcolour/ContrastColourBasic.tid
@@ -0,0 +1,12 @@
+title: Macros/ContrastColour/ContrastColourBasic
+description: Basic usage of contrastcolour macro
+type: text/vnd.tiddlywiki-multiple
+tags: [[$:/tags/wiki-test-spec]]
+
+title: Output
+
+Colour: <<contrastcolour target:#1e90ff fallbackTarget:#eecc66 colourA:#333333 colourB:#ffffff>>
++
+title: ExpectedResult
+
+<p>Colour: #ffffff</p>
\ No newline at end of file